respect the depth in the exhaustive generator

src/runtime/c/pgf/generator.cxx

@@ -391,10 +391,11 @@ void PgfExhaustiveGenerator::predict_literal(ref<PgfText> cat, Result *res)
         return;
     }
 
-    res->exprs.push_back(std::pair<PgfExpr,prob_t>(expr,0));
+    ExprInstance p(expr,0,1);
+    res->exprs.push_back(p);
 
     for (State1 *state : res->states) {
-        state->combine(this,res->scope,expr,0);
+        state->combine(this,res->scope,p);
     }
 }
 
@@ -438,6 +439,7 @@ bool PgfExhaustiveGenerator::State0::process(PgfExhaustiveGenerator *gen)
     state->type   = fun->type;
     state->n_args = 0;
     state->expr   = expr;
+    state->depth  = 1;
 
     if (state->process(gen)) {
         State::release(state,gen->u);
@@ -520,18 +522,22 @@ again:  {
         // predict global functions
         gen->push_left_states(gen->pgf->abstract.funs_by_cat, g.first, arg_res, outside_prob);
     } else {
-        for (std::pair<PgfExpr,prob_t> p : arg_res->exprs) {
-            this->combine(gen,arg_res->scope,p.first,p.second);
+        for (ExprInstance p : arg_res->exprs) {
+            this->combine(gen,arg_res->scope,p);
         }
     }
 
     return false;
 }
 
-void PgfExhaustiveGenerator::State1::combine(PgfExhaustiveGenerator *gen, 
-                                             Scope *scope, PgfExpr expr, prob_t prob)
+void PgfExhaustiveGenerator::State1::combine(PgfExhaustiveGenerator *gen,
+                                             Scope *scope, ExprInstance &p)
 {
+    if (p.depth+1 > gen->depth)
+        return;
+
     Scope *s = scope;
+    PgfExpr expr = p.expr;
     while (s != res->scope) {
         PgfExpr abs = gen->u->eabs(s->bind_type, &s->var, expr);
         if (s != scope) {
@@ -564,10 +570,11 @@ void PgfExhaustiveGenerator::State1::combine(PgfExhaustiveGenerator *gen,
 
     State1 *app_state = new State1();
     app_state->res    = res;
-    app_state->prob   = this->prob + prob;
+    app_state->prob   = this->prob + p.prob;
     app_state->type   = type;
     app_state->n_args = n_args+1;
     app_state->expr   = app;
+    app_state->depth  = std::max(this->depth,p.depth+1);
     gen->queue.push(app_state);
 }
 
@@ -580,9 +587,10 @@ void PgfExhaustiveGenerator::State1::complete(PgfExhaustiveGenerator *gen)
         outside_prob = res->states[0]->prob;
 
     prob_t inside_prob = prob-outside_prob;
-    res->exprs.push_back(std::pair<PgfExpr,prob_t>(expr,inside_prob));
+    ExprInstance p(expr,inside_prob,depth);
+    res->exprs.push_back(p);
     for (State1 *state : res->states) {
-        state->combine(gen,res->scope,expr,inside_prob);
+        state->combine(gen,res->scope,p);
     }
 }
 
@@ -601,8 +609,8 @@ PgfExpr PgfExhaustiveGenerator::fetch(PgfDB *db, prob_t *prob)
     for (;;) {
         if (top_res_index < top_res->exprs.size()) {
             auto pair = top_res->exprs[top_res_index++];
-            *prob = pair.second;
-            return pair.first;
+            *prob = pair.prob;
+            return pair.expr;
         }
 
         if (queue.empty())
@@ -626,7 +634,7 @@ PgfExhaustiveGenerator::~PgfExhaustiveGenerator()
 
     for (auto i : results) {
         for (auto j : i.second->exprs) {
-            free_ref(j.first);
+            free_ref(j.expr);
         }
     }
 

src/runtime/c/pgf/generator.h

@@ -100,15 +100,28 @@ class PGF_INTERNAL_DECL PgfExhaustiveGenerator : public PgfGenerator, public Pgf
         virtual bool process(PgfExhaustiveGenerator *gen);
     };
 
+    struct ExprInstance {
+        PgfExpr expr;
+        prob_t prob;
+        size_t depth;
+
+        ExprInstance(PgfExpr expr, prob_t prob, size_t depth) {
+            this->expr = expr;
+            this->prob = prob;
+            this->depth = depth;
+        }
+    };
+
     struct State1 : State {
         ref<PgfDTyp> type;
         size_t n_args;
         PgfExpr expr;
+        size_t depth;
 
         virtual bool process(PgfExhaustiveGenerator *gen);
         virtual void free_refs(PgfUnmarshaller *u);
         void combine(PgfExhaustiveGenerator *gen, 
-                     Scope *scope, PgfExpr expr, prob_t prob);
+                     Scope *scope, ExprInstance &p);
         void complete(PgfExhaustiveGenerator *gen);
     };
 
@@ -119,7 +132,7 @@ class PGF_INTERNAL_DECL PgfExhaustiveGenerator : public PgfGenerator, public Pgf
         Scope *scope;
         size_t scope_len;
         std::vector<State1*> states;
-        std::vector<std::pair<PgfExpr,prob_t>> exprs;
+        std::vector<ExprInstance> exprs;
 
         Result() {
             this->ref_count = 0;