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Module: Math

Relationships & Source Files
Namespace Children
Exceptions:
DomainError
Defined in: math.c

Overview

The Math module contains module functions for basic trigonometric and transcendental functions. See class ::Float for a list of constants that define Ruby’s floating point accuracy.

Domains and codomains are given only for real (not complex) numbers.

Constant Summary

Class Method Summary

Class Method Details

.acos(x) ⇒ Float (mod_func)

Computes the arc cosine of x. Returns 0..PI.

Domain: [-1, 1]

Codomain: [0, PI]

Math.acos(0) == Math::PI/2  #=> true
[ GitHub ] 

  


# File 'math.c', line 178



static VALUE
math_acos(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_range(d, -1.0, 1.0, "acos");
    return DBL2NUM(acos(d));
}


  








  

    .acosh(x)  ⇒ Float  (mod_func)  



  

    

Computes the inverse hyperbolic cosine of x.



Domain: [1, INFINITY)



Codomain: [0, INFINITY)



Math.acosh(1) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 335



static VALUE
math_acosh(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_min(d, 1.0, "acosh");
    return DBL2NUM(acosh(d));
}


  








  

    .asin(x)  ⇒ Float  (mod_func)  



  

    

Computes the arc sine of x. Returns -PI/2..PI/2.



Domain: [-1, -1]



Codomain: [-PI/2, PI/2]



Math.asin(1) == Math::PI/2  #=> true


  



  [ GitHub ]


  

  


# File 'math.c', line 201



static VALUE
math_asin(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_range(d, -1.0, 1.0, "asin");
    return DBL2NUM(asin(d));
}


  








  

    .asinh(x)  ⇒ Float  (mod_func)  



  

    

Computes the inverse hyperbolic sine of x.



Domain: (-INFINITY, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.asinh(1) #=> 0.881373587019543


  



  [ GitHub ]


  

  


# File 'math.c', line 359



static VALUE
math_asinh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(asinh(Get_Double(x)));
}


  








  

    .atan(x)  ⇒ Float  (mod_func)  



  

    

Computes the arc tangent of x. Returns -PI/2..PI/2.



Domain: (-INFINITY, INFINITY)



Codomain: (-PI/2, PI/2)



Math.atan(0) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 224



static VALUE
math_atan(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(atan(Get_Double(x)));
}


  








  

    .atan2(y, x)  ⇒ Float  (mod_func)  



  

    

Computes the arc tangent given y and x. Returns a ::Float in the range -PI..PI. Return value is a angle in radians between the positive x-axis of cartesian plane and the point given by the coordinates (x, y) on it.



Domain: (-INFINITY, INFINITY)



Codomain: [-PI, PI]



Math.atan2(-0.0, -1.0) #=> -3.141592653589793
Math.atan2(-1.0, -1.0) #=> -2.356194490192345
Math.atan2(-1.0, 0.0)  #=> -1.5707963267948966
Math.atan2(-1.0, 1.0)  #=> -0.7853981633974483
Math.atan2(-0.0, 1.0)  #=> -0.0
Math.atan2(0.0, 1.0)   #=> 0.0
Math.atan2(1.0, 1.0)   #=> 0.7853981633974483
Math.atan2(1.0, 0.0)   #=> 1.5707963267948966
Math.atan2(1.0, -1.0)  #=> 2.356194490192345
Math.atan2(0.0, -1.0)  #=> 3.141592653589793
Math.atan2(INFINITY, INFINITY)   #=> 0.7853981633974483
Math.atan2(INFINITY, -INFINITY)  #=> 2.356194490192345
Math.atan2(-INFINITY, INFINITY)  #=> -0.7853981633974483
Math.atan2(-INFINITY, -INFINITY) #=> -2.356194490192345


  



  [ GitHub ]


  

  


# File 'math.c', line 71



static VALUE
math_atan2(VALUE unused_obj, VALUE y, VALUE x)
{
    double dx, dy;
    dx = Get_Double(x);
    dy = Get_Double(y);
    if (dx == 0.0 && dy == 0.0) {
	if (!signbit(dx))
	    return DBL2NUM(dy);
        if (!signbit(dy))
	    return DBL2NUM(M_PI);
	return DBL2NUM(-M_PI);
    }
#ifndef ATAN2_INF_C99
    if (isinf(dx) && isinf(dy)) {
	/* optimization for FLONUM */
	if (dx < 0.0) {
	    const double dz = (3.0 * M_PI / 4.0);
	    return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
	}
	else {
	    const double dz = (M_PI / 4.0);
	    return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
	}
    }
#endif
    return DBL2NUM(atan2(dy, dx));
}


  








  

    .atanh(x)  ⇒ Float  (mod_func)  



  

    

Computes the inverse hyperbolic tangent of x.



Domain: (-1, 1)



Codomain: (-INFINITY, INFINITY)



Math.atanh(1) #=> Infinity


  



  [ GitHub ]


  

  


# File 'math.c', line 379



static VALUE
math_atanh(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_range(d, -1.0, +1.0, "atanh");
    /* check for pole error */
    if (d == -1.0) return DBL2NUM(-HUGE_VAL);
    if (d == +1.0) return DBL2NUM(+HUGE_VAL);
    return DBL2NUM(atanh(d));
}


  








  

    .cbrt(x)  ⇒ Float  (mod_func)  



  

    

Returns the cube root of x.



Domain: (-INFINITY, INFINITY)



Codomain: (-INFINITY, INFINITY)



-9.upto(9) {|x|
  p [x, Math.cbrt(x), Math.cbrt(x)**3]
}
#=> [-9, -2.0800838230519, -9.0]
#   [-8, -2.0, -8.0]
#   [-7, -1.91293118277239, -7.0]
#   [-6, -1.81712059283214, -6.0]
#   [-5, -1.7099759466767, -5.0]
#   [-4, -1.5874010519682, -4.0]
#   [-3, -1.44224957030741, -3.0]
#   [-2, -1.25992104989487, -2.0]
#   [-1, -1.0, -1.0]
#   [0, 0.0, 0.0]
#   [1, 1.0, 1.0]
#   [2, 1.25992104989487, 2.0]
#   [3, 1.44224957030741, 3.0]
#   [4, 1.5874010519682, 4.0]
#   [5, 1.7099759466767, 5.0]
#   [6, 1.81712059283214, 6.0]
#   [7, 1.91293118277239, 7.0]
#   [8, 2.0, 8.0]
#   [9, 2.0800838230519, 9.0]


  



  [ GitHub ]


  

  


# File 'math.c', line 688



static VALUE
math_cbrt(VALUE unused_obj, VALUE x)
{
    double f = Get_Double(x);
    double r = cbrt(f);
#if defined __GLIBC__
    if (isfinite(r) && !(f == 0.0 && r == 0.0)) {
	r = (2.0 * r + (f / r / r)) / 3.0;
    }
#endif
    return DBL2NUM(r);
}


  








  

    .cos(x)  ⇒ Float  (mod_func)  



  

    

Computes the cosine of x (expressed in radians). Returns a ::Float in the range -1.0..1.0.



Domain: (-INFINITY, INFINITY)



Codomain: [-1, 1]



Math.cos(Math::PI) #=> -1.0


  



  [ GitHub ]


  

  


# File 'math.c', line 116



static VALUE
math_cos(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(cos(Get_Double(x)));
}


  








  

    .cosh(x)  ⇒ Float  (mod_func)  



  

    

Computes the hyperbolic cosine of x (expressed in radians).



Domain: (-INFINITY, INFINITY)



Codomain: [1, INFINITY)



Math.cosh(0) #=> 1.0


  



  [ GitHub ]


  

  


# File 'math.c', line 252



static VALUE
math_cosh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(cosh(Get_Double(x)));
}


  








  

    .erf(x)  ⇒ Float  (mod_func)  



  

    

Calculates the error function of x.



Domain: (-INFINITY, INFINITY)



Codomain: (-1, 1)



Math.erf(0) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 768



static VALUE
math_erf(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(erf(Get_Double(x)));
}


  








  

    .erfc(x)  ⇒ Float  (mod_func)  



  

    

Calculates the complementary error function of x.



Domain: (-INFINITY, INFINITY)



Codomain: (0, 2)



Math.erfc(0) #=> 1.0


  



  [ GitHub ]


  

  


# File 'math.c', line 788



static VALUE
math_erfc(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(erfc(Get_Double(x)));
}


  








  

    .exp(x)  ⇒ Float  (mod_func)  



  

    

Returns e**x.



Domain: (-INFINITY, INFINITY)



Codomain: (0, INFINITY)



Math.exp(0)       #=> 1.0
Math.exp(1)       #=> 2.718281828459045
Math.exp(1.5)     #=> 4.4816890703380645


  



  [ GitHub ]


  

  


# File 'math.c', line 408



static VALUE
math_exp(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(exp(Get_Double(x)));
}


  








  

    .frexp(x)  ⇒ Array, exponent  (mod_func)  



  

    

Returns a two-element array containing the normalized fraction (a ::Float) and exponent (an ::Integer) of x.



fraction, exponent = Math.frexp(1234)   #=> [0.6025390625, 11]
fraction * 2**exponent                  #=> 1234.0


  



  [ GitHub ]


  

  


# File 'math.c', line 712



static VALUE
math_frexp(VALUE unused_obj, VALUE x)
{
    double d;
    int exp;

    d = frexp(Get_Double(x), &exp);
    return rb_assoc_new(DBL2NUM(d), INT2NUM(exp));
}


  








  

    .gamma(x)  ⇒ Float  (mod_func)  



  

    

Calculates the gamma function of x.



Note that gamma(n) is the same as fact(n-1) for integer n > 0. However gamma(n) returns float and can be an approximation.



def fact(n) (1..n).inject(1) {|r,i| r*i } end
1.upto(26) {|i| p [i, Math.gamma(i), fact(i-1)] }
#=> [1, 1.0, 1]
#   [2, 1.0, 1]
#   [3, 2.0, 2]
#   [4, 6.0, 6]
#   [5, 24.0, 24]
#   [6, 120.0, 120]
#   [7, 720.0, 720]
#   [8, 5040.0, 5040]
#   [9, 40320.0, 40320]
#   [10, 362880.0, 362880]
#   [11, 3628800.0, 3628800]
#   [12, 39916800.0, 39916800]
#   [13, 479001600.0, 479001600]
#   [14, 6227020800.0, 6227020800]
#   [15, 87178291200.0, 87178291200]
#   [16, 1307674368000.0, 1307674368000]
#   [17, 20922789888000.0, 20922789888000]
#   [18, 355687428096000.0, 355687428096000]
#   [19, 6.402373705728e+15, 6402373705728000]
#   [20, 1.21645100408832e+17, 121645100408832000]
#   [21, 2.43290200817664e+18, 2432902008176640000]
#   [22, 5.109094217170944e+19, 51090942171709440000]
#   [23, 1.1240007277776077e+21, 1124000727777607680000]
#   [24, 2.5852016738885062e+22, 25852016738884976640000]
#   [25, 6.204484017332391e+23, 620448401733239439360000]
#   [26, 1.5511210043330954e+25, 15511210043330985984000000]


  



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# File 'math.c', line 834



static VALUE
math_gamma(VALUE unused_obj, VALUE x)
{
    static const double fact_table[] = {
        /* fact(0) */ 1.0,
        /* fact(1) */ 1.0,
        /* fact(2) */ 2.0,
        /* fact(3) */ 6.0,
        /* fact(4) */ 24.0,
        /* fact(5) */ 120.0,
        /* fact(6) */ 720.0,
        /* fact(7) */ 5040.0,
        /* fact(8) */ 40320.0,
        /* fact(9) */ 362880.0,
        /* fact(10) */ 3628800.0,
        /* fact(11) */ 39916800.0,
        /* fact(12) */ 479001600.0,
        /* fact(13) */ 6227020800.0,
        /* fact(14) */ 87178291200.0,
        /* fact(15) */ 1307674368000.0,
        /* fact(16) */ 20922789888000.0,
        /* fact(17) */ 355687428096000.0,
        /* fact(18) */ 6402373705728000.0,
        /* fact(19) */ 121645100408832000.0,
        /* fact(20) */ 2432902008176640000.0,
        /* fact(21) */ 51090942171709440000.0,
        /* fact(22) */ 1124000727777607680000.0,
        /* fact(23)=25852016738884976640000 needs 56bit mantissa which is
         * impossible to represent exactly in IEEE 754 double which have
         * 53bit mantissa. */
    };
    enum {NFACT_TABLE = numberof(fact_table)};
    double d;
    d = Get_Double(x);
    /* check for domain error */
    if (isinf(d)) {
	if (signbit(d)) domain_error("gamma");
	return DBL2NUM(HUGE_VAL);
    }
    if (d == 0.0) {
	return signbit(d) ? DBL2NUM(-HUGE_VAL) : DBL2NUM(HUGE_VAL);
    }
    if (d == floor(d)) {
	domain_check_min(d, 0.0, "gamma");
	if (1.0 <= d && d <= (double)NFACT_TABLE) {
	    return DBL2NUM(fact_table[(int)d - 1]);
	}
    }
    return DBL2NUM(tgamma(d));
}


  








  

    .hypot(x, y)  ⇒ Float  (mod_func)  



  

    

Returns sqrt(x**2 + y**2), the hypotenuse of a right-angled triangle with sides x and y.



Math.hypot(3, 4)   #=> 5.0


  



  [ GitHub ]


  

  


# File 'math.c', line 748



static VALUE
math_hypot(VALUE unused_obj, VALUE x, VALUE y)
{
    return DBL2NUM(hypot(Get_Double(x), Get_Double(y)));
}


  








  

    .ldexp(fraction, exponent)  ⇒ Float  (mod_func)  



  

    

Returns the value of fraction*(2**exponent).



fraction, exponent = Math.frexp(1234)
Math.ldexp(fraction, exponent)   #=> 1234.0


  



  [ GitHub ]


  

  


# File 'math.c', line 732



static VALUE
math_ldexp(VALUE unused_obj, VALUE x, VALUE n)
{
    return DBL2NUM(ldexp(Get_Double(x), NUM2INT(n)));
}


  








  

    .lgamma(x)  ⇒ Array, 1  (mod_func)  



  

    

Calculates the logarithmic gamma of x and the sign of gamma of x.



lgamma(x) is the same as



[Math.log(Math.gamma(x).abs), Math.gamma(x) < 0 ? -1 : 1]



but avoids overflow by .gamma(x) for large x.



Math.lgamma(0) #=> [Infinity, 1]


  



  [ GitHub ]


  

  


# File 'math.c', line 899



static VALUE
math_lgamma(VALUE unused_obj, VALUE x)
{
    double d;
    int sign=1;
    VALUE v;
    d = Get_Double(x);
    /* check for domain error */
    if (isinf(d)) {
	if (signbit(d)) domain_error("lgamma");
	return rb_assoc_new(DBL2NUM(HUGE_VAL), INT2FIX(1));
    }
    if (d == 0.0) {
	VALUE vsign = signbit(d) ? INT2FIX(-1) : INT2FIX(+1);
	return rb_assoc_new(DBL2NUM(HUGE_VAL), vsign);
    }
    v = DBL2NUM(lgamma_r(d, &sign));
    return rb_assoc_new(v, INT2FIX(sign));
}


  








  

    

      .log(x)  ⇒ Float  (mod_func)
      .log(x, base)  ⇒ Float 
    

  



  

    

Returns the logarithm of x. If additional second argument is given, it will be the base of logarithm. Otherwise it is e (for the natural logarithm).



Domain: (0, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.log(0)          #=> -Infinity
Math.log(1)          #=> 0.0
Math.log(Math::E)    #=> 1.0
Math.log(Math::E**3) #=> 3.0
Math.log(12, 3)      #=> 2.2618595071429146


  





  


  [ GitHub ]


  

  


# File 'math.c', line 454



static VALUE
math_log(int argc, const VALUE *argv, VALUE unused_obj)
{
    return rb_math_log(argc, argv);
}


  








  

    .log10(x)  ⇒ Float  (mod_func)  



  

    

Returns the base 10 logarithm of x.



Domain: (0, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.log10(1)       #=> 0.0
Math.log10(10)      #=> 1.0
Math.log10(10**100) #=> 100.0


  



  [ GitHub ]


  

  


# File 'math.c', line 562



static VALUE
math_log10(VALUE unused_obj, VALUE x)
{
    size_t numbits;
    double d = get_double_rshift(x, &numbits);

    domain_check_min(d, 0.0, "log10");
    /* check for pole error */
    if (d == 0.0) return DBL2NUM(-HUGE_VAL);

    return DBL2NUM(log10(d) + numbits * log10(2)); /* log10(d * 2 ** numbits) */
}


  








  

    .log2(x)  ⇒ Float  (mod_func)  



  

    

Returns the base 2 logarithm of x.



Domain: (0, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.log2(1)      #=> 0.0
Math.log2(2)      #=> 1.0
Math.log2(32768)  #=> 15.0
Math.log2(65536)  #=> 16.0


  



  [ GitHub ]


  

  


# File 'math.c', line 533



static VALUE
math_log2(VALUE unused_obj, VALUE x)
{
    size_t numbits;
    double d = get_double_rshift(x, &numbits);

    domain_check_min(d, 0.0, "log2");
    /* check for pole error */
    if (d == 0.0) return DBL2NUM(-HUGE_VAL);

    return DBL2NUM(log2(d) + numbits); /* log2(d * 2 ** numbits) */
}


  








  

    .sin(x)  ⇒ Float  (mod_func)  



  

    

Computes the sine of x (expressed in radians). Returns a ::Float in the range -1.0..1.0.



Domain: (-INFINITY, INFINITY)



Codomain: [-1, 1]



Math.sin(Math::PI/2) #=> 1.0


  



  [ GitHub ]


  

  


# File 'math.c', line 137



static VALUE
math_sin(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(sin(Get_Double(x)));
}


  








  

    .sinh(x)  ⇒ Float  (mod_func)  



  

    

Computes the hyperbolic sine of x (expressed in radians).



Domain: (-INFINITY, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.sinh(0) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 280



static VALUE
math_sinh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(sinh(Get_Double(x)));
}


  








  

    .sqrt(x)  ⇒ Float  (mod_func)  



  

    

Returns the non-negative square root of x.



Domain: [0, INFINITY)



Codomain:[0, INFINITY)



0.upto(10) {|x|
  p [x, Math.sqrt(x), Math.sqrt(x)**2]
}
#=> [0, 0.0, 0.0]
#   [1, 1.0, 1.0]
#   [2, 1.4142135623731, 2.0]
#   [3, 1.73205080756888, 3.0]
#   [4, 2.0, 4.0]
#   [5, 2.23606797749979, 5.0]
#   [6, 2.44948974278318, 6.0]
#   [7, 2.64575131106459, 7.0]
#   [8, 2.82842712474619, 8.0]
#   [9, 3.0, 9.0]
#   [10, 3.16227766016838, 10.0]



Note that the limited precision of floating point arithmetic might lead to surprising results:



Math.sqrt(10**46).to_i  #=> 99999999999999991611392 (!)



See also BigDecimal#sqrt and Integer.sqrt.


  



  [ GitHub ]


  

  


# File 'math.c', line 610



static VALUE
math_sqrt(VALUE unused_obj, VALUE x)
{
    return rb_math_sqrt(x);
}


  








  

    .tan(x)  ⇒ Float  (mod_func)  



  

    

Computes the tangent of x (expressed in radians).



Domain: (-INFINITY, INFINITY)



Codomain: (-INFINITY, INFINITY)



Math.tan(0) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 158



static VALUE
math_tan(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(tan(Get_Double(x)));
}


  








  

    .tanh(x)  ⇒ Float  (mod_func)  



  

    

Computes the hyperbolic tangent of x (expressed in radians).



Domain: (-INFINITY, INFINITY)



Codomain: (-1, 1)



Math.tanh(0) #=> 0.0


  



  [ GitHub ]


  

  


# File 'math.c', line 315



static VALUE
math_tanh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(tanh(Get_Double(x)));
}