quote_in_unify.chr

:- module(quote_in_unify, [flat/1, nested/1]).
:- use_module(prelude).
:- chr_constraint flat/1, nested/1.

% '=' is pure structural unification: neither operand evaluates, and
% the 'quote/1' quoting form is preserved as ordinary compound data
% (same as in head/equation patterns). Regression for the bug where
% the rule-body lowering of '=' stripped quote/1 while the REPL did
% not.

flat(R) <=> R = quote(plus(2, 3)).

nested(R) <=> R = quote(quote(plus(2, 3))).