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Built in Functions » Histórico » Versión 8

Federico Vera, 2018-07-08 05:55

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# Built in Functions
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There are a number of built-in functions, that usually just map with the corresponding [`java.util.Math`](https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html) methods (so all of the same restrictions apply), this functions are:
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## Trigonometric Functions:
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* `sin(x)`: Sine of an angle expressed in radians
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* `cos(x)`: Cosine of an angle expressed in radians
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* `tan(x)`: Tangent of an angle expressed in radians
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## Inverse Trigonometric:
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* `asin(x)`: Arc sine in the range [-π/2, π/2)
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* `acos(x)`: Arc cosine in the range [0, π)
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* `atan(x)`: Arc tangent in the range [-π/2, π/2) 
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## Hyperbolic Functions:
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* `sinh(x)`: Hyperbolic sine `(e^x - e^(-x)) / 2`
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* `cosh(x)`: Hyperbolic cosine `(e^x + e^(-x)) / 2`
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* `tanh(x)`: Hyperbolic tangent `(e^x - e^(-x)) / (e^x + e^(-x))`
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## Logarithms
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* `log(x)`: Base 10 logarithm of `x` 
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* `log1p(x)`: Base 10 logarithm of `(x + 1)`
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* `log10(x)`: Base 10 logarithm of `x`
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* `log2(x)`: Base 2 logarithm of `x`
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## Misc
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* `pow(b, e)`: `b` to the power of `e`
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* `sqrt(x)`: Square root of `x`
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* `cbrt(x)`: Cube root of `x`
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* `exp(x)`: `e` to the power of `x`
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* `expm1(x)`: `e` to the power of `x` minus 1 (`e^x - 1`)
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* `signum(x)`:{{collapse(Note)
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*This is the only method not implemented using it's corresponding `java.util.Math` method.*
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}} Signum of `x` (`-1, 0, 1` for `< 0`, `= 0` and `> 0` respectively)
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* `abs(x)`: Absolute value of `x`
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* `ceil(x)`: First integer closest to negative infinity greater than or equal `x` 
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* `floor(x)`: First integer closest to positive infinity less than or equal `x` 
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## Constants
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* `pi()`: Ratio of the circumference of a circle to its diameter `3.14159265358979323846`
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* `e()`: Base of the natural logarithm `2.7182818284590452354`
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## Disabling built-in functions
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Since version `0.6-riddler` (commit:28c731ea) you can disable all built-in functions like this:
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~~~Java
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    Expression e = new ExpressionBuilder("x + 3")
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                      .disableBuiltInFunctions() //<--
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                      .variable("x")
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                      .build();
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~~~
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Remember that since constants are also defined as functions this will also disable them.
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## Code
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The code for the functions is [here](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/entry/src/main/java/net/objecthunter/exp4j/function/Functions.java).
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