Is a Symbol Bound?

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Is a Symbol Bound?

Syntax

exists(x, envir=null, mode="any", inherits=false)

Arguments

`x`	a symbol (given as a quoted string).
`envir`	an environent to be searched.
`mode`	the type of interest for the object.
`inherits`	should the enclosing frames of the environment be inspected.

Description

exists looks to see if the symbol x has a value bound to it.
If envir is null then the the currently active environment
is searched first.
If inherits is true and a value is not found for x,
then the parent frames of envir are searched until the symbol
x is encountered. 
If mode is specified then only objects of that mode are searched for.
exists returns true if the symbol is encountered and
false if not.