From 44ab8a339c78bcc3460d44b2f435116f21faa60a Mon Sep 17 00:00:00 2001
From: Peter Mikkelsen <peter@pmikkelsen.com>
Date: Mon, 5 Jul 2021 16:27:38 +0000
Subject: First step on modules. Still very very rough.

---
 eval.c | 72 +++++++++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 45 insertions(+), 27 deletions(-)

(limited to 'eval.c')

diff --git a/eval.c b/eval.c
index dea8b2b..a7f2c43 100644
--- a/eval.c
+++ b/eval.c
@@ -6,7 +6,7 @@
 #include "fns.h"
 
 Goal *addgoals(Goal *, Term *);
-Term *findclause(Term *, Term *, Binding **);
+Clause *findclause(Clause *, Term *, Binding **);
 int equalterms(Term *, Term *);
 Goal *copygoals(Goal *);
 Builtin findbuiltin(Term *);
@@ -14,8 +14,9 @@ Builtin findbuiltin(Term *);
 static uvlong clausenr;
 
 int
-evalquery(Term *database, Term *query, Binding **resultbindings)
+evalquery(Term *query, Binding **resultbindings)
 {
+	static Module *currentmodule = nil;
 	if(choicestack == nil){
 	/*
 		The goal stack has the original query at the very bottom, protected by a catch frame where the ->goal field is nil.
@@ -37,42 +38,60 @@ evalquery(Term *database, Term *query, Binding **resultbindings)
 		goalstack = addgoals(goalstack, query);
 
 		clausenr = 2; /* Start at two since 0 is for the facts in the database, and 1 is for queries */
+
+		currentmodule = usermodule;
 	}else{
 		goto Backtrack;
 	}
 
 	while(goalstack->goal != nil){
-		Term *dbstart;
+		Clause *startclause;
 		Term *goal;
 		Goal *oldgoalstack;
 
-		dbstart = database;
+		startclause = nil; /* Where to start looking for a matching clause. Used by backtracking */
 Retry:
-		print("Loop run\n");
 		goal = goalstack->goal;
 		oldgoalstack = goalstack;
 		goalstack = goalstack->next;
 
-		if(oldgoalstack->catcher){
-			print("Was catchframe\n");
+		if(oldgoalstack->catcher)
 			continue;
-		}
 
 		if(debug)
 			print("Working goal: %S\n", prettyprint(goal, 0, 0, 0));
 
+		if(startclause == nil && goal->tag == CompoundTerm && goal->arity == 2 && runestrcmp(goal->text, L":") == 0){
+			Term *module = goal->children;
+			if(module->tag == AtomTerm){
+				Module *m = getmodule(module->text);
+				if(m == nil)
+					goal = existenceerror(L"module", module);
+				else{
+					goal = module->next;
+					currentmodule = m;
+					startclause = m->clauses;
+					oldgoalstack->goal = goal;
+				}
+			}else
+				goal = typeerror(L"module", module);
+		}
+
+		if(startclause == nil)
+			startclause = currentmodule->clauses;
+
 		Binding *bindings = nil;
-		Term *clause = nil;
+		Clause *clause = nil;
 		
 		/* Try to see if the goal can be solved using a builtin first */
 		Builtin builtin = findbuiltin(goal);
 		if(builtin != nil){
-			int success = builtin(database, goal, &bindings);
+			int success = builtin(goal, &bindings);
 			if(!success)
 				goto Backtrack;
 		}else{
 			/* Find a clause where the head unifies with the goal */
-			clause = findclause(dbstart, goal, &bindings);
+			clause = findclause(startclause, goal, &bindings);
 			if(clause != nil){
 				if(clause->next != nil){
 					/* Add a choicepoint. Note we create a choicepoint every time, so there is room for improvement. */
@@ -81,6 +100,7 @@ Retry:
 					cp->next = choicestack;
 					cp->retryclause = clause->next;
 					cp->id = clause->clausenr;
+					cp->currentmodule = currentmodule;
 					choicestack = cp;
 				}
 			}else{
@@ -93,7 +113,8 @@ Backtrack:
 				choicestack = cp->next;
 				/* freegoals(goals) */
 				goalstack = cp->goalstack;
-				dbstart = cp->retryclause;
+				currentmodule = cp->currentmodule;
+				startclause = cp->retryclause;
 				goto Retry;
 			}
 		}
@@ -106,8 +127,8 @@ Backtrack:
 		}
 
 		/* Add clause body as goals, with bindings applied */
-		if(clause != nil && clause->tag == CompoundTerm && clause->arity == 2 && runestrcmp(clause->text, L":-") == 0){
-			Term *subgoal = copyterm(clause->children->next, nil);
+		if(clause != nil && clause->body != nil){
+			Term *subgoal = copyterm(clause->body, nil);
 			applybinding(subgoal, bindings);
 			goalstack = addgoals(goalstack, subgoal);
 		}
@@ -133,21 +154,18 @@ addgoals(Goal *goals, Term *t)
 	return goals;
 }
 
-Term *
-findclause(Term *database, Term *goal, Binding **bindings)
+Clause *
+findclause(Clause *clauses, Term *goal, Binding **bindings)
 {
-	Term *clause;
-	Term *head;
-	for(; database != nil; database = database->next){
-		clause = copyterm(database, &clausenr);
-		clausenr++;
-		clause->next = database->next;
-		if(clause->tag == CompoundTerm && runestrcmp(clause->text, L":-") == 0 && clause->arity == 2)
-			head = clause->children;
-		else
-			head = clause;
+	Clause *clause;
+	for(; clauses != nil; clauses = clauses->next){
+		if(!clauses->public)
+			continue;
 
-		if(unify(head, goal, bindings))
+		clause = copyclause(clauses, &clausenr);
+		clausenr++;
+		clause->next = clauses->next;
+		if(unify(clause->head, goal, bindings))
 			return clause;
 	}
 	return nil;
-- 
cgit v1.2.3