Package squidpony.squidmath

Class MathExtras

java.lang.Object
squidpony.squidmath.MathExtras
public final class MathExtras
extends Object
Mathematical operations not provided by java.lang.Math.
Originally part of the Uncommon Maths software package as Maths.
Author:
Daniel Dyer

  • Method Summary

    Modifier and Type Method Description
    static boolean approxEquals​(double value1, double value2, double tolerance)
    Checks that two values are approximately equal (plus or minus a specified tolerance).
    static BigInteger bigFactorial​(int n)
    Calculates the factorial of n where n is a positive integer.
    static double clamp​(double value, double min, double max)
    If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
    static float clamp​(float value, float min, float max)
    If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
    static int clamp​(int value, int min, int max)
    If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
    static long clamp​(long value, long min, long max)
    If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
    static long factorial​(int n)
    Calculates the factorial of n where n is a number in the range 0 - 20.
    static long greatestCommonDivisor​(long a, long b)
    Determines the greatest common divisor of a pair of natural numbers using the Euclidean algorithm.
    static double log​(double base, double arg)
    Calculate logarithms for arbitrary bases.
    static int modularMultiplicativeInverse​(int a)
    Given any odd int a, this finds another odd int b such that a * b == 1.
    static long modularMultiplicativeInverse​(long a)
    Given any odd long a, this finds another odd long b such that a * b == 1L.
    static long raiseToPower​(int value, int power)
    Calculate the first argument raised to the power of the second.
    static double remainder​(double op, double d)
    Like the modulo operator %, but the result will always match the sign of d instead of op.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • factorial

      public static long factorial​(int n)
      Calculates the factorial of n where n is a number in the range 0 - 20. Zero factorial is equal to 1. For values of n greater than 20 you must use bigFactorial(int).
      Parameters:
      n - The factorial to calculate.
      Returns:
      The factorial of n.
      See Also:
      bigFactorial(int)

    • bigFactorial

      public static BigInteger bigFactorial​(int n)
      Calculates the factorial of n where n is a positive integer. Zero factorial is equal to 1. For values of n up to 20, consider using factorial(int) instead since it uses a faster implementation.
      Parameters:
      n - The factorial to calculate.
      Returns:
      The factorial of n.
      See Also:
      factorial(int)

    • raiseToPower

      public static long raiseToPower​(int value, int power)
      Calculate the first argument raised to the power of the second. This method only supports non-negative powers.
      Parameters:
      value - The number to be raised.
      power - The exponent (must be positive).
      Returns:
      value raised to power.

    • log

      public static double log​(double base, double arg)
      Calculate logarithms for arbitrary bases.
      Parameters:
      base - The base for the logarithm.
      arg - The value to calculate the logarithm for.
      Returns:
      The log of arg in the specified base.

    • approxEquals

      public static boolean approxEquals​(double value1, double value2, double tolerance)
      Checks that two values are approximately equal (plus or minus a specified tolerance).
      Parameters:
      value1 - The first value to compare.
      value2 - The second value to compare.
      tolerance - How much (in percentage terms, as a percentage of the first value) the values are allowed to differ and still be considered equal. Expressed as a value between 0 and 1.
      Returns:
      true if the values are approximately equal, false otherwise.

    • clamp

      public static int clamp​(int value, int min, int max)
      If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
      Parameters:
      value - The value to check.
      min - The minimum permitted value.
      max - The maximum permitted value.
      Returns:
      value if it is between the specified limits, min if the value is too low, or max if the value is too high.

    • clamp

      public static long clamp​(long value, long min, long max)
      If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
      Parameters:
      value - The value to check.
      min - The minimum permitted value.
      max - The maximum permitted value.
      Returns:
      value if it is between the specified limits, min if the value is too low, or max if the value is too high.

    • clamp

      public static double clamp​(double value, double min, double max)
      If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
      Parameters:
      value - The value to check.
      min - The minimum permitted value.
      max - The maximum permitted value.
      Returns:
      value if it is between the specified limits, min if the value is too low, or max if the value is too high.

    • clamp

      public static float clamp​(float value, float min, float max)
      If the specified value is not greater than or equal to the specified minimum and less than or equal to the specified maximum, adjust it so that it is.
      Parameters:
      value - The value to check.
      min - The minimum permitted value.
      max - The maximum permitted value.
      Returns:
      value if it is between the specified limits, min if the value is too low, or max if the value is too high.

    • remainder

      public static double remainder​(double op, double d)
      Like the modulo operator %, but the result will always match the sign of d instead of op.
      Parameters:
      op - the dividend; negative values are permitted and wrap instead of producing negative results
      d - the divisor; if this is negative then the result will be negative, otherwise it will be positive
      Returns:
      the remainder of the division of op by d, with a sign matching d

    • greatestCommonDivisor

      public static long greatestCommonDivisor​(long a, long b)
      Determines the greatest common divisor of a pair of natural numbers using the Euclidean algorithm. This method only works with natural numbers. If negative integers are passed in, the absolute values will be used. The return value is always positive.
      Parameters:
      a - The first value.
      b - The second value.
      Returns:
      The greatest common divisor.

    • modularMultiplicativeInverse

      public static int modularMultiplicativeInverse​(int a)
      Given any odd int a, this finds another odd int b such that a * b == 1.
      This is incompatible with GWT, but it should usually only find uses in exploratory code or in tests anyway... It is only incompatible because it tends to rely on multiplication overflow to work.
      Parameters:
      a - any odd int; note that even numbers do not have inverses modulo 2 to the 32
      Returns:
      the multiplicative inverse of a modulo 4294967296 (or, 2 to the 32)

    • modularMultiplicativeInverse

      public static long modularMultiplicativeInverse​(long a)
      Given any odd long a, this finds another odd long b such that a * b == 1L.
      Parameters:
      a - any odd long; note that even numbers do not have inverses modulo 2 to the 64
      Returns:
      the multiplicative inverse of a modulo 18446744073709551616 (or, 2 to the 64)