lambda_curried_adder.chr

:- module(lambda_curried_adder, [t/2, type(tags/0)]).
:- use_module(prelude).
:- chr_constraint t/2.
:- chr_type tags ---> both ; reuse ; twice_then_add.

:- function make_adder/1, twice/1.

make_adder(N) -> fun(X) -> X + N end.
twice(N)      -> fun(X) -> X + X + N end.

% Two captures coexist; both retain independent N.
t(both, R) <=>
    F1 is make_adder(10),
    F2 is make_adder(20),
    R1 is '$call'(F1, 5),
    R2 is '$call'(F2, 5),
    R = pair(R1, R2).

% Same lambda used twice; result is sum of two applications.
t(reuse, R) <=>
    F is make_adder(7),
    R1 is '$call'(F, 1),
    R2 is '$call'(F, 100),
    R = pair(R1, R2).

% Two distinct closures from different recipes.
t(twice_then_add, R) <=>
    F1 is twice(3),
    F2 is make_adder(100),
    R1 is '$call'(F1, 4),
    R2 is '$call'(F2, R1),
    R = R2.