From 69c1145fa8832e9ba23bcd66a2552964bcb6085a Mon Sep 17 00:00:00 2001 From: Burdette Lamar Date: Mon, 25 Apr 2022 10:07:21 -0500 Subject: [DOC] Enhanced RDoc for Math module (#5837) Revises intro. Adds "What's Here". Revises methods doc. --- doc/math/math.rdoc | 117 +++++++++++ math.c | 582 +++++++++++++++++++++++++++++++---------------------- 2 files changed, 457 insertions(+), 242 deletions(-) create mode 100644 doc/math/math.rdoc diff --git a/doc/math/math.rdoc b/doc/math/math.rdoc new file mode 100644 index 0000000000..7a89df951c --- /dev/null +++ b/doc/math/math.rdoc @@ -0,0 +1,117 @@ +\Module \Math provides methods for basic trigonometric, +logarithmic, and transcendental functions, and for extracting roots. + +You can write its constants and method calls thus: + + Math::PI # => 3.141592653589793 + Math::E # => 2.718281828459045 + Math.sin(0.0) # => 0.0 + Math.cos(0.0) # => 1.0 + +If you include module \Math, you can write simpler forms: + + include Math + PI # => 3.141592653589793 + E # => 2.718281828459045 + sin(0.0) # => 0.0 + cos(0.0) # => 1.0 + +For simplicity, the examples here assume: + + include Math + INFINITY = Float::INFINITY + +The domains and ranges for the methods +are denoted by open or closed intervals, +using, respectively, parentheses or square brackets: + +- An open interval does not include the endpoints: + + (-INFINITY, INFINITY) + +- A closed interval includes the endpoints: + + [-1.0, 1.0] + +- A half-open interval includes one endpoint, but not the other: + + [1.0, INFINITY) + +Many values returned by \Math methods are numerical approximations. +This is because many such values are, in mathematics, +of infinite precision, while in numerical computation +the precision is finite. + +Thus, in mathematics, cos(π/2) is exactly zero, +but in our computation cos(PI/2) is a number very close to zero: + + cos(PI/2) # => 6.123031769111886e-17 + +For very large and very small returned values, +we have added formatted numbers for clarity: + + tan(PI/2) # => 1.633123935319537e+16 # 16331239353195370.0 + tan(PI) # => -1.2246467991473532e-16 # -0.0000000000000001 + +See class Float for the constants +that affect Ruby's floating-point arithmetic. + +=== What's Here + +==== Trigonometric Functions + +- ::cos: Returns the cosine of the given argument. +- ::sin: Returns the sine of the given argument. +- ::tan: Returns the tangent of the given argument. + +==== Inverse Trigonometric Functions + +- ::acos: Returns the arc cosine of the given argument. +- ::asin: Returns the arc sine of the given argument. +- ::atan: Returns the arc tangent of the given argument. +- ::atan2: Returns the arg tangent of two given arguments. + +==== Hyperbolic Trigonometric Functions + +- ::cosh: Returns the hyperbolic cosine of the given argument. +- ::sinh: Returns the hyperbolic sine of the given argument. +- ::tanh: Returns the hyperbolic tangent of the given argument. + +==== Inverse Hyperbolic Trigonometric Functions + +- ::acosh: Returns the inverse hyperbolic cosine of the given argument. +- ::asinh: Returns the inverse hyperbolic sine of the given argument. +- ::atanh: Returns the inverse hyperbolic tangent of the given argument. + +==== Exponentiation and Logarithmic Functions + +- ::exp: Returns the value of a given value raised to a given power. +- ::log: Returns the logarithm of a given value in a given base. +- ::log10: Returns the base 10 logarithm of the given argument. +- ::log2: Returns the base 2 logarithm of the given argument. + +==== Fraction and Exponent Functions + +- ::frexp: Returns the fraction and exponent of the given argument. +- ::ldexp: Returns the value for a given fraction and exponent. + +==== Root Functions + +- ::cbrt: Returns the cube root of the given argument. +- ::sqrt: Returns the square root of the given argument. + +==== Error Functions + +- ::erf: Returns the value of the Gauss error function for the given argument. +- ::erfc: Returns the value of the complementary error function + for the given argument. + +==== Gamma Functions + +- ::gamma: Returns the value of the gamma function for the given argument. +- ::lgamma: Returns the value of the logarithmic gamma function + for the given argument. + +==== Hypotenuse Function + +- ::hypot: Returns sqrt(a**2 + b**2) for the given +a+ and +b+. diff --git a/math.c b/math.c index cce29b526b..4996718b10 100644 --- a/math.c +++ b/math.c @@ -40,31 +40,21 @@ VALUE rb_eMathDomainError; /* * call-seq: - * Math.atan2(y, x) -> Float - * - * 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 + * Math.atan2(y, x) -> float + * + * Returns the {arc tangent}[https://en.wikipedia.org/wiki/Atan2] of +y+ and +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. + * + * - Domain of +y+: [-INFINITY, INFINITY]. + * - Domain of +x+: [-INFINITY, INFINITY]. + * - Range: [-PI, PI]. + * + * Examples: + * + * atan2(-1.0, -1.0) # => -2.356194490192345 # -3*PI/4 + * atan2(-1.0, 0.0) # => -1.5707963267948966 # -PI/2 + * atan2(-1.0, 1.0) # => -0.7853981633974483 # -PI/4 + * atan2(0.0, -1.0) # => 3.141592653589793 # PI * */ @@ -100,16 +90,22 @@ math_atan2(VALUE unused_obj, VALUE y, VALUE x) /* * call-seq: - * Math.cos(x) -> Float + * Math.cos(x) -> float * - * Computes the cosine of +x+ (expressed in radians). - * Returns a Float in the range -1.0..1.0. + * Returns the + * {cosine}[https://en.wikipedia.org/wiki/Sine_and_cosine] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: (-INFINITY, INFINITY). + * - Range: [-1.0, 1.0]. * - * Codomain: [-1, 1] + * Examples: * - * Math.cos(Math::PI) #=> -1.0 + * cos(-PI) # => -1.0 + * cos(-PI/2) # => 6.123031769111886e-17 # 0.0000000000000001 + * cos(0.0) # => 1.0 + * cos(PI/2) # => 6.123031769111886e-17 # 0.0000000000000001 + * cos(PI) # => -1.0 * */ @@ -121,16 +117,22 @@ math_cos(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.sin(x) -> Float + * Math.sin(x) -> float * - * Computes the sine of +x+ (expressed in radians). - * Returns a Float in the range -1.0..1.0. + * Returns the + * {sine}[https://en.wikipedia.org/wiki/Sine_and_cosine] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: (-INFINITY, INFINITY). + * - Range: [-1.0, 1.0]. * - * Codomain: [-1, 1] + * Examples: * - * Math.sin(Math::PI/2) #=> 1.0 + * sin(-PI) # => -1.2246063538223773e-16 # -0.0000000000000001 + * sin(-PI/2) # => -1.0 + * sin(0.0) # => 0.0 + * sin(PI/2) # => 1.0 + * sin(PI) # => 1.2246063538223773e-16 # 0.0000000000000001 * */ @@ -143,15 +145,22 @@ math_sin(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.tan(x) -> Float + * Math.tan(x) -> float * - * Computes the tangent of +x+ (expressed in radians). + * Returns the + * {tangent}[https://en.wikipedia.org/wiki/Trigonometric_functions] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: (-INFINITY, INFINITY). + * - Range: (-INFINITY, INFINITY). * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.tan(0) #=> 0.0 + * tan(-PI) # => 1.2246467991473532e-16 # -0.0000000000000001 + * tan(-PI/2) # => -1.633123935319537e+16 # -16331239353195370.0 + * tan(0.0) # => 0.0 + * tan(PI/2) # => 1.633123935319537e+16 # 16331239353195370.0 + * tan(PI) # => -1.2246467991473532e-16 # -0.0000000000000001 * */ @@ -163,15 +172,18 @@ math_tan(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.acos(x) -> Float + * Math.acos(x) -> float * - * Computes the arc cosine of +x+. Returns 0..PI. + * Returns the {arc cosine}[https://en.wikipedia.org/wiki/Inverse_trigonometric_functions] of +x+. * - * Domain: [-1, 1] + * - Domain: [-1, 1]. + * - Range: [0, PI]. * - * Codomain: [0, PI] + * Examples: * - * Math.acos(0) == Math::PI/2 #=> true + * acos(-1.0) # => 3.141592653589793 # PI + * acos(0.0) # => 1.5707963267948966 # PI/2 + * acos(1.0) # => 0.0 * */ @@ -187,15 +199,19 @@ math_acos(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.asin(x) -> Float + * Math.asin(x) -> float + * + * Returns the {arc sine}[https://en.wikipedia.org/wiki/Inverse_trigonometric_functions] of +x+. * - * Computes the arc sine of +x+. Returns -PI/2..PI/2. + * - Domain: [-1, -1]. + * - Range: [-PI/2, PI/2]. * - * Domain: [-1, -1] + * Examples: * - * Codomain: [-PI/2, PI/2] + * asin(-1.0) # => -1.5707963267948966 # -PI/2 + * asin(0.0) # => 0.0 + * asin(1.0) # => 1.5707963267948966 # PI/2 * - * Math.asin(1) == Math::PI/2 #=> true */ static VALUE @@ -212,13 +228,21 @@ math_asin(VALUE unused_obj, VALUE x) * call-seq: * Math.atan(x) -> Float * - * Computes the arc tangent of +x+. Returns -PI/2..PI/2. + * Returns the {arc tangent}[https://en.wikipedia.org/wiki/Inverse_trigonometric_functions] of +x+. + * + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-PI/2, PI/2] . * - * Domain: (-INFINITY, INFINITY) + * Examples: * - * Codomain: (-PI/2, PI/2) + * atan(-INFINITY) # => -1.5707963267948966 # -PI2 + * atan(-PI) # => -1.2626272556789115 + * atan(-PI/2) # => -1.0038848218538872 + * atan(0.0) # => 0.0 + * atan(PI/2) # => 1.0038848218538872 + * atan(PI) # => 1.2626272556789115 + * atan(INFINITY) # => 1.5707963267948966 # PI/2 * - * Math.atan(0) #=> 0.0 */ static VALUE @@ -237,15 +261,19 @@ cosh(double x) /* * call-seq: - * Math.cosh(x) -> Float + * Math.cosh(x) -> float * - * Computes the hyperbolic cosine of +x+ (expressed in radians). + * Returns the {hyperbolic cosine}[https://en.wikipedia.org/wiki/Hyperbolic_functions] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [1, INFINITY]. * - * Codomain: [1, INFINITY) + * Examples: * - * Math.cosh(0) #=> 1.0 + * cosh(-INFINITY) # => Infinity + * cosh(0.0) # => 1.0 + * cosh(INFINITY) # => Infinity * */ @@ -265,15 +293,19 @@ sinh(double x) /* * call-seq: - * Math.sinh(x) -> Float + * Math.sinh(x) -> float * - * Computes the hyperbolic sine of +x+ (expressed in radians). + * Returns the {hyperbolic sine}[https://en.wikipedia.org/wiki/Hyperbolic_functions] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-INFINITY, INFINITY]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.sinh(0) #=> 0.0 + * sinh(-INFINITY) # => -Infinity + * sinh(0.0) # => 0.0 + * sinh(INFINITY) # => Infinity * */ @@ -300,15 +332,19 @@ tanh(double x) /* * call-seq: - * Math.tanh(x) -> Float + * Math.tanh(x) -> float * - * Computes the hyperbolic tangent of +x+ (expressed in radians). + * Returns the {hyperbolic tangent}[https://en.wikipedia.org/wiki/Hyperbolic_functions] of +x+ + * in {radians}[https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus_degrees]. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-1, 1]. * - * Codomain: (-1, 1) + * Examples: * - * Math.tanh(0) #=> 0.0 + * tanh(-INFINITY) # => -1.0 + * tanh(0.0) # => 0.0 + * tanh(INFINITY) # => 1.0 * */ @@ -320,15 +356,17 @@ math_tanh(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.acosh(x) -> Float + * Math.acosh(x) -> float * - * Computes the inverse hyperbolic cosine of +x+. + * Returns the {inverse hyperbolic cosine}[https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions] of +x+. * - * Domain: [1, INFINITY) + * - Domain: [1, INFINITY]. + * - Range: [0, INFINITY]. * - * Codomain: [0, INFINITY) + * Examples: * - * Math.acosh(1) #=> 0.0 + * acosh(1.0) # => 0.0 + * acosh(INFINITY) # => Infinity * */ @@ -344,15 +382,18 @@ math_acosh(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.asinh(x) -> Float + * Math.asinh(x) -> float * - * Computes the inverse hyperbolic sine of +x+. + * Returns the {inverse hyperbolic sine}[https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions] of +x+. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-INFINITY, INFINITY]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.asinh(1) #=> 0.881373587019543 + * asinh(-INFINITY) # => -Infinity + * asinh(0.0) # => 0.0 + * asinh(INFINITY) # => Infinity * */ @@ -364,15 +405,18 @@ math_asinh(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.atanh(x) -> Float + * Math.atanh(x) -> float * - * Computes the inverse hyperbolic tangent of +x+. + * Returns the {inverse hyperbolic tangent}[https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions] of +x+. * - * Domain: (-1, 1) + * - Domain: [-1, 1]. + * - Range: [-INFINITY, INFINITY]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.atanh(1) #=> Infinity + * atanh(-1.0) # => -Infinity + * atanh(0.0) # => 0.0 + * atanh(1.0) # => Infinity * */ @@ -391,17 +435,22 @@ math_atanh(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.exp(x) -> Float + * Math.exp(x) -> float * - * Returns e**x. + * Returns +e+ raised to the +x+ power. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [0, INFINITY]. * - * Codomain: (0, INFINITY) + * Examples: * - * Math.exp(0) #=> 1.0 - * Math.exp(1) #=> 2.718281828459045 - * Math.exp(1.5) #=> 4.4816890703380645 + * exp(-INFINITY) # => 0.0 + * exp(-1.0) # => 0.36787944117144233 # 1.0/E + * exp(0.0) # => 1.0 + * exp(0.5) # => 1.6487212707001282 # sqrt(E) + * exp(1.0) # => 2.718281828459045 # E + * exp(2.0) # => 7.38905609893065 # E**2 + * exp(INFINITY) # => Infinity * */ @@ -432,22 +481,27 @@ FUNC_MINIMIZED(static VALUE math_log(int, const VALUE *, VALUE)); /* * call-seq: - * Math.log(x) -> Float - * Math.log(x, base) -> Float + * Math.log(x, base = Math::E) -> 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). + * Returns the base +base+ {logarithm}[https://en.wikipedia.org/wiki/Logarithm] of +x+. * - * Domain: (0, INFINITY) + * - Domain: [0, INFINITY]. + * - Range: [-INFINITY, INFINITY)]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * 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 + * log(0.0) # => -Infinity + * log(1.0) # => 0.0 + * log(E) # => 1.0 + * log(INFINITY) # => Infinity + * + * log(0.0, 2.0) # => -Infinity + * log(1.0, 2.0) # => 0.0 + * log(2.0, 2.0) # => 1.0 + * + * log(0.0, 10.0) # => -Infinity + * log(1.0, 10.0) # => 0.0 + * log(10.0, 10.0) # => 1.0 * */ @@ -515,18 +569,19 @@ extern double log2(double); /* * call-seq: - * Math.log2(x) -> Float + * Math.log2(x) -> float * - * Returns the base 2 logarithm of +x+. + * Returns the base 2 {logarithm}[https://en.wikipedia.org/wiki/Logarithm] of +x+. * - * Domain: (0, INFINITY) + * - Domain: [0, INFINITY]. + * - Range: [-INFINITY, INFINITY]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.log2(1) #=> 0.0 - * Math.log2(2) #=> 1.0 - * Math.log2(32768) #=> 15.0 - * Math.log2(65536) #=> 16.0 + * log2(0.0) # => -Infinity + * log2(1.0) # => 0.0 + * log2(2.0) # => 1.0 + * log2(INFINITY) # => Infinity * */ @@ -545,17 +600,19 @@ math_log2(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.log10(x) -> Float + * Math.log10(x) -> float * - * Returns the base 10 logarithm of +x+. + * Returns the base 10 {logarithm}[https://en.wikipedia.org/wiki/Logarithm] of +x+. * - * Domain: (0, INFINITY) + * - Domain: [0, INFINITY]. + * - Range: [-INFINITY, INFINITY]. * - * Codomain: (-INFINITY, INFINITY) + * Examples: * - * Math.log10(1) #=> 0.0 - * Math.log10(10) #=> 1.0 - * Math.log10(10**100) #=> 100.0 + * log10(0.0) # => -Infinity + * log10(1.0) # => 0.0 + * log10(10.0) # => 1.0 + * log10(INFINITY) # => Infinity * */ @@ -576,35 +633,23 @@ static VALUE rb_math_sqrt(VALUE x); /* * call-seq: - * Math.sqrt(x) -> Float - * - * Returns the non-negative square root of +x+. + * Math.sqrt(x) -> float * - * Domain: [0, INFINITY) + * Returns the principal (non-negative) {square root}[https://en.wikipedia.org/wiki/Square_root] of +x+. * - * Codomain:[0, INFINITY) + * - Domain: [0, INFINITY]. + * - Range: [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] + * Examples: * - * Note that the limited precision of floating point arithmetic - * might lead to surprising results: + * sqrt(0.0) # => 0.0 + * sqrt(0.5) # => 0.7071067811865476 + * sqrt(1.0) # => 1.0 + * sqrt(2.0) # => 1.4142135623730951 + * sqrt(4.0) # => 2.0 + * sqrt(9.0) # => 3.0 + * sqrt(INFINITY) # => Infinity * - * Math.sqrt(10**46).to_i #=> 99999999999999991611392 (!) - * - * See also BigDecimal#sqrt and Integer.sqrt. */ static VALUE @@ -652,36 +697,26 @@ rb_math_sqrt(VALUE x) /* * call-seq: - * Math.cbrt(x) -> Float - * - * 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] + * Math.cbrt(x) -> float + * + * Returns the {cube root}[https://en.wikipedia.org/wiki/Cube_root] of +x+. + * + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-INFINITY, INFINITY]. + * + * Examples: + * + * cbrt(-INFINITY) # => -Infinity + * cbrt(-27.0) # => -3.0 + * cbrt(-8.0) # => -2.0 + * cbrt(-2.0) # => -1.2599210498948732 + * cbrt(1.0) # => 1.0 + * cbrt(0.0) # => 0.0 + * cbrt(1.0) # => 1.0 + cbrt(2.0) # => 1.2599210498948732 + * cbrt(8.0) # => 2.0 + * cbrt(27.0) # => 3.0 + * cbrt(INFINITY) # => Infinity * */ @@ -700,13 +735,30 @@ math_cbrt(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.frexp(x) -> [fraction, exponent] + * Math.frexp(x) -> [fraction, exponent] + * + * Returns a 2-element array containing the normalized signed float +fraction+ + * and integer +exponent+ of +x+ such that: + * + * x = fraction * 2**exponent * - * Returns a two-element array containing the normalized fraction (a Float) - * and exponent (an Integer) of +x+. + * See {IEEE 754 double-precision binary floating-point format: binary64}[https://en.wikipedia.org/wiki/Double-precision_floating-point_format#IEEE_754_double-precision_binary_floating-point_format:_binary64]. + * + * - Domain: [-INFINITY, INFINITY]. + * - Range [-INFINITY, INFINITY]. + * + * Examples: + * + * frexp(-INFINITY) # => [-Infinity, -1] + * frexp(-2.0) # => [-0.5, 2] + * frexp(-1.0) # => [-0.5, 1] + * frexp(0.0) # => [0.0, 0] + * frexp(1.0) # => [0.5, 1] + * frexp(2.0) # => [0.5, 2] + * frexp(INFINITY) # => [Infinity, -1] + * + * Related: Math.ldexp (inverse of Math.frexp). * - * fraction, exponent = Math.frexp(1234) #=> [0.6025390625, 11] - * fraction * 2**exponent #=> 1234.0 */ static VALUE @@ -721,12 +773,28 @@ math_frexp(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.ldexp(fraction, exponent) -> float + * Math.ldexp(fraction, exponent) -> float + * + * Returns the value of fraction * 2**exponent. * - * Returns the value of +fraction+*(2**+exponent+). + * - Domain of +fraction+: [0.0, 1.0). + * - Domain of +exponent+: [0, 1024] + * (larger values are equivalent to 1024). + * + * See {IEEE 754 double-precision binary floating-point format: binary64}[https://en.wikipedia.org/wiki/Double-precision_floating-point_format#IEEE_754_double-precision_binary_floating-point_format:_binary64]. + * + * Examples: + * + * ldexp(-INFINITY, -1) # => -Infinity + * ldexp(-0.5, 2) # => -2.0 + * ldexp(-0.5, 1) # => -1.0 + * ldexp(0.0, 0) # => 0.0 + * ldexp(-0.5, 1) # => 1.0 + * ldexp(-0.5, 2) # => 2.0 + * ldexp(INFINITY, -1) # => Infinity + * + * Related: Math.frexp (inverse of Math.ldexp). * - * fraction, exponent = Math.frexp(1234) - * Math.ldexp(fraction, exponent) #=> 1234.0 */ static VALUE @@ -737,12 +805,27 @@ math_ldexp(VALUE unused_obj, VALUE x, VALUE n) /* * call-seq: - * Math.hypot(x, y) -> Float + * Math.hypot(a, b) -> float + * + * Returns sqrt(a**2 + b**2), + * which is the length of the longest side +c+ (the hypotenuse) + * of the right triangle whose other sides have lengths +a+ and +b+. + * + * - Domain of +a+: [-INFINITY, INFINITY]. + * - Domain of +ab: [-INFINITY, INFINITY]. + * - Range: [0, INFINITY]. * - * Returns sqrt(x**2 + y**2), the hypotenuse of a right-angled triangle with - * sides +x+ and +y+. + * Examples: + * + * hypot(0.0, 1.0) # => 1.0 + * hypot(1.0, 1.0) # => 1.4142135623730951 # sqrt(2.0) + * hypot(3.0, 4.0) # => 5.0 + * hypot(5.0, 12.0) # => 13.0 + * hypot(1.0, sqrt(3.0)) # => 1.9999999999999998 # Near 2.0 + * + * Note that if either argument is +INFINITY+ or -INFINITY, + * the result is +Infinity+. * - * Math.hypot(3, 4) #=> 5.0 */ static VALUE @@ -753,15 +836,20 @@ math_hypot(VALUE unused_obj, VALUE x, VALUE y) /* * call-seq: - * Math.erf(x) -> Float + * Math.erf(x) -> float + * + * Returns the value of the {Gauss error function}[https://en.wikipedia.org/wiki/Error_function] for +x+. * - * Calculates the error function of +x+. + * - Domain: [-INFINITY, INFINITY]. + * - Range: [-1, 1]. * - * Domain: (-INFINITY, INFINITY) + * Examples: * - * Codomain: (-1, 1) + * erf(-INFINITY) # => -1.0 + * erf(0.0) # => 0.0 + * erf(INFINITY) # => 1.0 * - * Math.erf(0) #=> 0.0 + * Related: Math.erfc. * */ @@ -775,13 +863,18 @@ math_erf(VALUE unused_obj, VALUE x) * call-seq: * Math.erfc(x) -> Float * - * Calculates the complementary error function of x. + * Returns the value of the {complementary error function}[https://en.wikipedia.org/wiki/Error_function#Complementary_error_function] for +x+. * - * Domain: (-INFINITY, INFINITY) + * - Domain: [-INFINITY, INFINITY]. + * - Range: [0, 2]. * - * Codomain: (0, 2) + * Examples: * - * Math.erfc(0) #=> 1.0 + * erfc(-INFINITY) # => 2.0 + * erfc(0.0) # => 1.0 + * erfc(INFINITY) # => 0.0 + * + * Related: Math.erf. * */ @@ -793,41 +886,26 @@ math_erfc(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.gamma(x) -> Float - * - * 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] + * Math.gamma(x) -> float + * + * Returns the value of the {gamma function}[https://en.wikipedia.org/wiki/Gamma_function] for +x+. + * + * - Domain: (-INFINITY, INFINITY] excluding negative integers. + * - Range: [-INFINITY, INFINITY]. + * + * Examples: + * + * gamma(-2.5) # => -0.9453087204829431 + * gamma(-1.5) # => 2.3632718012073513 + * gamma(-0.5) # => -3.5449077018110375 + * gamma(0.0) # => Infinity + * gamma(1.0) # => 1.0 + * gamma(2.0) # => 1.0 + * gamma(3.0) # => 2.0 + * gamma(4.0) # => 6.0 + * gamma(5.0) # => 24.0 + * + * Related: Math.lgamma. * */ @@ -884,15 +962,39 @@ math_gamma(VALUE unused_obj, VALUE x) /* * call-seq: - * Math.lgamma(x) -> [float, -1 or 1] + * Math.lgamma(x) -> [float, -1 or 1] + * + * Returns a 2-element array equivalent to: + * + * [Math.log(Math.gamma(x).abs), Math.gamma(x) < 0 ? -1 : 1] + * + * See {logarithmic gamma function}[https://en.wikipedia.org/wiki/Gamma_function#The_log-gamma_function]. + * + * - Domain: (-INFINITY, INFINITY]. + * - Range of first element: (-INFINITY, INFINITY]. + * - Second element is -1 or 1. + * + * Examples: + * + * lgamma(-4.0) # => [Infinity, -1] + * lgamma(-3.0) # => [Infinity, -1] + * lgamma(-2.0) # => [Infinity, -1] + * lgamma(-1.0) # => [Infinity, -1] + * lgamma(0.0) # => [Infinity, 1] * - * Calculates the logarithmic gamma of +x+ and the sign of gamma of +x+. + * lgamma(1.0) # => [0.0, 1] + * lgamma(2.0) # => [0.0, 1] + * lgamma(3.0) # => [0.6931471805599436, 1] + * lgamma(4.0) # => [1.7917594692280545, 1] * - * Math.lgamma(x) is the same as - * [Math.log(Math.gamma(x).abs), Math.gamma(x) < 0 ? -1 : 1] - * but avoids overflow by Math.gamma(x) for large x. + * lgamma(-2.5) # => [-0.05624371649767279, -1] + * lgamma(-1.5) # => [0.8600470153764797, 1] + * lgamma(-0.5) # => [1.265512123484647, -1] + * lgamma(0.5) # => [0.5723649429247004, 1] + * lgamma(1.5) # => [-0.12078223763524676, 1] + * lgamma(2.5) # => [0.2846828704729205, 1] * - * Math.lgamma(0) #=> [Infinity, 1] + * Related: Math.gamma. * */ @@ -962,12 +1064,8 @@ exp1(sqrt) /* * Document-class: Math * - * 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. + * :include: doc/math/math.rdoc * - * Domains and codomains are given only for real (not complex) numbers. */ -- cgit v1.2.3