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Funciones y Operadores adicionales » History » Version 1

Federico Vera, 2018-07-12 17:38

1 1 Federico Vera
# Funciones y Operadores adicionales
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There are a number of extra functions and operators included in this version of `exp4j`, non of this are enabled by default, they are in the [`net.objecthunter.exp4j.extras`](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/show/src/main/java/net/objecthunter/exp4j/extras) package.
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## Comparison Operators
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Aside from the arithmetic operators several comparison operators are included: `<`, `<=`, `>`, `>=`, `!=` and `==`. 
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Please note that since `exp4j` itself has no concept of `boolean`, the results given by all of the comparison operators will be `1.0` if `true` and `0.0` if `false`. Let it be noted that due to rounding, equality operators use a radix in which they consider numbers to be "equal", that is:
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Let `a` and `b` be two real numbers, `a == b` will evaluate to `true` if and only if the distance between `a` and `b` (`dist(a, b) := abs(a - b)`) is less or equal than [`1e-12` (`0.000000000001`)](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/entry/src/main/java/net/objecthunter/exp4j/extras/FunctionsMisc.java#L38) and `false` otherwise.
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### Precedence
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Operator precedence is altered when using the comparison operators, the new precedence is:
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~~~
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FIRST->  * / %  - +  > >= < <=  ¬  &  |  == !=   <-LAST
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         -----  ---  ---------  -  -  -  -----    
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         ^^^ The dashes indicate groups with the same precedence
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~~~
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## Funciones lógicas
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Even though we have boolean operators, there are also a number of boolean functions that can be used (some people prefer functions)
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* `and(a, b)`: Y lógico _equivalente a `a & b`_
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* `or(a, b)`: O lógico _equivalente a `a | b`_
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* `xor(a, b)`: O exclusivo
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* `nand(a, b)`: _equivalente a `¬(a & b)`_
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* `nor(a, b)`: _equivalente a `¬(a | b)`_
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* `xnor(a, b)`: O exclusivo negado 
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* `not(a)`: _equivalente a `¬a`_
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## Constantes lógicas
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* `true()`: verdadero (`1.0`) (se considera como verdadero a cualquier valor distinto de cero, pero la función `true()` devuelve `1.0` así como los operadores booleans y de comparación.
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* `false()`: falso (`0.0`)
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## Extra Functions
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* `if(e, v_true, v_false)`: Branches the formula, it will be evaluated as `v_true` if `e == true()` and `v_false`  if `e == false()` 
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* `equals(a, b)`: Equivalent to `a == b`, so the same conditions apply.
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* `sinc(x)`: [Cardinal sine of `x`](https://en.wikipedia.org/wiki/Sinc_function) (not normalized), equivalent to `sin(x)/x`
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## Code
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El código está [aquí](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/entry/src/main/java/net/objecthunter/exp4j/extras/OperatorsComparison.java), [aquí](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/entry/src/main/java/net/objecthunter/exp4j/extras/FunctionsMisc.java) u [aquí](https://redmine.riddler.com.ar/projects/exp4j/repository/revisions/master/entry/src/main/java/net/objecthunter/exp4j/extras/FunctionsBoolean.java).
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