diff options
Diffstat (limited to 'src/library.js')
-rw-r--r-- | src/library.js | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/src/library.js b/src/library.js index 083ec0f1..837ed71d 100644 --- a/src/library.js +++ b/src/library.js @@ -5131,6 +5131,64 @@ LibraryManager.library = { atan2f: 'Math.atan2', exp: 'Math.exp', expf: 'Math.exp', + + // The erf and erfc functions are inspired from + // http://www.digitalmars.com/archives/cplusplus/3634.html + // and mruby source code at + // https://github.com/mruby/mruby/blob/master/src/math.c + erfc: function (x) { + var MATH_TOLERANCE = 1E-12; + var ONE_SQRTPI = 0.564189583547756287; + var a = 1; + var b = x; + var c = x; + var d = x * x + 0.5; + var n = 1.0; + var q2 = b / d; + var q1, t; + + if (Math.abs(x) < 2.2) { + return 1.0 - _erf(x); + } + if (x < 0) { + return 2.0 - _erfc(-x); + } + do { + t = a * n + b * x; + a = b; + b = t; + t = c * n + d * x; + c = d; + d = t; + n += 0.5; + q1 = q2; + q2 = b / d; + } while (Math.abs(q1 - q2) / q2 > MATH_TOLERANCE); + return (ONE_SQRTPI * Math.exp(- x * x) * q2); + }, + erfcf: 'erfcf', + erf: function (x) { + var MATH_TOLERANCE = 1E-12; + var TWO_SQRTPI = 1.128379167095512574; + var sum = x; + var term = x; + var xsqr = x*x; + var j = 1; + + if (Math.abs(x) > 2.2) { + return 1.0 - _erfc(x); + } + do { + term *= xsqr / j; + sum -= term / (2 * j + 1); + ++j; + term *= xsqr / j; + sum += term / (2 * j + 1); + ++j; + } while (Math.abs(term / sum) > MATH_TOLERANCE); + return (TWO_SQRTPI * sum); + }, + erff: 'erf', log: 'Math.log', logf: 'Math.log', sqrt: 'Math.sqrt', |