shithub: pprolog

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Handle the 'unknown' prolog flag correctly

--- a/eval.c

+++ b/eval.c

@@ -40,8 +40,32 @@

 		}else{

 			Predicate *pred = findpredicate(module->predicates, goal);

 			if(pred == nil){

-				print("No predicate matches: %S:%S\n", module->name, prettyprint(goal, 0, 0, 0, nil));

-				goto Backtrack;

+				Rune *name;

+				int arity;

+				Term *replacement = nil;

+				Term *procedure;

+				Term *pi;

+				if(goal->tag == CompoundTerm){

+					name = goal->text;

+					arity = goal->arity;

+				}else{

+					name = prettyprint(goal, 0, 0, 0, nil);

+					arity = 0;

+				}

+				switch(flagunknown){

+				case UnknownError:

+					procedure = mkatom(name);

+					procedure->next = mkinteger(arity);

+					pi = mkcompound(L"/", 2, procedure);

+					replacement = existenceerror(L"procedure", pi);

+					break;

+				case UnknownWarning:

+					print("Warning: no such predicate in module %S: %S/%d\n", module->name, name, arity);

+				case UnknownFail:

+					replacement = mkatom(L"fail");

+				}

+				goalstack = addgoals(goalstack, replacement, module);

+				continue;

 			}

 			/* Find a clause where the head unifies with the goal */