diff options
Diffstat (limited to 'ext/bigdecimal/lib/bigdecimal')
| -rw-r--r-- | ext/bigdecimal/lib/bigdecimal/math.rb | 44 |
1 files changed, 20 insertions, 24 deletions
diff --git a/ext/bigdecimal/lib/bigdecimal/math.rb b/ext/bigdecimal/lib/bigdecimal/math.rb index 7f3c293268..f6a3ff6a62 100644 --- a/ext/bigdecimal/lib/bigdecimal/math.rb +++ b/ext/bigdecimal/lib/bigdecimal/math.rb @@ -10,14 +10,15 @@ # # where: # x ... BigDecimal number to be computed. +# |x| must be small enough to get convergence. # prec ... Number of digits to be obtained. # # Usage: # require "bigdecimal" # require "bigdecimal/math.rb" # include BigMath -# a = BigDecimal((PI(1000)/2).to_s) -# puts sin(a,1000) # => 0.10000000000000000000......E1 +# a = BigDecimal((PI(100)/2).to_s) +# puts sin(a,100) # => 0.10000000000000000000......E1 # module BigMath def sqrt(x,prec) @@ -28,11 +29,10 @@ module BigMath 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 + x2 = x.mult(x,n) sign = 1 y = x d = y @@ -41,7 +41,7 @@ module BigMath 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) + x1 = x2.mult(x1,n) i += two z *= (i-one) * i d = sign * x1.div(z,m) @@ -54,11 +54,10 @@ module BigMath 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 + x2 = x.mult(x,n) sign = 1 y = one d = y @@ -67,7 +66,7 @@ module BigMath 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) + x1 = x2.mult(x1,n) i += two z *= (i-one) * i d = sign * x1.div(z,m) @@ -81,15 +80,14 @@ module BigMath return BigDecimal("NaN") if x.infinite? || x.nan? raise ArgumentError, "x.abs must be less than 1.0" if x.abs>=1 n = prec + BigDecimal.double_fig - n2 = n+n - y = x; - d = y; - t = x; - r = BigDecimal("3"); - x2 = x*x + 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,n2) + t = -t.mult(x2,n) d = t.div(r,m) y += d r += 2 @@ -101,7 +99,6 @@ module BigMath 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 @@ -110,7 +107,7 @@ module BigMath 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) + x1 = x1.mult(x,n) i += 1 z *= i d = x1.div(z,m) @@ -125,20 +122,19 @@ module BigMath 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 + x2 = x.mult(x,n) + y = 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) + x = x2.mult(x,n) i += two - d = (two * x).div(i,m) + d = x.div(i,m) y += d end - y + y*two end def PI(prec) @@ -171,7 +167,7 @@ module BigMath 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) + t = t.div(m57121,n) d = t.div(k,m) pi = pi + d k = k+two |