:- initialization(main). % A toplevel answer reports an answer substitution, so every equation % in an answer description binds a variable. '1 = X' does not, and is % consumed as a malformed description rather than loaded as a clause. % The load carries on and run_quads reports it as failed (issue #1078). ?- X = 1. 1 = X. main :- use_module(library(quads)), run_quads.