module BigMath
Core BigMath methods for BigDecimal (log, exp) are defined here. Other methods (sin, cos, atan) are defined in ‘bigdecimal/math.rb’.
Provides mathematical functions.
Example:
require "bigdecimal/math" include BigMath a = BigDecimal((PI(49)/2).to_s) puts sin(a,100) # => 0.9999999999...9999999986e0
Public Instance Methods
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 944 def E(prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :E) exp(1, prec) end
Computes e (the base of natural logarithms) to the specified number of digits of precision, numeric.
BigMath.E(32).to_s #=> "0.27182818284590452353602874713527e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 899 def PI(prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :PI) n = prec + BigDecimal.double_fig zero = BigDecimal("0") one = BigDecimal("1") two = BigDecimal("2") m25 = BigDecimal("-0.04") m57121 = BigDecimal("-57121") pi = zero d = one k = one t = BigDecimal("-80") while d.nonzero? && ((m = n - (pi.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig t = t*m25 d = t.div(k,m) k = k+two pi = pi + d end d = one k = one t = BigDecimal("956") while d.nonzero? && ((m = n - (pi.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig t = t.div(m57121,n) d = t.div(k,m) pi = pi + d k = k+two end pi.mult(1, prec) end
Computes the value of pi to the specified number of digits of precision, numeric.
BigMath.PI(32).to_s #=> "0.31415926535897932384626433832795e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 256 def acos(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :acos) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :acos) raise Math::DomainError, "Out of domain argument for acos" if x < -1 || x > 1 return BigDecimal::Internal.nan_computation_result if x.nan? prec2 = prec + BigDecimal.double_fig return (PI(prec2) / 2).sub(asin(x, prec2), prec) if x < 0 return PI(prec2).div(2, prec) if x.zero? sin = (1 - x**2).sqrt(prec2) atan(sin.div(x, prec2), prec) end
Computes the arccosine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.acos(BigDecimal('0.5'), 32).to_s #=> "0.10471975511965977461542144610932e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 446 def acosh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :acosh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :acosh) raise Math::DomainError, "Out of domain argument for acosh" if x < 1 return BigDecimal::Internal.infinity_computation_result if x.infinite? return BigDecimal::Internal.nan_computation_result if x.nan? log(x + sqrt(x**2 - 1, prec + BigDecimal.double_fig), prec) end
Computes the inverse hyperbolic cosine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.acosh(BigDecimal('2'), 32).to_s #=> "0.1316957896924816708625046347308e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 230 def asin(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :asin) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :asin) raise Math::DomainError, "Out of domain argument for asin" if x < -1 || x > 1 return BigDecimal::Internal.nan_computation_result if x.nan? prec2 = prec + BigDecimal.double_fig cos = (1 - x**2).sqrt(prec2) if cos.zero? PI(prec2).div(x > 0 ? 2 : -2, prec) else atan(x.div(cos, prec2), prec) end end
Computes the arcsine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.asin(BigDecimal('0.5'), 32).to_s #=> "0.52359877559829887307710723054658e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 424 def asinh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :asinh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :asinh) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result * x.infinite? if x.infinite? return -asinh(-x, prec) if x < 0 sqrt_prec = prec + [-x.exponent, 0].max + BigDecimal.double_fig log(x + sqrt(x**2 + 1, sqrt_prec), prec) end
Computes the inverse hyperbolic sine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.asinh(BigDecimal('1'), 32).to_s #=> "0.88137358701954302523260932497979e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 281 def atan(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :atan) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :atan) return BigDecimal::Internal.nan_computation_result if x.nan? n = prec + BigDecimal.double_fig pi = PI(n) x = -x if neg = x < 0 return pi.div(neg ? -2 : 2, prec) if x.infinite? return pi.div(neg ? -4 : 4, prec) if x.round(n) == 1 x = BigDecimal("1").div(x, n) if inv = x > 1 x = (-1 + sqrt(1 + x.mult(x, n), n)).div(x, n) if dbl = x > 0.5 y = x d = y t = x r = BigDecimal("3") x2 = x.mult(x,n) while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig t = -t.mult(x2,n) d = t.div(r,m) y += d r += 2 end y *= 2 if dbl y = pi / 2 - y if inv y = -y if neg y.mult(1, prec) end
Computes the arctangent of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.atan(BigDecimal('-1'), 32).to_s #=> "-0.78539816339744830961566084581988e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 319 def atan2(y, x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :atan2) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :atan2) y = BigDecimal::Internal.coerce_to_bigdecimal(y, prec, :atan2) return BigDecimal::Internal.nan_computation_result if x.nan? || y.nan? if x.infinite? || y.infinite? one = BigDecimal(1) zero = BigDecimal(0) x = x.infinite? ? (x > 0 ? one : -one) : zero y = y.infinite? ? (y > 0 ? one : -one) : y.sign * zero end return x.sign >= 0 ? BigDecimal(0) : y.sign * PI(prec) if y.zero? y = -y if neg = y < 0 xlarge = y.abs < x.abs prec2 = prec + BigDecimal.double_fig if x > 0 v = xlarge ? atan(y.div(x, prec2), prec) : PI(prec2) / 2 - atan(x.div(y, prec2), prec2) else v = xlarge ? PI(prec2) - atan(-y.div(x, prec2), prec2) : PI(prec2) / 2 + atan(x.div(-y, prec2), prec2) end v.mult(neg ? -1 : 1, prec) end
Computes the arctangent of y and x to the specified number of digits of precision, numeric.
BigMath.atan2(BigDecimal('-1'), BigDecimal('1'), 32).to_s #=> "-0.78539816339744830961566084581988e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 467 def atanh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :atanh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :atanh) raise Math::DomainError, "Out of domain argument for atanh" if x < -1 || x > 1 return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result if x == 1 return -BigDecimal::Internal.infinity_computation_result if x == -1 prec2 = prec + BigDecimal.double_fig (log(x + 1, prec2) - log(1 - x, prec2)).div(2, prec) end
Computes the inverse hyperbolic tangent of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.atanh(BigDecimal('0.5'), 32).to_s #=> "0.54930614433405484569762261846126e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 106 def cbrt(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :cbrt) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :cbrt) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result * x.infinite? if x.infinite? return BigDecimal(0) if x.zero? x = -x if neg = x < 0 ex = x.exponent / 3 x = x._decimal_shift(-3 * ex) y = BigDecimal(Math.cbrt(x.to_f), 0) precs = [prec + BigDecimal.double_fig] precs << 2 + precs.last / 2 while precs.last > BigDecimal.double_fig precs.reverse_each do |p| y = (2 * y + x.div(y, p).div(y, p)).div(3, p) end y._decimal_shift(ex).mult(neg ? -1 : 1, prec) end
Computes the cube root of decimal to the specified number of digits of precision, numeric.
BigMath.cbrt(BigDecimal('2'), 32).to_s #=> "0.12599210498948731647672106072782e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 192 def cos(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :cos) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :cos) return BigDecimal::Internal.nan_computation_result if x.infinite? || x.nan? sign, x = _sin_periodic_reduction(x, prec + BigDecimal.double_fig, add_half_pi: true) sign * sin(x, prec) end
Computes the cosine of decimal to the specified number of digits of precision, numeric.
If decimal is Infinity or NaN, returns NaN.
BigMath.cos(BigMath.PI(16), 32).to_s #=> "-0.99999999999999999999999999999997e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 379 def cosh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :cosh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :cosh) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result if x.infinite? prec2 = prec + BigDecimal.double_fig e = exp(x, prec2) (e + BigDecimal(1).div(e, prec2)).div(2, prec) end
Computes the hyperbolic cosine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.cosh(BigDecimal('1'), 32).to_s #=> "0.15430806348152437784779056207571e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 597 def erf(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :erf) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :erf) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal(x.infinite?) if x.infinite? return BigDecimal(0) if x == 0 return -erf(-x, prec) if x < 0 return BigDecimal(1) if x > 5000000000 # erf(5000000000) > 1 - 1e-10000000000000000000 if x > 8 xf = x.to_f log10_erfc = -xf ** 2 / Math.log(10) - Math.log10(xf * Math::PI ** 0.5) erfc_prec = [prec + log10_erfc.ceil, 1].max erfc = _erfc_asymptotic(x, erfc_prec) if erfc # Workaround for https://github.com/ruby/bigdecimal/issues/464 return BigDecimal(1) if erfc.exponent < -prec - BigDecimal.double_fig return BigDecimal(1).sub(erfc, prec) end end prec2 = prec + BigDecimal.double_fig x_smallprec = x.mult(1, Integer.sqrt(prec2) / 2) # Taylor series of x with small precision is fast erf1 = _erf_taylor(x_smallprec, BigDecimal(0), BigDecimal(0), prec2) # Taylor series converges quickly for small x _erf_taylor(x - x_smallprec, x_smallprec, erf1, prec2).mult(1, prec) end
erf(decimal, numeric) -> BigDecimal
Computes the error function of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.erf(BigDecimal('1'), 32).to_s #=> "0.84270079294971486934122063508261e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 638 def erfc(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :erfc) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :erfc) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal(1 - x.infinite?) if x.infinite? return BigDecimal(1).sub(erf(x, prec + BigDecimal.double_fig), prec) if x < 0 return BigDecimal(0) if x > 5000000000 # erfc(5000000000) < 1e-10000000000000000000 (underflow) if x >= 8 y = _erfc_asymptotic(x, prec) return y.mult(1, prec) if y end # erfc(x) = 1 - erf(x) < exp(-x**2)/x/sqrt(pi) # Precision of erf(x) needs about log10(exp(-x**2)) extra digits log10 = 2.302585092994046 high_prec = prec + BigDecimal.double_fig + (x.ceil**2 / log10).ceil BigDecimal(1).sub(erf(x, high_prec), prec) end
Computes the complementary error function of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.erfc(BigDecimal('10'), 32).to_s #=> "0.20884875837625447570007862949578e-44"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal.rb, line 332 def exp(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :exp) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :exp) return BigDecimal::Internal.nan_computation_result if x.nan? return x.positive? ? BigDecimal::Internal.infinity_computation_result : BigDecimal(0) if x.infinite? return BigDecimal(1) if x.zero? # exp(x * 10**cnt) = exp(x)**(10**cnt) cnt = x < -1 || x > 1 ? x.exponent : 0 prec2 = prec + BigDecimal.double_fig + cnt x = x._decimal_shift(-cnt) # Calculation of exp(small_prec) is fast because calculation of x**n is fast # Calculation of exp(small_abs) converges fast. # exp(x) = exp(small_prec_part + small_abs_part) = exp(small_prec_part) * exp(small_abs_part) x_small_prec = x.round(Integer.sqrt(prec2)) y = _exp_taylor(x_small_prec, prec2).mult(_exp_taylor(x.sub(x_small_prec, prec2), prec2), prec2) # calculate exp(x * 10**cnt) from exp(x) # exp(x * 10**k) = exp(x * 10**(k - 1)) ** 10 cnt.times do y2 = y.mult(y, prec2) y5 = y2.mult(y2, prec2).mult(y, prec2) y = y5.mult(y5, prec2) end y.mult(1, prec) end
Computes the value of e (the base of natural logarithms) raised to the power of decimal, to the specified number of digits of precision.
If decimal is infinity, returns Infinity.
If decimal is NaN, returns NaN.
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 559 def expm1(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :expm1) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :expm1) return BigDecimal(-1) if x.infinite? == -1 exp_prec = prec if x < -1 # log10(exp(x)) = x * log10(e) lg_e = 0.4342944819032518 exp_prec = prec + (lg_e * x).ceil + BigDecimal.double_fig elsif x < 1 exp_prec = prec - x.exponent + BigDecimal.double_fig else exp_prec = prec end return BigDecimal(-1) if exp_prec <= 0 exp = exp(x, exp_prec) if exp.exponent > prec + BigDecimal.double_fig # Workaroudn for https://github.com/ruby/bigdecimal/issues/464 exp else exp.sub(1, prec) end end
Computes exp(decimal) - 1 to the specified number of digits of precision, numeric.
BigMath.expm1(BigDecimal('0.1'), 32).to_s #=> "0.10517091807564762481170782649025e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 868 def frexp(x) x = BigDecimal::Internal.coerce_to_bigdecimal(x, 0, :frexp) return [x, 0] unless x.finite? exponent = x.exponent [x._decimal_shift(-exponent), exponent] end
Decomposes x into a normalized fraction and an integral power of ten.
BigMath.frexp(BigDecimal(123.456)) #=> [0.123456e0, 3]
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 729 def gamma(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :gamma) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :gamma) prec2 = prec + BigDecimal.double_fig if x < 0.5 raise Math::DomainError, 'Numerical argument is out of domain - gamma' if x.frac.zero? # Euler's reflection formula: gamma(z) * gamma(1-z) = pi/sin(pi*z) pi = PI(prec2) sin = _sinpix(x, pi, prec2) return pi.div(gamma(1 - x, prec2).mult(sin, prec2), prec) elsif x.frac.zero? && x < 1000 * prec return _gamma_positive_integer(x, prec2).mult(1, prec) end a, sum = _gamma_spouge_sum_part(x, prec2) (x + (a - 1)).power(x - 0.5, prec2).mult(BigMath.exp(1 - x, prec2), prec2).mult(sum, prec) end
Computes the gamma function of decimal to the specified number of digits of precision, numeric.
BigMath.gamma(BigDecimal('0.5'), 32).to_s #=> "0.17724538509055160272981674833411e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 134 def hypot(x, y, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :hypot) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :hypot) y = BigDecimal::Internal.coerce_to_bigdecimal(y, prec, :hypot) return BigDecimal::Internal.nan_computation_result if x.nan? || y.nan? return BigDecimal::Internal.infinity_computation_result if x.infinite? || y.infinite? prec2 = prec + BigDecimal.double_fig sqrt(x.mult(x, prec2) + y.mult(y, prec2), prec) end
Returns sqrt(x**2 + y**2) to the specified number of digits of precision, numeric.
BigMath.hypot(BigDecimal('1'), BigDecimal('2'), 32).to_s #=> "0.22360679774997896964091736687313e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 885 def ldexp(x, exponent) x = BigDecimal::Internal.coerce_to_bigdecimal(x, 0, :ldexp) x.finite? ? x._decimal_shift(exponent) : x end
Inverse of frexp. Returns the value of fraction * 10**exponent.
BigMath.ldexp(BigDecimal("0.123456e0"), 3) #=> 0.123456e3
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 757 def lgamma(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :lgamma) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :lgamma) prec2 = prec + BigDecimal.double_fig if x < 0.5 return [BigDecimal::INFINITY, 1] if x.frac.zero? loop do # Euler's reflection formula: gamma(z) * gamma(1-z) = pi/sin(pi*z) pi = PI(prec2) sin = _sinpix(x, pi, prec2) log_gamma = BigMath.log(pi, prec2).sub(lgamma(1 - x, prec2).first + BigMath.log(sin.abs, prec2), prec) return [log_gamma, sin > 0 ? 1 : -1] if prec2 + log_gamma.exponent > prec + BigDecimal.double_fig # Retry with higher precision if loss of significance is too large prec2 = prec2 * 3 / 2 end elsif x.frac.zero? && x < 1000 * prec log_gamma = BigMath.log(_gamma_positive_integer(x, prec2), prec) [log_gamma, 1] else # if x is close to 1 or 2, increase precision to reduce loss of significance diff1_exponent = (x - 1).exponent diff2_exponent = (x - 2).exponent extremely_near_one = diff1_exponent < -prec2 extremely_near_two = diff2_exponent < -prec2 if extremely_near_one || extremely_near_two # If x is extreamely close to base = 1 or 2, linear interpolation is accurate enough. # Taylor expansion at x = base is: (x - base) * digamma(base) + (x - base) ** 2 * trigamma(base) / 2 + ... # And we can ignore (x - base) ** 2 and higher order terms. base = extremely_near_one ? 1 : 2 d = BigDecimal(1)._decimal_shift(1 - prec2) log_gamma_d, sign = lgamma(base + d, prec2) return [log_gamma_d.mult(x - base, prec2).div(d, prec), sign] end prec2 += [-diff1_exponent, -diff2_exponent, 0].max a, sum = _gamma_spouge_sum_part(x, prec2) log_gamma = BigMath.log(sum, prec2).add((x - 0.5).mult(BigMath.log(x.add(a - 1, prec2), prec2), prec2) + 1 - x, prec) [log_gamma, 1] end end
Computes the natural logarithm of the absolute value of the gamma function of decimal to the specified number of digits of precision, numeric and its sign.
BigMath.lgamma(BigDecimal('0.5'), 32) #=> [0.57236494292470008707171367567653e0, 1]
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal.rb, line 255 def log(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :log) raise Math::DomainError, 'Complex argument for BigMath.log' if Complex === x x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :log) return BigDecimal::Internal.nan_computation_result if x.nan? raise Math::DomainError, 'Negative argument for log' if x < 0 return -BigDecimal::Internal.infinity_computation_result if x.zero? return BigDecimal::Internal.infinity_computation_result if x.infinite? return BigDecimal(0) if x == 1 prec2 = prec + BigDecimal.double_fig BigDecimal.save_limit do BigDecimal.limit(0) if x > 10 || x < 0.1 log10 = log(BigDecimal(10), prec2) exponent = x.exponent x = x._decimal_shift(-exponent) if x < 0.3 x *= 10 exponent -= 1 end return (log10 * exponent).add(log(x, prec2), prec) end x_minus_one_exponent = (x - 1).exponent # log(x) = log(sqrt(sqrt(sqrt(sqrt(x))))) * 2**sqrt_steps sqrt_steps = [Integer.sqrt(prec2) + 3 * x_minus_one_exponent, 0].max lg2 = 0.3010299956639812 sqrt_prec = prec2 + [-x_minus_one_exponent, 0].max + (sqrt_steps * lg2).ceil sqrt_steps.times do x = x.sqrt(sqrt_prec) end # Taylor series for log(x) around 1 # log(x) = -log((1 + X) / (1 - X)) where X = (x - 1) / (x + 1) # log(x) = 2 * (X + X**3 / 3 + X**5 / 5 + X**7 / 7 + ...) x = (x - 1).div(x + 1, sqrt_prec) y = x x2 = x.mult(x, prec2) 1.step do |i| n = prec2 + x.exponent - y.exponent + x2.exponent break if n <= 0 || x.zero? x = x.mult(x2.round(n - x2.exponent), n) y = y.add(x.div(2 * i + 1, n), prec2) end y.mult(2 ** (sqrt_steps + 1), prec) end end
Computes the natural logarithm of decimal to the specified number of digits of precision, numeric.
If decimal is zero or negative, raises Math::DomainError.
If decimal is positive infinity, returns Infinity.
If decimal is NaN, returns NaN.
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 522 def log10(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :log10) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :log10) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result if x.infinite? == 1 prec2 = prec + BigDecimal.double_fig * 3 / 2 v = log(x, prec2).div(log(BigDecimal(10), prec2), prec2) # Perform half-up rounding to calculate log10(10**n)==n correctly in every rounding mode v = v.round(prec + BigDecimal.double_fig - (v.exponent < 0 ? v.exponent : 0), BigDecimal::ROUND_HALF_UP) v.mult(1, prec) end
Computes the base 10 logarithm of decimal to the specified number of digits of precision, numeric.
If decimal is zero or negative, raises Math::DomainError.
If decimal is positive infinity, returns Infinity.
If decimal is NaN, returns NaN.
BigMath.log10(BigDecimal('3'), 32).to_s #=> "0.47712125471966243729502790325512e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 543 def log1p(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :log1p) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :log1p) raise Math::DomainError, 'Out of domain argument for log1p' if x < -1 return log(x + 1, prec) end
Computes log(1 + decimal) to the specified number of digits of precision, numeric.
BigMath.log1p(BigDecimal('0.1'), 32).to_s #=> "0.95310179804324860043952123280765e-1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 494 def log2(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :log2) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :log2) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result if x.infinite? == 1 prec2 = prec + BigDecimal.double_fig * 3 / 2 v = log(x, prec2).div(log(BigDecimal(2), prec2), prec2) # Perform half-up rounding to calculate log2(2**n)==n correctly in every rounding mode v = v.round(prec + BigDecimal.double_fig - (v.exponent < 0 ? v.exponent : 0), BigDecimal::ROUND_HALF_UP) v.mult(1, prec) end
Computes the base 2 logarithm of decimal to the specified number of digits of precision, numeric.
If decimal is zero or negative, raises Math::DomainError.
If decimal is positive infinity, returns Infinity.
If decimal is NaN, returns NaN.
BigMath.log2(BigDecimal('3'), 32).to_s #=> "0.15849625007211561814537389439478e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 155 def sin(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :sin) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :sin) return BigDecimal::Internal.nan_computation_result if x.infinite? || x.nan? n = prec + BigDecimal.double_fig one = BigDecimal("1") two = BigDecimal("2") sign, x = _sin_periodic_reduction(x, n) x1 = x x2 = x.mult(x,n) y = x d = y i = one z = one while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig x1 = -x2.mult(x1,n) i += two z *= (i-one) * i d = x1.div(z,m) y += d end y = BigDecimal("1") if y > 1 y.mult(sign, prec) end
Computes the sine of decimal to the specified number of digits of precision, numeric.
If decimal is Infinity or NaN, returns NaN.
BigMath.sin(BigMath.PI(5)/4, 32).to_s #=> "0.70710807985947359435812921837984e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 356 def sinh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :sinh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :sinh) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal::Internal.infinity_computation_result * x.infinite? if x.infinite? prec2 = prec + BigDecimal.double_fig prec2 -= x.exponent if x.exponent < 0 e = exp(x, prec2) (e - BigDecimal(1).div(e, prec2)).div(2, prec) end
Computes the hyperbolic sine of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.sinh(BigDecimal('1'), 32).to_s #=> "0.11752011936438014568823818505956e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 64 def sqrt(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :sqrt) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :sqrt) x.sqrt(prec) end
Computes the square root of decimal to the specified number of digits of precision, numeric.
BigMath.sqrt(BigDecimal('2'), 32).to_s #=> "0.14142135623730950488016887242097e1"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 214 def tan(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :tan) sin(x, prec + BigDecimal.double_fig).div(cos(x, prec + BigDecimal.double_fig), prec) end
Computes the tangent of decimal to the specified number of digits of precision, numeric.
If decimal is Infinity or NaN, returns NaN.
BigMath.tan(BigDecimal("0.0"), 4).to_s #=> "0.0" BigMath.tan(BigMath.PI(24) / 4, 32).to_s #=> "0.99999999999999999999999830836025e0"
Source
# File vendor/bundle/ruby/4.0.0/gems/bigdecimal-4.0.1/lib/bigdecimal/math.rb, line 401 def tanh(x, prec) prec = BigDecimal::Internal.coerce_validate_prec(prec, :tanh) x = BigDecimal::Internal.coerce_to_bigdecimal(x, prec, :tanh) return BigDecimal::Internal.nan_computation_result if x.nan? return BigDecimal(x.infinite?) if x.infinite? prec2 = prec + BigDecimal.double_fig + [-x.exponent, 0].max e = exp(x, prec2) einv = BigDecimal(1).div(e, prec2) (e - einv).div(e + einv, prec) end
Computes the hyperbolic tangent of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.tanh(BigDecimal('1'), 32).to_s #=> "0.76159415595576488811945828260479e0"