class BigDecimal

Parent:
Numeric

BigDecimal provides arbitrary-precision floating point decimal arithmetic.

Introduction

Ruby provides built-in support for arbitrary precision integer arithmetic.

For example:

42**13  #=>   1265437718438866624512

BigDecimal provides similar support for very large or very accurate floating point numbers.

Decimal arithmetic is also useful for general calculation, because it provides the correct answers people expect–whereas normal binary floating point arithmetic often introduces subtle errors because of the conversion between base 10 and base 2.

For example, try:

sum = 0
10_000.times do
  sum = sum + 0.0001
end
print sum #=> 0.9999999999999062

and contrast with the output from:

require 'bigdecimal'

sum = BigDecimal.new("0")
10_000.times do
  sum = sum + BigDecimal.new("0.0001")
end
print sum #=> 0.1E1

Similarly:

(BigDecimal.new("1.2") - BigDecimal("1.0")) == BigDecimal("0.2") #=> true

(1.2 - 1.0) == 0.2 #=> false

Special features of accurate decimal arithmetic

Because BigDecimal is more accurate than normal binary floating point arithmetic, it requires some special values.

Infinity

BigDecimal sometimes needs to return infinity, for example if you divide a value by zero.

BigDecimal.new("1.0") / BigDecimal.new("0.0")  #=> Infinity
BigDecimal.new("-1.0") / BigDecimal.new("0.0")  #=> -Infinity

You can represent infinite numbers to BigDecimal using the strings 'Infinity', '+Infinity' and '-Infinity' (case-sensitive)

Not a Number

When a computation results in an undefined value, the special value NaN (for 'not a number') is returned.

Example:

BigDecimal.new("0.0") / BigDecimal.new("0.0") #=> NaN

You can also create undefined values.

NaN is never considered to be the same as any other value, even NaN itself:

n = BigDecimal.new('NaN')
n == 0.0 #=> false
n == n #=> false

Positive and negative zero

If a computation results in a value which is too small to be represented as a BigDecimal within the currently specified limits of precision, zero must be returned.

If the value which is too small to be represented is negative, a BigDecimal value of negative zero is returned.

BigDecimal.new("1.0") / BigDecimal.new("-Infinity") #=> -0.0

If the value is positive, a value of positive zero is returned.

BigDecimal.new("1.0") / BigDecimal.new("Infinity") #=> 0.0

(See ::mode for how to specify limits of precision.)

Note that -0.0 and 0.0 are considered to be the same for the purposes of comparison.

Note also that in mathematics, there is no particular concept of negative or positive zero; true mathematical zero has no sign.

bigdecimal/util

When you require bigdecimal/util, the to_d method will be available on BigDecimal and the native Integer, Float, Rational, and String classes:

require 'bigdecimal/util'

42.to_d         # => 0.42e2
0.5.to_d        # => 0.5e0
(2/3r).to_d(3)  # => 0.667e0
"0.5".to_d      # => 0.5e0

License

Copyright (C) 2002 by Shigeo Kobayashi <[email protected]>.

BigDecimal is released under the Ruby and 2-clause BSD licenses. See LICENSE.txt for details.

Maintained by mrkn <[email protected]> and ruby-core members.

Documented by zzak <[email protected]>, mathew <[email protected]>, and many other contributors.

Constants

BASE

Base value used in internal calculations. On a 32 bit system, BASE is 10000, indicating that calculation is done in groups of 4 digits. (If it were larger, BASE**2 wouldn't fit in 32 bits, so you couldn't guarantee that two groups could always be multiplied together without overflow.)

EXCEPTION_ALL

Determines whether overflow, underflow or zero divide result in an exception being thrown. See ::mode.

EXCEPTION_INFINITY

Determines what happens when the result of a computation is infinity. See ::mode.

EXCEPTION_NaN

Determines what happens when the result of a computation is not a number (NaN). See ::mode.

EXCEPTION_OVERFLOW

Determines what happens when the result of a computation is an overflow (a result too large to be represented). See ::mode.

EXCEPTION_UNDERFLOW

Determines what happens when the result of a computation is an underflow (a result too small to be represented). See ::mode.

EXCEPTION_ZERODIVIDE

Determines what happens when a division by zero is performed. See ::mode.

INFINITY

Positive infinity value.

NAN

'Not a Number' value.

ROUND_CEILING

Round towards +Infinity. See ::mode.

ROUND_DOWN

Indicates that values should be rounded towards zero. See ::mode.

ROUND_FLOOR

Round towards -Infinity. See ::mode.

ROUND_HALF_DOWN

Indicates that digits >= 6 should be rounded up, others rounded down. See ::mode.

ROUND_HALF_EVEN

Round towards the even neighbor. See ::mode.

ROUND_HALF_UP

Indicates that digits >= 5 should be rounded up, others rounded down. See ::mode.

ROUND_MODE

Determines what happens when a result must be rounded in order to fit in the appropriate number of significant digits. See ::mode.

ROUND_UP

Indicates that values should be rounded away from zero. See ::mode.

SIGN_NEGATIVE_FINITE

Indicates that a value is negative and finite. See #sign.

SIGN_NEGATIVE_INFINITE

Indicates that a value is negative and infinite. See #sign.

SIGN_NEGATIVE_ZERO

Indicates that a value is -0. See #sign.

SIGN_NaN

Indicates that a value is not a number. See #sign.

SIGN_POSITIVE_FINITE

Indicates that a value is positive and finite. See #sign.

SIGN_POSITIVE_INFINITE

Indicates that a value is positive and infinite. See #sign.

SIGN_POSITIVE_ZERO

Indicates that a value is +0. See #sign.

Public Class Methods

_load(p1) Show source 
static VALUE
BigDecimal_load(VALUE self, VALUE str)
{
    ENTER(2);
    Real *pv;
    unsigned char *pch;
    unsigned char ch;
    unsigned long m=0;

    pch = (unsigned char *)StringValueCStr(str);
    rb_check_safe_obj(str);
    /* First get max prec */
    while((*pch) != (unsigned char)'\0' && (ch = *pch++) != (unsigned char)':') {
        if(!ISDIGIT(ch)) {
            rb_raise(rb_eTypeError, "load failed: invalid character in the marshaled string");
        }
        m = m*10 + (unsigned long)(ch-'0');
    }
    if (m > VpBaseFig()) m -= VpBaseFig();
    GUARD_OBJ(pv, VpNewRbClass(m, (char *)pch, self));
    m /= VpBaseFig();
    if (m && pv->MaxPrec > m) {
        pv->MaxPrec = m+1;
    }
    return ToValue(pv);
}

Internal method used to provide marshalling support. See the Marshal module.

double_fig Show source 
static VALUE
BigDecimal_double_fig(VALUE self)
{
    return INT2FIX(VpDblFig());
}

The ::double_fig class method returns the number of digits a Float number is allowed to have. The result depends upon the CPU and OS in use.

json_create(object) Show source 
# File ext/json/lib/json/add/bigdecimal.rb, line 11
def self.json_create(object)
  BigDecimal._load object['b']
end

Import a JSON Marshalled object.

method used for JSON marshalling support.

limit(digits) Show source 
static VALUE
BigDecimal_limit(int argc, VALUE *argv, VALUE self)
{
    VALUE  nFig;
    VALUE  nCur = INT2NUM(VpGetPrecLimit());

    if (rb_scan_args(argc, argv, "01", &nFig) == 1) {
        int nf;
        if (NIL_P(nFig)) return nCur;
        nf = NUM2INT(nFig);
        if (nf < 0) {
            rb_raise(rb_eArgError, "argument must be positive");
        }
        VpSetPrecLimit(nf);
    }
    return nCur;
}

Limit the number of significant digits in newly created BigDecimal numbers to the specified value. Rounding is performed as necessary, as specified by ::mode.

A limit of 0, the default, means no upper limit.

The limit specified by this method takes less priority over any limit specified to instance methods such as ceil, floor, truncate, or round.

mode(mode, value) Show source 
static VALUE
BigDecimal_mode(int argc, VALUE *argv, VALUE self)
{
    VALUE which;
    VALUE val;
    unsigned long f,fo;

    rb_scan_args(argc, argv, "11", &which, &val);
    f = (unsigned long)NUM2INT(which);

    if (f & VP_EXCEPTION_ALL) {
        /* Exception mode setting */
        fo = VpGetException();
        if (val == Qnil) return INT2FIX(fo);
        if (val != Qfalse && val!=Qtrue) {
            rb_raise(rb_eArgError, "second argument must be true or false");
            return Qnil; /* Not reached */
        }
        if (f & VP_EXCEPTION_INFINITY) {
            VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_INFINITY) :
                        (fo & (~VP_EXCEPTION_INFINITY))));
        }
        fo = VpGetException();
        if (f & VP_EXCEPTION_NaN) {
            VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_NaN) :
                        (fo & (~VP_EXCEPTION_NaN))));
        }
        fo = VpGetException();
        if (f & VP_EXCEPTION_UNDERFLOW) {
            VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_UNDERFLOW) :
                        (fo & (~VP_EXCEPTION_UNDERFLOW))));
        }
        fo = VpGetException();
        if(f & VP_EXCEPTION_ZERODIVIDE) {
            VpSetException((unsigned short)((val == Qtrue) ? (fo | VP_EXCEPTION_ZERODIVIDE) :
                        (fo & (~VP_EXCEPTION_ZERODIVIDE))));
        }
        fo = VpGetException();
        return INT2FIX(fo);
    }
    if (VP_ROUND_MODE == f) {
        /* Rounding mode setting */
        unsigned short sw;
        fo = VpGetRoundMode();
        if (NIL_P(val)) return INT2FIX(fo);
        sw = check_rounding_mode(val);
        fo = VpSetRoundMode(sw);
        return INT2FIX(fo);
    }
    rb_raise(rb_eTypeError, "first argument for BigDecimal.mode invalid");
    return Qnil;
}

Controls handling of arithmetic exceptions and rounding. If no value is supplied, the current value is returned.

Six values of the mode parameter control the handling of arithmetic exceptions:

BigDecimal::EXCEPTION_NaN BigDecimal::EXCEPTION_INFINITY BigDecimal::EXCEPTION_UNDERFLOW BigDecimal::EXCEPTION_OVERFLOW BigDecimal::EXCEPTION_ZERODIVIDE BigDecimal::EXCEPTION_ALL

For each mode parameter above, if the value set is false, computation continues after an arithmetic exception of the appropriate type. When computation continues, results are as follows:

EXCEPTION_NaN

NaN

EXCEPTION_INFINITY

+Infinity or -Infinity

EXCEPTION_UNDERFLOW

0

EXCEPTION_OVERFLOW

+Infinity or -Infinity

EXCEPTION_ZERODIVIDE

+Infinity or -Infinity

One value of the mode parameter controls the rounding of numeric values: BigDecimal::ROUND_MODE. The values it can take are:

ROUND_UP, :up

round away from zero

ROUND_DOWN, :down, :truncate

round towards zero (truncate)

ROUND_HALF_UP, :half_up, :default

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round away from zero. (default)

ROUND_HALF_DOWN, :half_down

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards zero.

ROUND_HALF_EVEN, :half_even, :banker

round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards the even neighbor (Banker's rounding)

ROUND_CEILING, :ceiling, :ceil

round towards positive infinity (ceil)

ROUND_FLOOR, :floor

round towards negative infinity (floor)

new(initial, digits) Show source 
static VALUE
BigDecimal_initialize(int argc, VALUE *argv, VALUE self)
{
    ENTER(1);
    Real *pv = rb_check_typeddata(self, &BigDecimal_data_type);
    Real *x;

    GUARD_OBJ(x, BigDecimal_new(argc, argv));
    if (ToValue(x)) {
        pv = VpCopy(pv, x);
    }
    else {
        VpFree(pv);
        pv = x;
    }
    DATA_PTR(self) = pv;
    pv->obj = self;
    return self;
}

Create a new BigDecimal object.

initial

The initial value, as an Integer, a Float, a Rational, a BigDecimal, or a String.

If it is a String, spaces are ignored and unrecognized characters terminate the value.

digits

The number of significant digits, as an Integer. If omitted or 0, the number of significant digits is determined from the initial value.

The actual number of significant digits used in computation is usually larger than the specified number.

Exceptions

TypeError

If the initial type is neither Integer, Float, Rational, nor BigDecimal, this exception is raised.

TypeError

If the digits is not an Integer, this exception is raised.

ArgumentError

If initial is a Float, and the digits is larger than Float::DIG + 1, this exception is raised.

ArgumentError

If the initial is a Float or Rational, and the digits value is omitted, this exception is raised.

save_exception_mode { ... } Show source 
static VALUE
BigDecimal_save_exception_mode(VALUE self)
{
    unsigned short const exception_mode = VpGetException();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetException(exception_mode);
    if (state) rb_jump_tag(state);
    return ret;
}

Execute the provided block, but preserve the exception mode

BigDecimal.save_exception_mode do
  BigDecimal.mode(BigDecimal::EXCEPTION_OVERFLOW, false)
  BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)

  BigDecimal.new(BigDecimal('Infinity'))
  BigDecimal.new(BigDecimal('-Infinity'))
  BigDecimal(BigDecimal.new('NaN'))
end

For use with the BigDecimal::EXCEPTION_*

See ::mode

save_limit { ... } Show source 
static VALUE
BigDecimal_save_limit(VALUE self)
{
    size_t const limit = VpGetPrecLimit();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetPrecLimit(limit);
    if (state) rb_jump_tag(state);
    return ret;
}

Execute the provided block, but preserve the precision limit

BigDecimal.limit(100)
puts BigDecimal.limit
BigDecimal.save_limit do
    BigDecimal.limit(200)
    puts BigDecimal.limit
end
puts BigDecimal.limit
save_rounding_mode { ... } Show source 
static VALUE
BigDecimal_save_rounding_mode(VALUE self)
{
    unsigned short const round_mode = VpGetRoundMode();
    int state;
    VALUE ret = rb_protect(rb_yield, Qnil, &state);
    VpSetRoundMode(round_mode);
    if (state) rb_jump_tag(state);
    return ret;
}

Execute the provided block, but preserve the rounding mode

BigDecimal.save_rounding_mode do
  BigDecimal.mode(BigDecimal::ROUND_MODE, :up)
  puts BigDecimal.mode(BigDecimal::ROUND_MODE)
end

For use with the BigDecimal::ROUND_*

See ::mode

ver() Show source 
static VALUE
BigDecimal_version(VALUE self)
{
    /*
     * 1.0.0: Ruby 1.8.0
     * 1.0.1: Ruby 1.8.1
     * 1.1.0: Ruby 1.9.3
    */
    return rb_str_new2("1.1.0");
}

Returns the BigDecimal version number.

Public Instance Methods

a % b Show source 
static VALUE
BigDecimal_mod(VALUE self, VALUE r)

Returns the modulus from dividing by b.

See #divmod.

mult(value, digits) Show source 
static VALUE
BigDecimal_mult(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    if (RB_TYPE_P(r, T_FLOAT)) {
        b = GetVpValueWithPrec(r, DBL_DIG+1, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
        b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
        b = GetVpValue(r,0);
    }

    if (!b) return DoSomeOne(self, r, '*');
    SAVE(b);

    mx = a->Prec + b->Prec;
    GUARD_OBJ(c, VpCreateRbObject(mx *(VpBaseFig() + 1), "0"));
    VpMult(c, a, b);
    return ToValue(c);
}

Multiply by the specified value.

e.g.

c = a.mult(b,n)
c = a * b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

a ** n → bigdecimal Show source 
static VALUE
BigDecimal_power_op(VALUE self, VALUE exp)
{
    return BigDecimal_power(1, &exp, self);
}

Returns the value raised to the power of n.

See #power.

add(value, digits) Show source 
static VALUE
BigDecimal_add(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    if (RB_TYPE_P(r, T_FLOAT)) {
        b = GetVpValueWithPrec(r, DBL_DIG+1, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
        b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
        b = GetVpValue(r, 0);
    }

    if (!b) return DoSomeOne(self,r,'+');
    SAVE(b);

    if (VpIsNaN(b)) return b->obj;
    if (VpIsNaN(a)) return a->obj;

    mx = GetAddSubPrec(a, b);
    if (mx == (size_t)-1L) {
        GUARD_OBJ(c,VpCreateRbObject(VpBaseFig() + 1, "0"));
        VpAddSub(c, a, b, 1);
    }
    else {
        GUARD_OBJ(c, VpCreateRbObject(mx * (VpBaseFig() + 1), "0"));
        if(!mx) {
            VpSetInf(c, VpGetSign(a));
        }
        else {
            VpAddSub(c, a, b, 1);
        }
    }
    return ToValue(c);
}

Add the specified value.

e.g.

c = a.add(b,n)
c = a + b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

+big_decimal → big_decimal Show source 
static VALUE
BigDecimal_uplus(VALUE self)
{
    return self;
}

Return self.

+BigDecimal('5')  #=> 0.5e1
a - b → bigdecimal Show source 
static VALUE
BigDecimal_sub(VALUE self, VALUE r)
{
    ENTER(5);
    Real *c, *a, *b;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self,1));
    if (RB_TYPE_P(r, T_FLOAT)) {
        b = GetVpValueWithPrec(r, DBL_DIG+1, 1);
    }
    else if (RB_TYPE_P(r, T_RATIONAL)) {
        b = GetVpValueWithPrec(r, a->Prec*VpBaseFig(), 1);
    }
    else {
        b = GetVpValue(r,0);
    }

    if (!b) return DoSomeOne(self,r,'-');
    SAVE(b);

    if (VpIsNaN(b)) return b->obj;
    if (VpIsNaN(a)) return a->obj;

    mx = GetAddSubPrec(a,b);
    if (mx == (size_t)-1L) {
        GUARD_OBJ(c,VpCreateRbObject(VpBaseFig() + 1, "0"));
        VpAddSub(c, a, b, -1);
    }
    else {
        GUARD_OBJ(c,VpCreateRbObject(mx *(VpBaseFig() + 1), "0"));
        if (!mx) {
            VpSetInf(c,VpGetSign(a));
        }
        else {
            VpAddSub(c, a, b, -1);
        }
    }
    return ToValue(c);
}

Subtract the specified value.

e.g.

c = a - b

The precision of the result value depends on the type of b.

If b is a Float, the precision of the result is Float::DIG+1.

If b is a BigDecimal, the precision of the result is b's precision of internal representation from platform. So, it's return value is platform dependent.

-big_decimal → big_decimal Show source 
static VALUE
BigDecimal_neg(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    GUARD_OBJ(a, GetVpValue(self, 1));
    GUARD_OBJ(c, VpCreateRbObject(a->Prec *(VpBaseFig() + 1), "0"));
    VpAsgn(c, a, -1);
    return ToValue(c);
}

Return the negation of self.

-BigDecimal('5')  #=> -0.5e1
a / b → bigdecimal Show source 
static VALUE
BigDecimal_div(VALUE self, VALUE r)
/* For c = self/r: with round operation */
{
    ENTER(5);
    Real *c=NULL, *res=NULL, *div = NULL;
    r = BigDecimal_divide(&c, &res, &div, self, r);
    if (!NIL_P(r)) return r; /* coerced by other */
    SAVE(c); SAVE(res); SAVE(div);
    /* a/b = c + r/b */
    /* c xxxxx
       r 00000yyyyy  ==> (y/b)*BASE >= HALF_BASE
     */
    /* Round */
    if (VpHasVal(div)) { /* frac[0] must be zero for NaN,INF,Zero */
        VpInternalRound(c, 0, c->frac[c->Prec-1], (BDIGIT)(VpBaseVal() * (BDIGIT_DBL)res->frac[0] / div->frac[0]));
    }
    return ToValue(c);
}

Divide by the specified value.

See #div.

a < b Show source 
static VALUE
BigDecimal_lt(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '<');
}

Returns true if a is less than b.

Values may be coerced to perform the comparison (see ==, #coerce).

a <= b Show source 
static VALUE
BigDecimal_le(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, 'L');
}

Returns true if a is less than or equal to b.

Values may be coerced to perform the comparison (see ==, #coerce).

<=>(p1) Show source 
static VALUE
BigDecimal_comp(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '*');
}

The comparison operator. a <=> b is 0 if a == b, 1 if a > b, -1 if a < b.

==(p1) Show source 
static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal.new('1.0') == 1.0  #=> true
===(p1) Show source 
static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal.new('1.0') == 1.0  #=> true
a > b Show source 
static VALUE
BigDecimal_gt(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '>');
}

Returns true if a is greater than b.

Values may be coerced to perform the comparison (see ==, #coerce).

a >= b Show source 
static VALUE
BigDecimal_ge(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, 'G');
}

Returns true if a is greater than or equal to b.

Values may be coerced to perform the comparison (see ==, #coerce)

_dump Show source 
static VALUE
BigDecimal_dump(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *vp;
    char *psz;
    VALUE dummy;
    volatile VALUE dump;

    rb_scan_args(argc, argv, "01", &dummy);
    GUARD_OBJ(vp,GetVpValue(self, 1));
    dump = rb_str_new(0, VpNumOfChars(vp, "E")+50);
    psz = RSTRING_PTR(dump);
    sprintf(psz, "%"PRIuSIZE":", VpMaxPrec(vp)*VpBaseFig());
    VpToString(vp, psz+strlen(psz), 0, 0);
    rb_str_resize(dump, strlen(psz));
    return dump;
}

Method used to provide marshalling support.

inf = BigDecimal.new('Infinity')
  #=> Infinity
BigDecimal._load(inf._dump)
  #=> Infinity

See the Marshal module.

abs → big_decimal Show source 
static VALUE
BigDecimal_abs(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec *(VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpAsgn(c, a, 1);
    VpChangeSign(c, 1);
    return ToValue(c);
}

Returns the absolute value, as a BigDecimal.

BigDecimal('5').abs  #=> 0.5e1
BigDecimal('-3').abs #=> 0.3e1
add(value, digits) Show source 
static VALUE
BigDecimal_add2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPositiveInt(n);
    if (mx == 0) return BigDecimal_add(self, b);
    else {
        size_t pl = VpSetPrecLimit(0);
        VALUE   c = BigDecimal_add(self, b);
        VpSetPrecLimit(pl);
        GUARD_OBJ(cv, GetVpValue(c, 1));
        VpLeftRound(cv, VpGetRoundMode(), mx);
        return ToValue(cv);
    }
}
+

Add the specified value.

e.g.

c = a.add(b,n)
c = a + b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

as_json(*) Show source 
# File ext/json/lib/json/add/bigdecimal.rb, line 18
def as_json(*)
  {
    JSON.create_id => self.class.name,
    'b'            => _dump,
  }
end

Marshal the object to JSON.

method used for JSON marshalling support.

ceil(n) Show source 
static VALUE
BigDecimal_ceil(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc) == 0) {
        iLoc = 0;
    } else {
        iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_CEIL, iLoc);
    if (argc == 0) {
        return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

Return the smallest integer greater than or equal to the value, as a BigDecimal.

BigDecimal('3.14159').ceil #=> 4
BigDecimal('-9.1').ceil #=> -9

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').ceil(3) #=> 3.142
BigDecimal('13345.234').ceil(-2) #=> 13400.0
coerce(p1) Show source 
static VALUE
BigDecimal_coerce(VALUE self, VALUE other)
{
    ENTER(2);
    VALUE obj;
    Real *b;

    if (RB_TYPE_P(other, T_FLOAT)) {
        GUARD_OBJ(b, GetVpValueWithPrec(other, DBL_DIG+1, 1));
        obj = rb_assoc_new(ToValue(b), self);
    }
    else {
        if (RB_TYPE_P(other, T_RATIONAL)) {
            Real* pv = DATA_PTR(self);
            GUARD_OBJ(b, GetVpValueWithPrec(other, pv->Prec*VpBaseFig(), 1));
        }
        else {
            GUARD_OBJ(b, GetVpValue(other, 1));
        }
        obj = rb_assoc_new(b->obj, self);
    }

    return obj;
}

The coerce method provides support for Ruby type coercion. It is not enabled by default.

This means that binary operations like + * / or - can often be performed on a BigDecimal and an object of another type, if the other object can be coerced into a BigDecimal value.

e.g.

a = BigDecimal.new("1.0")
b = a / 2.0 #=> 0.5

Note that coercing a String to a BigDecimal is not supported by default; it requires a special compile-time option when building Ruby.

div(value, digits) → bigdecimal or integer Show source 
static VALUE
BigDecimal_div3(int argc, VALUE *argv, VALUE self)
{
    VALUE b,n;

    rb_scan_args(argc, argv, "11", &b, &n);

    return BigDecimal_div2(self, b, n);
}

Divide by the specified value.

digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

If digits is 0, the result is the same as for the / operator or quo.

If digits is not specified, the result is an integer, by analogy with Numeric#div; see also #divmod.

Examples:

a = BigDecimal("4")
b = BigDecimal("3")

a.div(b, 3)  # => 0.133e1

a.div(b, 0)  # => 0.1333333333333333333e1
a / b        # => 0.1333333333333333333e1
a.quo(b)     # => 0.1333333333333333333e1

a.div(b)     # => 1
divmod(value) Show source 
static VALUE
BigDecimal_divmod(VALUE self, VALUE r)
{
    ENTER(5);
    Real *div = NULL, *mod = NULL;

    if (BigDecimal_DoDivmod(self, r, &div, &mod)) {
        SAVE(div); SAVE(mod);
        return rb_assoc_new(ToValue(div), ToValue(mod));
    }
    return DoSomeOne(self,r,rb_intern("divmod"));
}

Divides by the specified value, and returns the quotient and modulus as BigDecimal numbers. The quotient is rounded towards negative infinity.

For example:

require 'bigdecimal'

a = BigDecimal.new("42")
b = BigDecimal.new("9")

q, m = a.divmod(b)

c = q * b + m

a == c  #=> true

The quotient q is (a/b).floor, and the modulus is the amount that must be added to q * b to get a.

eql?(p1) Show source 
static VALUE
BigDecimal_eq(VALUE self, VALUE r)
{
    return BigDecimalCmp(self, r, '=');
}

Tests for value equality; returns true if the values are equal.

The == and === operators and the eql? method have the same implementation for BigDecimal.

Values may be coerced to perform the comparison:

BigDecimal.new('1.0') == 1.0  #=> true
exponent() Show source 
static VALUE
BigDecimal_exponent(VALUE self)
{
    ssize_t e = VpExponent10(GetVpValue(self, 1));
    return INT2NUM(e);
}

Returns the exponent of the BigDecimal number, as an Integer.

If the number can be represented as 0.xxxxxx*10**n where xxxxxx is a string of digits with no leading zeros, then n is the exponent.

finite?() Show source 
static VALUE
BigDecimal_IsFinite(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsNaN(p)) return Qfalse;
    if (VpIsInf(p)) return Qfalse;
    return Qtrue;
}

Returns True if the value is finite (not NaN or infinite).

fix() Show source 
static VALUE
BigDecimal_fix(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec *(VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpActiveRound(c, a, VP_ROUND_DOWN, 0); /* 0: round off */
    return ToValue(c);
}

Return the integer part of the number, as a BigDecimal.

floor(n) Show source 
static VALUE
BigDecimal_floor(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc)==0) {
        iLoc = 0;
    }
    else {
        iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_FLOOR, iLoc);
#ifdef BIGDECIMAL_DEBUG
    VPrint(stderr, "floor: c=%\n", c);
#endif
    if (argc == 0) {
        return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

Return the largest integer less than or equal to the value, as a BigDecimal.

BigDecimal('3.14159').floor #=> 3
BigDecimal('-9.1').floor #=> -10

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').floor(3) #=> 3.141
BigDecimal('13345.234').floor(-2) #=> 13300.0
frac() Show source 
static VALUE
BigDecimal_frac(VALUE self)
{
    ENTER(5);
    Real *c, *a;
    size_t mx;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpFrac(c, a);
    return ToValue(c);
}

Return the fractional part of the number, as a BigDecimal.

static VALUE
BigDecimal_hash(VALUE self)
{
    ENTER(1);
    Real *p;
    st_index_t hash;

    GUARD_OBJ(p, GetVpValue(self, 1));
    hash = (st_index_t)p->sign;
    /* hash!=2: the case for 0(1),NaN(0) or +-Infinity(3) is sign itself */
    if(hash == 2 || hash == (st_index_t)-2) {
        hash ^= rb_memhash(p->frac, sizeof(BDIGIT)*p->Prec);
        hash += p->exponent;
    }
    return ST2FIX(hash);
}

Creates a hash for this BigDecimal.

Two BigDecimals with equal sign, fractional part and exponent have the same hash.

infinite?() Show source 
static VALUE
BigDecimal_IsInfinite(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsPosInf(p)) return INT2FIX(1);
    if (VpIsNegInf(p)) return INT2FIX(-1);
    return Qnil;
}

Returns nil, -1, or +1 depending on whether the value is finite, -Infinity, or +Infinity.

inspect() Show source 
static VALUE
BigDecimal_inspect(VALUE self)
{
    ENTER(5);
    Real *vp;
    volatile VALUE str;
    size_t nc;

    GUARD_OBJ(vp, GetVpValue(self, 1));
    nc = VpNumOfChars(vp, "E");

    str = rb_str_new(0, nc);
    VpToString(vp, RSTRING_PTR(str), 0, 0);
    rb_str_resize(str, strlen(RSTRING_PTR(str)));
    return str;
}

Returns debugging information about the value as a string of comma-separated values in angle brackets with a leading #:

BigDecimal.new("1234.5678").inspect
  #=> "0.12345678e4"

The first part is the address, the second is the value as a string, and the final part ss(mm) is the current number of significant digits and the maximum number of significant digits, respectively.

modulo(b) Show source 
static VALUE
BigDecimal_mod(VALUE self, VALUE r)

Returns the modulus from dividing by b.

See #divmod.

mult(value, digits) Show source 
static VALUE
BigDecimal_mult2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPositiveInt(n);
    if (mx == 0) return BigDecimal_mult(self, b);
    else {
        size_t pl = VpSetPrecLimit(0);
        VALUE   c = BigDecimal_mult(self, b);
        VpSetPrecLimit(pl);
        GUARD_OBJ(cv, GetVpValue(c, 1));
        VpLeftRound(cv, VpGetRoundMode(), mx);
        return ToValue(cv);
    }
}

Multiply by the specified value.

e.g.

c = a.mult(b,n)
c = a * b
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

nan?() Show source 
static VALUE
BigDecimal_IsNaN(VALUE self)
{
    Real *p = GetVpValue(self, 1);
    if (VpIsNaN(p))  return Qtrue;
    return Qfalse;
}

Returns True if the value is Not a Number.

nonzero?() Show source 
static VALUE
BigDecimal_nonzero(VALUE self)
{
    Real *a = GetVpValue(self, 1);
    return VpIsZero(a) ? Qnil : self;
}

Returns self if the value is non-zero, nil otherwise.

power(n) Show source
power(n, prec) 
static VALUE
BigDecimal_power(int argc, VALUE*argv, VALUE self)
{
    ENTER(5);
    VALUE vexp, prec;
    Real* exp = NULL;
    Real *x, *y;
    ssize_t mp, ma, n;
    SIGNED_VALUE int_exp;
    double d;

    rb_scan_args(argc, argv, "11", &vexp, &prec);

    GUARD_OBJ(x, GetVpValue(self, 1));
    n = NIL_P(prec) ? (ssize_t)(x->Prec*VpBaseFig()) : NUM2SSIZET(prec);

    if (VpIsNaN(x)) {
        y = VpCreateRbObject(n, "0#");
        RB_GC_GUARD(y->obj);
        VpSetNaN(y);
        return ToValue(y);
    }

  retry:
    switch (TYPE(vexp)) {
      case T_FIXNUM:
        break;

      case T_BIGNUM:
        break;

      case T_FLOAT:
        d = RFLOAT_VALUE(vexp);
        if (d == round(d)) {
            if (FIXABLE(d)) {
                vexp = LONG2FIX((long)d);
            }
            else {
                vexp = rb_dbl2big(d);
            }
            goto retry;
        }
        exp = GetVpValueWithPrec(vexp, DBL_DIG+1, 1);
        break;

      case T_RATIONAL:
        if (is_zero(rb_rational_num(vexp))) {
            if (is_positive(vexp)) {
                vexp = INT2FIX(0);
                goto retry;
            }
        }
        else if (is_one(rb_rational_den(vexp))) {
            vexp = rb_rational_num(vexp);
            goto retry;
        }
        exp = GetVpValueWithPrec(vexp, n, 1);
        break;

      case T_DATA:
        if (is_kind_of_BigDecimal(vexp)) {
            VALUE zero = INT2FIX(0);
            VALUE rounded = BigDecimal_round(1, &zero, vexp);
            if (RTEST(BigDecimal_eq(vexp, rounded))) {
                vexp = BigDecimal_to_i(vexp);
                goto retry;
            }
            exp = DATA_PTR(vexp);
            break;
        }
        /* fall through */
      default:
        rb_raise(rb_eTypeError,
                 "wrong argument type %"PRIsVALUE" (expected scalar Numeric)",
                 RB_OBJ_CLASSNAME(vexp));
    }

    if (VpIsZero(x)) {
        if (is_negative(vexp)) {
            y = VpCreateRbObject(n, "#0");
            RB_GC_GUARD(y->obj);
            if (BIGDECIMAL_NEGATIVE_P(x)) {
                if (is_integer(vexp)) {
                    if (is_even(vexp)) {
                        /* (-0) ** (-even_integer)  -> Infinity */
                        VpSetPosInf(y);
                    }
                    else {
                        /* (-0) ** (-odd_integer)  -> -Infinity */
                        VpSetNegInf(y);
                    }
                }
                else {
                    /* (-0) ** (-non_integer)  -> Infinity */
                    VpSetPosInf(y);
                }
            }
            else {
                /* (+0) ** (-num)  -> Infinity */
                VpSetPosInf(y);
            }
            return ToValue(y);
        }
        else if (is_zero(vexp)) {
            return ToValue(VpCreateRbObject(n, "1"));
        }
        else {
            return ToValue(VpCreateRbObject(n, "0"));
        }
    }

    if (is_zero(vexp)) {
        return ToValue(VpCreateRbObject(n, "1"));
    }
    else if (is_one(vexp)) {
        return self;
    }

    if (VpIsInf(x)) {
        if (is_negative(vexp)) {
            if (BIGDECIMAL_NEGATIVE_P(x)) {
                if (is_integer(vexp)) {
                    if (is_even(vexp)) {
                        /* (-Infinity) ** (-even_integer) -> +0 */
                        return ToValue(VpCreateRbObject(n, "0"));
                    }
                    else {
                        /* (-Infinity) ** (-odd_integer) -> -0 */
                        return ToValue(VpCreateRbObject(n, "-0"));
                    }
                }
                else {
                    /* (-Infinity) ** (-non_integer) -> -0 */
                    return ToValue(VpCreateRbObject(n, "-0"));
                }
            }
            else {
                return ToValue(VpCreateRbObject(n, "0"));
            }
        }
        else {
            y = VpCreateRbObject(n, "0#");
            if (BIGDECIMAL_NEGATIVE_P(x)) {
                if (is_integer(vexp)) {
                    if (is_even(vexp)) {
                        VpSetPosInf(y);
                    }
                    else {
                        VpSetNegInf(y);
                    }
                }
                else {
                    /* TODO: support complex */
                    rb_raise(rb_eMathDomainError,
                             "a non-integral exponent for a negative base");
                }
            }
            else {
                VpSetPosInf(y);
            }
            return ToValue(y);
        }
    }

    if (exp != NULL) {
        return rmpd_power_by_big_decimal(x, exp, n);
    }
    else if (RB_TYPE_P(vexp, T_BIGNUM)) {
        VALUE abs_value = BigDecimal_abs(self);
        if (is_one(abs_value)) {
            return ToValue(VpCreateRbObject(n, "1"));
        }
        else if (RTEST(rb_funcall(abs_value, '<', 1, INT2FIX(1)))) {
            if (is_negative(vexp)) {
                y = VpCreateRbObject(n, "0#");
                if (is_even(vexp)) {
                    VpSetInf(y, VpGetSign(x));
                }
                else {
                    VpSetInf(y, -VpGetSign(x));
                }
                return ToValue(y);
            }
            else if (BIGDECIMAL_NEGATIVE_P(x) && is_even(vexp)) {
                return ToValue(VpCreateRbObject(n, "-0"));
            }
            else {
                return ToValue(VpCreateRbObject(n, "0"));
            }
        }
        else {
            if (is_positive(vexp)) {
                y = VpCreateRbObject(n, "0#");
                if (is_even(vexp)) {
                    VpSetInf(y, VpGetSign(x));
                }
                else {
                    VpSetInf(y, -VpGetSign(x));
                }
                return ToValue(y);
            }
            else if (BIGDECIMAL_NEGATIVE_P(x) && is_even(vexp)) {
                return ToValue(VpCreateRbObject(n, "-0"));
            }
            else {
                return ToValue(VpCreateRbObject(n, "0"));
            }
        }
    }

    int_exp = FIX2LONG(vexp);
    ma = int_exp;
    if (ma <  0) ma = -ma;
    if (ma == 0) ma = 1;

    if (VpIsDef(x)) {
        mp = x->Prec * (VpBaseFig() + 1);
        GUARD_OBJ(y, VpCreateRbObject(mp * (ma + 1), "0"));
    }
    else {
        GUARD_OBJ(y, VpCreateRbObject(1, "0"));
    }
    VpPower(y, x, int_exp);
    if (!NIL_P(prec) && VpIsDef(y)) {
        VpMidRound(y, VpGetRoundMode(), n);
    }
    return ToValue(y);
}

Returns the value raised to the power of n.

Note that n must be an Integer.

Also available as the operator **.

precs → array Show source 
static VALUE
BigDecimal_prec(VALUE self)
{
    ENTER(1);
    Real *p;
    VALUE obj;

    GUARD_OBJ(p, GetVpValue(self, 1));
    obj = rb_assoc_new(INT2NUM(p->Prec*VpBaseFig()),
                       INT2NUM(p->MaxPrec*VpBaseFig()));
    return obj;
}

Returns an Array of two Integer values.

The first value is the current number of significant digits in the BigDecimal. The second value is the maximum number of significant digits for the BigDecimal.

BigDecimal('5').precs #=> [9, 18]
quo(value) → bigdecimal Show source 
static VALUE
BigDecimal_div(VALUE self, VALUE r)
/* For c = self/r: with round operation */
{
    ENTER(5);
    Real *c=NULL, *res=NULL, *div = NULL;
    r = BigDecimal_divide(&c, &res, &div, self, r);
    if (!NIL_P(r)) return r; /* coerced by other */
    SAVE(c); SAVE(res); SAVE(div);
    /* a/b = c + r/b */
    /* c xxxxx
       r 00000yyyyy  ==> (y/b)*BASE >= HALF_BASE
     */
    /* Round */
    if (VpHasVal(div)) { /* frac[0] must be zero for NaN,INF,Zero */
        VpInternalRound(c, 0, c->frac[c->Prec-1], (BDIGIT)(VpBaseVal() * (BDIGIT_DBL)res->frac[0] / div->frac[0]));
    }
    return ToValue(c);
}

Divide by the specified value.

See #div.

remainder(value) Show source 
static VALUE
BigDecimal_remainder(VALUE self, VALUE r) /* remainder */
{
    VALUE  f;
    Real  *d, *rv = 0;
    f = BigDecimal_divremain(self, r, &d, &rv);
    if (!NIL_P(f)) return f;
    return ToValue(rv);
}

Returns the remainder from dividing by the value.

x.remainder(y) means x-y*(x/y).truncate

round(n, mode) Show source 
static VALUE
BigDecimal_round(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real   *c, *a;
    int    iLoc = 0;
    VALUE  vLoc;
    VALUE  vRound;
    size_t mx, pl;

    unsigned short sw = VpGetRoundMode();

    switch (rb_scan_args(argc, argv, "02", &vLoc, &vRound)) {
      case 0:
        iLoc = 0;
        break;
      case 1:
        if (RB_TYPE_P(vLoc, T_HASH)) {
            sw = check_rounding_mode_option(vLoc);
        }
        else {
            iLoc = NUM2INT(vLoc);
        }
        break;
      case 2:
        iLoc = NUM2INT(vLoc);
        if (RB_TYPE_P(vRound, T_HASH)) {
            sw = check_rounding_mode_option(vRound);
        }
        else {
            sw = check_rounding_mode(vRound);
        }
        break;
      default:
        break;
    }

    pl = VpSetPrecLimit(0);
    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, sw, iLoc);
    if (argc == 0) {
        return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

Round to the nearest integer (by default), returning the result as a BigDecimal.

BigDecimal('3.14159').round #=> 3
BigDecimal('8.7').round #=> 9
BigDecimal('-9.9').round #=> -10

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').round(3) #=> 3.142
BigDecimal('13345.234').round(-2) #=> 13300.0

The value of the optional mode argument can be used to determine how rounding is performed; see ::mode.

sign() Show source 
static VALUE
BigDecimal_sign(VALUE self)
{ /* sign */
    int s = GetVpValue(self, 1)->sign;
    return INT2FIX(s);
}

Returns the sign of the value.

Returns a positive value if > 0, a negative value if < 0, and a zero if == 0.

The specific value returned indicates the type and sign of the BigDecimal, as follows:

BigDecimal::SIGN_NaN

value is Not a Number

BigDecimal::SIGN_POSITIVE_ZERO

value is +0

BigDecimal::SIGN_NEGATIVE_ZERO

value is -0

BigDecimal::SIGN_POSITIVE_INFINITE

value is +Infinity

BigDecimal::SIGN_NEGATIVE_INFINITE

value is -Infinity

BigDecimal::SIGN_POSITIVE_FINITE

value is positive

BigDecimal::SIGN_NEGATIVE_FINITE

value is negative

split() Show source 
static VALUE
BigDecimal_split(VALUE self)
{
    ENTER(5);
    Real *vp;
    VALUE obj,str;
    ssize_t e, s;
    char *psz1;

    GUARD_OBJ(vp, GetVpValue(self, 1));
    str = rb_str_new(0, VpNumOfChars(vp, "E"));
    psz1 = RSTRING_PTR(str);
    VpSzMantissa(vp, psz1);
    s = 1;
    if(psz1[0] == '-') {
        size_t len = strlen(psz1 + 1);

        memmove(psz1, psz1 + 1, len);
        psz1[len] = '\0';
        s = -1;
    }
    if (psz1[0] == 'N') s = 0; /* NaN */
    e = VpExponent10(vp);
    obj = rb_ary_new2(4);
    rb_ary_push(obj, INT2FIX(s));
    rb_ary_push(obj, str);
    rb_str_resize(str, strlen(psz1));
    rb_ary_push(obj, INT2FIX(10));
    rb_ary_push(obj, INT2NUM(e));
    return obj;
}

Splits a BigDecimal number into four parts, returned as an array of values.

The first value represents the sign of the BigDecimal, and is -1 or 1, or 0 if the BigDecimal is Not a Number.

The second value is a string representing the significant digits of the BigDecimal, with no leading zeros.

The third value is the base used for arithmetic (currently always 10) as an Integer.

The fourth value is an Integer exponent.

If the BigDecimal can be represented as 0.xxxxxx*10**n, then xxxxxx is the string of significant digits with no leading zeros, and n is the exponent.

From these values, you can translate a BigDecimal to a float as follows:

sign, significant_digits, base, exponent = a.split
f = sign * "0.#{significant_digits}".to_f * (base ** exponent)

(Note that the #to_f method is provided as a more convenient way to translate a BigDecimal to a Float.)

sqrt(n) Show source 
static VALUE
BigDecimal_sqrt(VALUE self, VALUE nFig)
{
    ENTER(5);
    Real *c, *a;
    size_t mx, n;

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);

    n = GetPositiveInt(nFig) + VpDblFig() + BASE_FIG;
    if (mx <= n) mx = n;
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSqrt(c, a);
    return ToValue(c);
}

Returns the square root of the value.

Result has at least n significant digits.

sub(value, digits) → bigdecimal Show source 
static VALUE
BigDecimal_sub2(VALUE self, VALUE b, VALUE n)
{
    ENTER(2);
    Real *cv;
    SIGNED_VALUE mx = GetPositiveInt(n);
    if (mx == 0) return BigDecimal_sub(self, b);
    else {
        size_t pl = VpSetPrecLimit(0);
        VALUE   c = BigDecimal_sub(self, b);
        VpSetPrecLimit(pl);
        GUARD_OBJ(cv, GetVpValue(c, 1));
        VpLeftRound(cv, VpGetRoundMode(), mx);
        return ToValue(cv);
    }
}

Subtract the specified value.

e.g.

c = a.sub(b,n)
digits

If specified and less than the number of significant digits of the result, the result is rounded to that number of digits, according to ::mode.

to_d → bigdecimal Show source 
# File ext/bigdecimal/lib/bigdecimal/util.rb, line 108
def to_d
  self
end

Returns self.

require 'bigdecimal/util'

d = BigDecimal.new("3.14")
d.to_d                       # => 0.314e1
to_digits → string Show source 
# File ext/bigdecimal/lib/bigdecimal/util.rb, line 88
def to_digits
  if self.nan? || self.infinite? || self.zero?
    self.to_s
  else
    i       = self.to_i.to_s
    _,f,_,z = self.frac.split
    i + "." + ("0"*(-z)) + f
  end
end

Converts a BigDecimal to a String of the form “nnnnnn.mmm”. This method is deprecated; use #to_s(“F”) instead.

require 'bigdecimal/util'

d = BigDecimal.new("3.14")
d.to_digits                  # => "3.14"
to_f() Show source 
static VALUE
BigDecimal_to_f(VALUE self)
{
    ENTER(1);
    Real *p;
    double d;
    SIGNED_VALUE e;
    char *buf;
    volatile VALUE str;

    GUARD_OBJ(p, GetVpValue(self, 1));
    if (VpVtoD(&d, &e, p) != 1)
        return rb_float_new(d);
    if (e > (SIGNED_VALUE)(DBL_MAX_10_EXP+BASE_FIG))
        goto overflow;
    if (e < (SIGNED_VALUE)(DBL_MIN_10_EXP-BASE_FIG))
        goto underflow;

    str = rb_str_new(0, VpNumOfChars(p, "E"));
    buf = RSTRING_PTR(str);
    VpToString(p, buf, 0, 0);
    errno = 0;
    d = strtod(buf, 0);
    if (errno == ERANGE) {
        if (d == 0.0) goto underflow;
        if (fabs(d) >= HUGE_VAL) goto overflow;
    }
    return rb_float_new(d);

overflow:
    VpException(VP_EXCEPTION_OVERFLOW, "BigDecimal to Float conversion", 0);
    if (BIGDECIMAL_NEGATIVE_P(p))
        return rb_float_new(VpGetDoubleNegInf());
    else
        return rb_float_new(VpGetDoublePosInf());

underflow:
    VpException(VP_EXCEPTION_UNDERFLOW, "BigDecimal to Float conversion", 0);
    if (BIGDECIMAL_NEGATIVE_P(p))
        return rb_float_new(-0.0);
    else
        return rb_float_new(0.0);
}

Returns a new Float object having approximately the same value as the BigDecimal number. Normal accuracy limits and built-in errors of binary Float arithmetic apply.

to_i() Show source 
static VALUE
BigDecimal_to_i(VALUE self)
{
    ENTER(5);
    ssize_t e, nf;
    Real *p;

    GUARD_OBJ(p, GetVpValue(self, 1));
    BigDecimal_check_num(p);

    e = VpExponent10(p);
    if (e <= 0) return INT2FIX(0);
    nf = VpBaseFig();
    if (e <= nf) {
        return LONG2NUM((long)(VpGetSign(p) * (BDIGIT_DBL_SIGNED)p->frac[0]));
    }
    else {
        VALUE a = BigDecimal_split(self);
        VALUE digits = RARRAY_AREF(a, 1);
        VALUE numerator = rb_funcall(digits, rb_intern("to_i"), 0);
        VALUE ret;
        ssize_t dpower = e - (ssize_t)RSTRING_LEN(digits);

        if (BIGDECIMAL_NEGATIVE_P(p)) {
            numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
        }
        if (dpower < 0) {
            ret = rb_funcall(numerator, rb_intern("div"), 1,
                              rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                         INT2FIX(-dpower)));
        }
        else {
            ret = rb_funcall(numerator, '*', 1,
                             rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                        INT2FIX(dpower)));
        }
        if (RB_TYPE_P(ret, T_FLOAT)) {
            rb_raise(rb_eFloatDomainError, "Infinity");
        }
        return ret;
    }
}

Returns the value as an Integer.

If the BigDecimal is infinity or NaN, raises FloatDomainError.

to_int() Show source 
static VALUE
BigDecimal_to_i(VALUE self)
{
    ENTER(5);
    ssize_t e, nf;
    Real *p;

    GUARD_OBJ(p, GetVpValue(self, 1));
    BigDecimal_check_num(p);

    e = VpExponent10(p);
    if (e <= 0) return INT2FIX(0);
    nf = VpBaseFig();
    if (e <= nf) {
        return LONG2NUM((long)(VpGetSign(p) * (BDIGIT_DBL_SIGNED)p->frac[0]));
    }
    else {
        VALUE a = BigDecimal_split(self);
        VALUE digits = RARRAY_AREF(a, 1);
        VALUE numerator = rb_funcall(digits, rb_intern("to_i"), 0);
        VALUE ret;
        ssize_t dpower = e - (ssize_t)RSTRING_LEN(digits);

        if (BIGDECIMAL_NEGATIVE_P(p)) {
            numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
        }
        if (dpower < 0) {
            ret = rb_funcall(numerator, rb_intern("div"), 1,
                              rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                         INT2FIX(-dpower)));
        }
        else {
            ret = rb_funcall(numerator, '*', 1,
                             rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                        INT2FIX(dpower)));
        }
        if (RB_TYPE_P(ret, T_FLOAT)) {
            rb_raise(rb_eFloatDomainError, "Infinity");
        }
        return ret;
    }
}

Returns the value as an Integer.

If the BigDecimal is infinity or NaN, raises FloatDomainError.

to_json(*) Show source 
# File ext/json/lib/json/add/bigdecimal.rb, line 26
def to_json(*)
  as_json.to_json
end

return the JSON value

to_r() Show source 
static VALUE
BigDecimal_to_r(VALUE self)
{
    Real *p;
    ssize_t sign, power, denomi_power;
    VALUE a, digits, numerator;

    p = GetVpValue(self, 1);
    BigDecimal_check_num(p);

    sign = VpGetSign(p);
    power = VpExponent10(p);
    a = BigDecimal_split(self);
    digits = RARRAY_AREF(a, 1);
    denomi_power = power - RSTRING_LEN(digits);
    numerator = rb_funcall(digits, rb_intern("to_i"), 0);

    if (sign < 0) {
        numerator = rb_funcall(numerator, '*', 1, INT2FIX(-1));
    }
    if (denomi_power < 0) {
        return rb_Rational(numerator,
                           rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                      INT2FIX(-denomi_power)));
    }
    else {
        return rb_Rational1(rb_funcall(numerator, '*', 1,
                                       rb_funcall(INT2FIX(10), rb_intern("**"), 1,
                                                  INT2FIX(denomi_power))));
    }
}

Converts a BigDecimal to a Rational.

to_s(s) Show source 
static VALUE
BigDecimal_to_s(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    int   fmt = 0;   /* 0:E format */
    int   fPlus = 0; /* =0:default,=1: set ' ' before digits ,set '+' before digits. */
    Real  *vp;
    volatile VALUE str;
    char  *psz;
    char   ch;
    size_t nc, mc = 0;
    VALUE  f;

    GUARD_OBJ(vp, GetVpValue(self, 1));

    if (rb_scan_args(argc, argv, "01", &f) == 1) {
        if (RB_TYPE_P(f, T_STRING)) {
            psz = StringValueCStr(f);
            rb_check_safe_obj(f);
            if (*psz == ' ') {
                fPlus = 1;
                psz++;
            }
            else if (*psz == '+') {
                fPlus = 2;
                psz++;
            }
            while ((ch = *psz++) != 0) {
                if (ISSPACE(ch)) {
                    continue;
                }
                if (!ISDIGIT(ch)) {
                    if (ch == 'F' || ch == 'f') {
                        fmt = 1; /* F format */
                    }
                    break;
                }
                mc = mc*10 + ch - '0';
            }
        }
        else {
            mc = (size_t)GetPositiveInt(f);
        }
    }
    if (fmt) {
        nc = VpNumOfChars(vp, "F");
    }
    else {
        nc = VpNumOfChars(vp, "E");
    }
    if (mc > 0) {
        nc += (nc + mc - 1) / mc + 1;
    }

    str = rb_str_new(0, nc);
    psz = RSTRING_PTR(str);

    if (fmt) {
        VpToFString(vp, psz, mc, fPlus);
    }
    else {
        VpToString (vp, psz, mc, fPlus);
    }
    rb_str_resize(str, strlen(psz));
    return str;
}

Converts the value to a string.

The default format looks like 0.xxxxEnn.

The optional parameter s consists of either an integer; or an optional '+' or ' ', followed by an optional number, followed by an optional 'E' or 'F'.

If there is a '+' at the start of s, positive values are returned with a leading '+'.

A space at the start of s returns positive values with a leading space.

If s contains a number, a space is inserted after each group of that many fractional digits.

If s ends with an 'E', engineering notation (0.xxxxEnn) is used.

If s ends with an 'F', conventional floating point notation is used.

Examples:

BigDecimal.new('-123.45678901234567890').to_s('5F')
  #=> '-123.45678 90123 45678 9'

BigDecimal.new('123.45678901234567890').to_s('+8F')
  #=> '+123.45678901 23456789'

BigDecimal.new('123.45678901234567890').to_s(' F')
  #=> ' 123.4567890123456789'
truncate(n) Show source 
static VALUE
BigDecimal_truncate(int argc, VALUE *argv, VALUE self)
{
    ENTER(5);
    Real *c, *a;
    int iLoc;
    VALUE vLoc;
    size_t mx, pl = VpSetPrecLimit(0);

    if (rb_scan_args(argc, argv, "01", &vLoc) == 0) {
        iLoc = 0;
    }
    else {
        iLoc = NUM2INT(vLoc);
    }

    GUARD_OBJ(a, GetVpValue(self, 1));
    mx = a->Prec * (VpBaseFig() + 1);
    GUARD_OBJ(c, VpCreateRbObject(mx, "0"));
    VpSetPrecLimit(pl);
    VpActiveRound(c, a, VP_ROUND_DOWN, iLoc); /* 0: truncate */
    if (argc == 0) {
        return BigDecimal_to_i(ToValue(c));
    }
    return ToValue(c);
}

Truncate to the nearest integer (by default), returning the result as a BigDecimal.

BigDecimal('3.14159').truncate #=> 3
BigDecimal('8.7').truncate #=> 8
BigDecimal('-9.9').truncate #=> -9

If n is specified and positive, the fractional part of the result has no more than that many digits.

If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.

BigDecimal('3.14159').truncate(3) #=> 3.141
BigDecimal('13345.234').truncate(-2) #=> 13300.0
zero?() Show source 
static VALUE
BigDecimal_zero(VALUE self)
{
    Real *a = GetVpValue(self, 1);
    return VpIsZero(a) ? Qtrue : Qfalse;
}

Returns True if the value is zero.

Ruby Core © 1993–2017 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.