The order of the arguments in ProXT predicates is the same as that of
the functions interfaced to them. The return value of a function, if
it exists, always appears as the last argument of the predicate.
Motif functions that return a Boolean value are mapped to ProXT predicates
that succeed or fail depending on whether the Motif function returns
True or False.
There is a general class of C functions that take an array and a count of the elements in the array as arguments. In ProXT, arrays are replaced by Prolog lists and the count argument is dropped.
The table in pxt-exp contains all of the built-in predicates in ProXT with their arguments and types.