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\DOC applyd
\TYPE {applyd : ('a, 'b) func -> ('a -> 'b) -> 'a -> 'b}
\SYNOPSIS
Applies a finite partial function, with a backup function for undefined points.
\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. If {f} is a finite partial function, {g} a conventional function and {x}
an argument, {tryapply f g x} tries to apply {f} to {x} as with {apply f x},
but instead returns {g x} is {f} is undefined on {x}.
\FAILURE
Can only fail if the backup function fails.
\EXAMPLE
{
# applyd undefined (fun x -> x) 1;;
val it : int = 1
# applyd (1 |=> 2) (fun x -> x) 1;;
val it : int = 2
}
\SEEALSO
|->, |=>, apply, choose, combine, defined, dom, foldl, foldr,
graph, is_undefined, mapf, ran, tryapplyd, undefine, undefined.
\ENDDOC
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