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\DOC defined
\TYPE {defined : ('a, 'b) func -> 'a -> bool}
\SYNOPSIS
Tests if a finite partial function is defined on a certain domain value.
\DESCRIBE
This is one of a suite of operations on finite partial functions, type
{('a,'b)func}. These may sometimes be preferable to ordinary functions since
they permit more operations such as equality comparison, extraction of domain
etc. The call {defined f x} returns {true} if the finite partial function {f}
is defined on domain value {x}, and {false} otherwise.
\FAILURE
Never fails.
\EXAMPLE
{
# defined (1 |=> 2) 1;;
val it : bool = true
# defined (1 |=> 2) 2;;
val it : bool = false
# defined undefined 1;;
val it : bool = false
}
\SEEALSO
|->, |=>, apply, applyd, choose, combine, defined, dom, foldl, foldr,
graph, is_undefined, mapf, ran, tryapplyd, undefined.
\ENDDOC
|
