src/harmony-math.js

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'use strict';

// ES6 draft 09-27-13, section 20.2.2.28.
function MathSign(x) {
  x = TO_NUMBER_INLINE(x);
  if (x > 0) return 1;
  if (x < 0) return -1;
  if (x === 0) return x;
  return NAN;
}


// ES6 draft 09-27-13, section 20.2.2.34.
function MathTrunc(x) {
  x = TO_NUMBER_INLINE(x);
  if (x > 0) return MathFloor(x);
  if (x < 0) return MathCeil(x);
  if (x === 0) return x;
  return NAN;
}


// ES6 draft 09-27-13, section 20.2.2.30.
function MathSinh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  // Idempotent for NaN, +/-0 and +/-Infinity.
  if (x === 0 || !NUMBER_IS_FINITE(x)) return x;
  return (MathExp(x) - MathExp(-x)) / 2;
}


// ES6 draft 09-27-13, section 20.2.2.12.
function MathCosh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  // Idempotent for NaN and +/-Infinity.
  if (!NUMBER_IS_FINITE(x)) return x;
  return (MathExp(x) + MathExp(-x)) / 2;
}


// ES6 draft 09-27-13, section 20.2.2.33.
function MathTanh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  // Idempotent for +/-0.
  if (x === 0) return x;
  // Returns +/-1 for +/-Infinity.
  if (!NUMBER_IS_FINITE(x)) return MathSign(x);
  var exp1 = MathExp(x);
  var exp2 = MathExp(-x);
  return (exp1 - exp2) / (exp1 + exp2);
}


// ES6 draft 09-27-13, section 20.2.2.5.
function MathAsinh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  // Idempotent for NaN, +/-0 and +/-Infinity.
  if (x === 0 || !NUMBER_IS_FINITE(x)) return x;
  if (x > 0) return MathLog(x + MathSqrt(x * x + 1));
  // This is to prevent numerical errors caused by large negative x.
  return -MathLog(-x + MathSqrt(x * x + 1));
}


// ES6 draft 09-27-13, section 20.2.2.3.
function MathAcosh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  if (x < 1) return NAN;
  // Idempotent for NaN and +Infinity.
  if (!NUMBER_IS_FINITE(x)) return x;
  return MathLog(x + MathSqrt(x + 1) * MathSqrt(x - 1));
}


// ES6 draft 09-27-13, section 20.2.2.7.
function MathAtanh(x) {
  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
  // Idempotent for +/-0.
  if (x === 0) return x;
  // Returns NaN for NaN and +/- Infinity.
  if (!NUMBER_IS_FINITE(x)) return NAN;
  return 0.5 * MathLog((1 + x) / (1 - x));
}


function ExtendMath() {
  %CheckIsBootstrapping();

  // Set up the non-enumerable functions on the Math object.
  InstallFunctions($Math, DONT_ENUM, $Array(
    "sign", MathSign,
    "trunc", MathTrunc,
    "sinh", MathSinh,
    "cosh", MathCosh,
    "tanh", MathTanh,
    "asinh", MathAsinh,
    "acosh", MathAcosh,
    "atanh", MathAtanh
  ));
}

ExtendMath();