hnf_literal_in_head.chr

:- module(hnf_literal_in_head, [tag/2, type(pat/0)]).
:- chr_constraint tag/2.
:- chr_type pat ---> foo ; bar ; p(any, any) ; a ; b ; c.

% Literal head args of every kind: int, float, atom, string, empty list, compound.
tag(0, R)         <=> R = zero.
tag(42, R)        <=> R = answer.
tag(1.5, R)       <=> R = one_half.
tag(0.0, R)       <=> R = float_zero.
tag(foo, R)       <=> R = foo_atom.
tag("hi", R)      <=> R = hi_string.
tag([], R)        <=> R = empty_list.
tag(p(a, b), R)   <=> R = pair_ab.
tag(_, R)         <=> R = catchall.