sdk/lib/math/base.dart

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// A part of the dart:math library.

/**
 * Base of the natural logarithms.
 *
 * Typically written as "e".
 */
const double E = 2.718281828459045;

/**
 * Natural logarithm of 10.
 */
const double LN10 =  2.302585092994046;

/**
 * Natural logarithm of 2.
 */
const double LN2 =  0.6931471805599453;

/**
 * Base-2 logarithm of [E].
 */
const double LOG2E = 1.4426950408889634;

/**
 * Base-10 logarithm of [E].
 */
const double LOG10E = 0.4342944819032518;

/**
 * The PI constant.
 */
const double PI = 3.1415926535897932;

/**
 * Square root of 1/2.
 */
const double SQRT1_2 = 0.7071067811865476;

/**
 * Square root of 2.
 */
const double SQRT2 = 1.4142135623730951;

/** Temporary redirect to [int.parse]. */
int parseInt(String string) => int.parse(string);

/** Temporary redirect to [double.parse]. */
double parseDouble(String string) => double.parse(string);

/**
  * Returns the lesser of two numbers.
  *
  * Returns NaN if either argument is NaN.
  * The lesser of [:-0.0:] and [:0.0:] is [:-0.0:].
  * If the arguments are otherwise equal (including int and doubles with the
  * same mathematical value) then it is unspecified which of the two arguments
  * is returned.
  */
num min(num a, num b) {
  if (a is num) {
    // TODO(floitsch): merge this if into the previous one, once dart2js
    // correctly propagates types for logical ands.
    if (b is num) {
      if (a > b) return b;
      if (a < b) return a;
      if (b is double) {
        // Special case for NaN and -0.0. If one argument is NaN return NaN.
        // [min] must also distinguish between -0.0 and 0.0.
        if (a is double) {
          if (a == 0.0) {
            // a is either 0.0 or -0.0. b is either 0.0, -0.0 or NaN.
            // The following returns -0.0 if either a or b is -0.0, and it
            // returns NaN if b is NaN.
            return (a + b) * a * b;
          }
        }
        // Check for NaN and b == -0.0.
        if (a == 0 && b.isNegative() || b.isNaN()) return b;
        return a;
      }
      return a;
    }
    throw new IllegalArgumentException(b);
  }
  throw new IllegalArgumentException(a);
}

/**
  * Returns the larger of two numbers.
  *
  * Returns NaN if either argument is NaN.
  * The larger of [:-0.0:] and [:0.0:] is [:0.0:]. If the arguments are
  * otherwise equal (including int and doubles with the same mathematical value)
  * then it is unspecified which of the two arguments is returned.
  */
num max(num a, num b) {
  if (a is num) {
    // TODO(floitsch): merge this if into the previous one, once dart2js
    // correctly propagates types for logical ands.
    if (b is num) {
      if (a > b) return a;
      if (a < b) return b;
      if (b is double) {
        // Special case for NaN and -0.0. If one argument is NaN return NaN.
        // [max] must also distinguish between -0.0 and 0.0.
        if (a is double) {
          if (a == 0.0) {
            // a is either 0.0 or -0.0. b is either 0.0, -0.0, or NaN.
            // The following returns 0.0 if either a or b is 0.0, and it
            // returns NaN if b is NaN.
            return a + b;
          }
        }
        // Check for NaN.
        if (b.isNaN()) return b;
        return a;
      }
      // max(-0.0, 0) must return 0.
      if (b == 0 && a.isNegative()) return b;
      return a;
    }
    throw new IllegalArgumentException(b);
  }
  throw new IllegalArgumentException(a);
}

/**
 * A variant of [atan].
 *
 * Converts both arguments to doubles.
 *
 * Returns the angle between the positive x-axis and the vector ([b],[a]).
 * The result, in radians, is in the range -PI..PI.
 *
 * If [b] is positive, this is the same as [:atan(b/a):].
 *
 * The result is negative when [a] is negative (including when [a] is the
 * double -0.0).
 *
 * If [a] is equal to zero, the vector ([b],[a]) is considered parallel to
 * the x-axis, even if [b] is also equal to zero. The sign of [b] determines
 * the direction of the vector along the x-axis.
 *
 * Returns NaN if either argument is NaN.
 */
external double atan2(num a, num b);

/**
 * Returns [x] to the power of [exponent].
 *
 * If [x] is an [int] and [exponent] is a non-negative [int], the result is
 * an [int], otherwise the result it is a [double].
 *
 * Notice that an [int] result cannot overflow, but a [double] result might
 * be [double.INFINITY].
 */
external num pow(num x, num exponent);

/**
 * Converts [x] to a double and returns the sine of the value.
 *
 * If [x] is not a finite number, the result is NaN.
 */
external double sin(num x);

/**
 * Converts [x] to a double and returns the cosine of the value.
 *
 * If [x] is not a finite number, the result is NaN.
 */
external double cos(num x);

/**
 * Converts [x] to a double and returns the tangent of the value.
 *
 * The tangent function is equivalent to [:sin(x)/cos(x):] and may be
 * infinite (positive or negative) when [:cos(x):] is equal to zero.
 * If [x] is not a finite number, the result is NaN.
 */
external double tan(num x);

/**
 * Converts [x] to a double and returns the arc cosine of the value.
 *
 * Returns a value in the range -PI..PI, or NaN if [x] is outside
 * the range -1..1.
 */
external double acos(num x);

/**
 * Converts [x] to a double and returns the arc sine of the value.
 * Returns a value in the range -PI..PI, or  NaN if [x] is outside
 * the range -1..1.
 */
external double asin(num x);

/**
 * Converts [x] to a dobule and returns the arc tangent of the vlaue.
 * Returns a value in the range -PI/2..PI/2, or NaN if [x] is NaN.
 */
external double atan(num x);

/**
 * Converts [x] to a double and returns the positive square root of the value.
 *
 * Returns -0.0 if [x] is -0.0, and NaN if [x] is otherwise negative or NaN.
 */
external double sqrt(num x);

/**
 * Converts [x] to a double and returns the natural exponent, [E],
 * to the power [x].
 * Returns NaN if [x] is NaN.
 */
external double exp(num x);

/**
 * Converts [x] to a double and returns the natural logarithm of the value.
 * Returns negative infinity if [x] is equal to zero.
 * Returns NaN if [x] is NaN or less than zero.
 */
external double log(num x);