4 files changed, 171 insertions, 6 deletions

diff --git a/src/runtime/c/Makefile.am b/src/runtime/c/Makefile.am
index f6e8a263a..cfb7461df 100644
--- a/src/runtime/c/Makefile.am
+++ b/src/runtime/c/Makefile.am
@@ -111,6 +111,7 @@ libpgf_la_SOURCES = \
 	pgf/reader.h \
 	pgf/reader.c \
 	pgf/linearize.c \
+	pgf/reasoner.c \
 	pgf/printer.c \
 	pgf/pgf.c \
 	pgf/pgf.h
diff --git a/src/runtime/c/pgf/parser.h b/src/runtime/c/pgf/parser.h
index dcc3ca3af..6952d33ab 100644
--- a/src/runtime/c/pgf/parser.h
+++ b/src/runtime/c/pgf/parser.h
@@ -82,11 +82,6 @@ pgf_parser_add_literal(PgfConcr *concr, PgfCId cat,
  * @{
  */
 
-
-/// An enumeration of #PgfExpr elements.
-typedef GuEnum PgfExprEnum;
-
-
 /// Retrieve the current parses from the parse state.
 PgfExprEnum*
 pgf_parse_result(PgfParseState* state, GuPool* pool);
diff --git a/src/runtime/c/pgf/pgf.h b/src/runtime/c/pgf/pgf.h
index 9963534b5..1f3947bff 100644
--- a/src/runtime/c/pgf/pgf.h
+++ b/src/runtime/c/pgf/pgf.h
@@ -54,6 +54,9 @@ extern GU_DECLARE_TYPE(PgfConcr, struct);
 #include <pgf/expr.h>
 #include <pgf/lexer.h>
 
+/// An enumeration of #PgfExpr elements.
+typedef GuEnum PgfExprEnum;
+
 PgfPGF*
 pgf_read(const char* fpath,
          GuPool* pool, GuExn* err);
@@ -109,9 +112,12 @@ pgf_print_name(PgfConcr*, PgfCId id);
 void
 pgf_linearize(PgfConcr* concr, PgfExpr expr, GuWriter* wtr, GuExn* err);
 
-GuEnum*
+PgfExprEnum*
 pgf_parse(PgfConcr* concr, PgfCId cat, PgfLexer *lexer, GuPool* pool);
 
+PgfExprEnum*
+pgf_generate(PgfPGF* pgf, PgfCId cat, GuPool* pool);
+
 // an experimental function. Please don't use it
 void
 pgf_print_chunks(PgfConcr* concr, PgfCId cat, PgfLexer *lexer, GuPool* pool);
diff --git a/src/runtime/c/pgf/reasoner.c b/src/runtime/c/pgf/reasoner.c
new file mode 100644
index 000000000..9a15bded7
--- /dev/null
+++ b/src/runtime/c/pgf/reasoner.c
@@ -0,0 +1,163 @@
+#include <pgf/pgf.h>
+#include <pgf/data.h>
+#include <math.h>
+#include <stdio.h>
+
+typedef struct PgfExprState PgfExprState;
+
+struct PgfExprState {
+	PgfExprState* cont;
+	PgfExpr expr;
+	PgfHypos hypos;
+	size_t arg_idx;
+};
+
+typedef struct {
+	PgfExprState *st;
+	prob_t cont_prob;
+	size_t fun_idx;
+	PgfCat* abscat;
+} PgfExprQState;
+
+typedef struct {
+	GuPool* tmp_pool;
+	PgfAbstr* abstract;
+	GuBuf* pqueue;
+	PgfExprEnum en;
+} PgfReasoner;
+
+static int
+cmp_expr_qstate(GuOrder* self, const void* a, const void* b)
+{
+	PgfExprQState *q1 = (PgfExprQState *) a;
+	PgfExprQState *q2 = (PgfExprQState *) b;
+
+	prob_t prob1 = q1->cont_prob-log(q1->abscat->functions[q1->fun_idx].prob);
+	prob_t prob2 = q2->cont_prob-log(q2->abscat->functions[q2->fun_idx].prob);
+	
+	if (prob1 < prob2)
+		return -1;
+	else if (prob1 > prob2)
+		return 1;
+	else
+		return 0;
+}
+
+static GuOrder
+pgf_expr_qstate_order = { cmp_expr_qstate };
+
+static bool
+pgf_reasoner_cat_init(PgfReasoner* rs, 
+                      PgfExprState* cont, prob_t cont_prob, PgfCId cat,
+                      GuPool* pool)
+{
+	// Checking for loops in the chart
+	if (cont != NULL) {
+		PgfExprState* st = cont->cont;
+		while (st != NULL) {
+			PgfHypo* hypo = gu_seq_index(st->hypos, PgfHypo, st->arg_idx);
+			if (gu_string_eq(hypo->type->cid, cat))
+				return false;
+
+			st = st->cont;
+		}
+	}
+
+	PgfCat* abscat = gu_map_get(rs->abstract->cats, &cat, PgfCat*);
+	if (abscat == NULL) {
+		return false;
+	}
+
+	PgfExprQState q = {cont, cont_prob, 0, abscat};
+	gu_buf_heap_push(rs->pqueue, &pgf_expr_qstate_order, &q);	
+	return true;
+}
+
+static PgfExprProb*
+pgf_reasoner_next(PgfReasoner* rs, GuPool* pool)
+{
+	if (rs->pqueue == NULL)
+		return NULL;
+
+	while (gu_buf_length(rs->pqueue) > 0) {
+		PgfExprQState q;
+		gu_buf_heap_pop(rs->pqueue, &pgf_expr_qstate_order, &q);
+
+		PgfCId fun = q.abscat->functions[q.fun_idx++].fun;
+		PgfFunDecl* absfun =
+			gu_map_get(rs->abstract->funs, &fun, PgfFunDecl*);
+
+		if (q.fun_idx < q.abscat->n_functions) {
+			gu_buf_heap_push(rs->pqueue, &pgf_expr_qstate_order, &q);
+		}
+
+		if (absfun == NULL)
+			continue;
+
+		PgfExprState *st = gu_new(PgfExprState, rs->tmp_pool);
+		st->cont = q.st;
+		st->expr =
+			gu_new_variant_i(pool, PGF_EXPR_FUN,
+							 PgfExprFun,
+							 .fun = fun);
+		st->hypos = absfun->type->hypos;
+		st->arg_idx = 0;
+
+		for (;;) {
+			prob_t prob = q.cont_prob+absfun->ep.prob;
+
+			if (st->arg_idx < gu_seq_length(st->hypos)) {
+				PgfHypo *hypo = gu_seq_index(st->hypos, PgfHypo, st->arg_idx);
+				pgf_reasoner_cat_init(rs, st, prob,
+									  hypo->type->cid, pool);
+				break;
+			} else {
+				PgfExprState* cont = st->cont;
+				if (cont == NULL) {
+					PgfExprProb* ep = gu_new(PgfExprProb, pool);
+					ep->expr = st->expr;
+					ep->prob = prob;
+					return ep;
+				}
+
+				st->cont = cont->cont;
+				st->expr =
+					gu_new_variant_i(pool, PGF_EXPR_APP,
+							PgfExprApp,
+							.fun = cont->expr, .arg = st->expr);
+				st->hypos = cont->hypos;
+				st->arg_idx = cont->arg_idx+1;
+			}
+		}
+	}
+
+	gu_pool_free(rs->tmp_pool);
+	rs->tmp_pool = NULL;
+	rs->pqueue = NULL;
+	return NULL;
+}
+
+static void
+pgf_reasoner_enum_next(GuEnum* self, void* to, GuPool* pool)
+{
+	PgfReasoner* pr = gu_container(self, PgfReasoner, en);
+	*(PgfExprProb**)to = pgf_reasoner_next(pr, pool);
+}
+
+PgfExprEnum*
+pgf_generate(PgfPGF* pgf, PgfCId cat, GuPool* pool)
+{
+	GuPool* tmp_pool = gu_new_pool();
+	GuBuf* pqueue = gu_new_buf(PgfExprQState, tmp_pool);
+
+	PgfReasoner* rs =
+           gu_new_i(pool, PgfReasoner,
+			 .tmp_pool = tmp_pool,
+             .abstract = &pgf->abstract,
+			 .pqueue = pqueue,
+			 .en.next = pgf_reasoner_enum_next);
+
+	pgf_reasoner_cat_init(rs, NULL, 0, cat, pool);
+
+	return &rs->en;
+}