Applies a finite partial function, with a default for undefined points.
DESCRIPTION
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 CONDITIONS
Never fails.
EXAMPLE
# tryapplyd (1 |=> 2) 1 (-1);;
val it : int = 2
# tryapplyd undefined 1 (-1);;
val it : int = -1