funref_bounded_satisfied.chr

:- module(funref_bounded_satisfied, [c/1]).
:- use_module(library(prelude)).

:- chr_constraint c(any).

:- function gt(int, int) -> bool.
gt(X, Y) -> X > Y.

:- function mymax(T, T) -> T requiring gt(T, T) -> bool.
mymax(X, Y) | gt(X, Y) -> X.
mymax(_, Y) -> Y.

:- function apply2(fun(A, A) -> A end, A, A) -> A.
apply2(F, X, Y) -> '$call'(F, X, Y).

% Bound satisfied via a function reference: A := int, and
% gt(int, int) -> bool is declared, so the bound discharges silently.
c(R) <=> R is apply2(fun mymax/2, 1, 2).