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\DOC tryapplyd
\TYPE {tryapplyd : ('a, 'b) func -> 'a -> 'b -> 'b}
\SYNOPSIS
Applies a finite partial function, with a default 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, {x} an element of its domain type and
{y} of its range type, the call {tryapplyd f x y} tries to apply {f} to the
value {x}, as with {apply f x}, but if it is undefined, simply returns {y}
\FAILURE
Never fails.
\EXAMPLE
{
# tryapplyd (1 |=> 2) 1 (-1);;
val it : int = 2
# tryapplyd undefined 1 (-1);;
val it : int = -1
}
\SEEALSO
|->, |=>, apply, applyd, choose, combine, defined, dom, foldl, foldr,
graph, is_undefined, mapf, ran, undefine, undefined.
\ENDDOC
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