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path: root/ext/bigdecimal/lib/bigdecimal/math.rb
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 ``` ``````# # Contents: # sin(x, prec) # cos(x, prec) # exp(x, prec) # log(x, prec) # PI (prec) # # where: # x ... BigDecimal number to be computed. # prec ... Number of digits to be obtained. # module BigMath def sin(x, prec) raise ArgumentError, "Zero or negative precision for sin" if prec <= 0 return BigDecimal("NaN") if x.infinite? || x.nan? n = prec + BigDecimal.double_fig n2 = n+n one = BigDecimal("1") two = BigDecimal("2") x1 = x x2 = x * x sign = 1 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 sign = -sign x1 = x2.mult(x1,n2) i += two z *= (i-one) * i d = sign * x1.div(z,m) y += d end y end def cos(x, prec) raise ArgumentError, "Zero or negative precision for sin" if prec <= 0 return BigDecimal("NaN") if x.infinite? || x.nan? n = prec + BigDecimal.double_fig n2 = n+n one = BigDecimal("1") two = BigDecimal("2") x1 = one x2 = x * x sign = 1 y = one d = y i = BigDecimal("0") z = one while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig sign = -sign x1 = x2.mult(x1,n2) i += two z *= (i-one) * i d = sign * x1.div(z,m) y += d end y end def exp(x, prec) raise ArgumentError, "Zero or negative precision for sin" if prec <= 0 return BigDecimal("NaN") if x.infinite? || x.nan? n = prec + BigDecimal.double_fig n2 = n+n one = BigDecimal("1") x1 = one y = one d = y z = one i = 0 while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig x1 = x1.mult(x,n2) i += 1 z *= i d = x1.div(z,m) y += d end y end def log(x, prec) raise ArgumentError, "Zero or negative argument for log" if x <= 0 || prec <= 0 return x if x.infinite? || x.nan? one = BigDecimal("1") two = BigDecimal("2") n = prec + BigDecimal.double_fig n2 = n + n x = (x - one).div(x + one,n) x2 = x * x y = two * x d = y i = one while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0) m = BigDecimal.double_fig if m < BigDecimal.double_fig x = x2.mult(x,n2) i += two d = (two * x).div(i,m) y += d end y end def PI(prec) raise ArgumentError, "Zero or negative argument for PI" if prec <= 0 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 w = 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 w = 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,m) d = t.div(k,m) pi = pi + d k = k+two end pi end end ``````