# isdef

checks variable existence

## Calling Sequence

    isdef(name [,where])

## Arguments

name

  a character string

where

  an optional character string with default value `'all'`

## Description

`isdef(name)` returns `%T` if the variable named `name` exists and `%F` otherwise.

Caveats: a function which uses `isdef` may return a result which depends on the environment!

`isdef(name,'local')` returns `%T` if the variable named `name` exists in the local environment of the current function and `%F` otherwise.

`isdef(name,'nolocal')` returns `%T` if the variable named `name` exists in the full calling environment (including the global level) of the current function and `%F` otherwise.

## Examples

    A=1;
    isdef('A')
    clear A
    isdef('A')

    function level1()
      function level2()
        disp(isdef("a","all"));
        disp(isdef("a","local"));
        disp(isdef("a","nolocal"));
      endfunction
      level2()
    endfunction
    function go()
      a=1;
      level1()
    endfunction
    go()

## See Also

- exists
- isglobal
- whereis
- type
- typeof
- clear