# Command: variant

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Name:

    variant - return specific variant of function

Synopsis:

    funcname signature variant -> anytype  true
      false

Examples:

      /add [/doubletype /doubletype] variant pop --> /add_dd load
      /add [/doubletype /stringtype] variant	 --> false
      /add [/stringtype /doubletype] variant	 --> false
      /ArrayQ [/anytype]	 variant pop --> false
      /f {(hello) ==} def
      /f [/integertype] variant pop --> {(hello) ==}

Description:

      The operator variant checks whether a variant of the function
      matching a particular signature is available. If so, this variant and
      the value true are returned. If not, the return value is false. If
      the literal specifying the function does not refer to a trie the
      function has only a single variant and no information about the
      signature. In this case, the unique variant is returned.  The
      operator variant can be used to optimize SLI code for speed in
      situations where it is guaranteed that a particular variant of a
      function is needed. Here, replacing the overloaded function by the
      specific variant removes the overhead of type checking. A typical
      situation in which the data types of the arguments are known is a
      function call inside a function with a specified signature (see
      example below). Another situation is machine generated SLI code where
      the machine, for example a compiler, is requested to emit optimized
      code restricted to particular data type.

      /incr [/doubletype]
      {
      1.0 add
      }
      << /add /add [/doubletype /doubletype] variant pop >> Inline
      def

Parameters:

      funcname, is a literal specifying the name of the function.
      Usually the literal refers to a trie with several
      variants.
      signature, is an array of literals defining the signature
      of the variant searched for

Author:

    Diesmann

FirstVersion:

    090201

SeeAlso:

- Inline
- CompileMath
- def
- addtotrie
- cva

Source:

    /opt/conda/conda-bld/nest_1512421404550/work/nest-2.12.0/lib/sli/typeinit.sli

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