diff --git a/src/runtime/c/pgf/namespace.h b/src/runtime/c/pgf/namespace.h
index dfbd999b4..17715bac2 100644
--- a/src/runtime/c/pgf/namespace.h
+++ b/src/runtime/c/pgf/namespace.h
@@ -658,7 +658,7 @@ void namespace_iter_prefix(Namespace<V> map, PgfText *prefix, PgfItor* itor, Pgf
 }
 
 template <class V>
-Namespace<V> namespace_map(Namespace<V> map, std::function<ref<V>(ref<V>)> f)
+Namespace<V> namespace_map(Namespace<V> map, std::function<ref<V>(ref<V>)> &f)
 {
     if (map != 0) {
         auto left  = namespace_map(map->left, f);
diff --git a/src/runtime/c/pgf/pgf.cxx b/src/runtime/c/pgf/pgf.cxx
index 3234358af..55c5c6978 100644
--- a/src/runtime/c/pgf/pgf.cxx
+++ b/src/runtime/c/pgf/pgf.cxx
@@ -510,7 +510,12 @@ void pgf_iter_functions_by_cat(PgfDB *db, PgfRevision revision,
         DB_scope scope(db, READER_SCOPE);
         ref<PgfPGF> pgf = db->revision2pgf(revision);
 
-        probspace_iter(pgf->abstract.funs_by_cat, cat, itor, false, err);
+        std::function<bool(ref<PgfAbsFun>)> f =
+            [itor,err](ref<PgfAbsFun> fun) {
+                itor->fn(itor, &fun->name, fun.as_object(), err);
+                return (err->type == PGF_EXN_NONE);
+            };
+        probspace_iter(pgf->abstract.funs_by_cat, cat, f, false);
     } PGF_API_END
 }
 
@@ -2239,13 +2244,6 @@ void pgf_create_lincat(PgfDB *db,
     } PGF_API_END
 }
 
-static
-void iter_drop_lincat_helper(PgfItor *itor, PgfText *key, object value, PgfExn *err)
-{
-    ref<PgfConcr> concr = ((PgfDropItor*) itor)->concrete;
-    drop_lin(concr, key);
-}
-
 PGF_API
 void pgf_drop_lincat(PgfDB *db,
                      PgfRevision revision,PgfConcrRevision cnc_revision,
@@ -2265,13 +2263,12 @@ void pgf_drop_lincat(PgfDB *db,
 
             // Remove the linearizations of all functions that
             // depend on it.
-            PgfDropItor itor;
-            itor.fn       = iter_drop_lincat_helper;
-            itor.pgf      = pgf;
-            itor.concrete = concr;
-            itor.name     = name;
-            probspace_iter(pgf->abstract.funs_by_cat, name,
-                           &itor, true, err);
+            std::function<bool(ref<PgfAbsFun>)> f =
+                [concr](ref<PgfAbsFun> fun) {
+                    drop_lin(concr, &fun->name);
+                    return true;
+                };
+            probspace_iter(pgf->abstract.funs_by_cat, name, f, true);
 
             // Remove the sequences comprizing the lindef and linref
             object container = lincat.tagged();
diff --git a/src/runtime/c/pgf/probspace.cxx b/src/runtime/c/pgf/probspace.cxx
index 848b7212b..78bc107e0 100644
--- a/src/runtime/c/pgf/probspace.cxx
+++ b/src/runtime/c/pgf/probspace.cxx
@@ -172,35 +172,27 @@ PgfProbspace probspace_delete_by_cat(PgfProbspace space, PgfText *cat,
     }
 }
 
-void probspace_iter(PgfProbspace space, PgfText *cat,
-                    PgfItor* itor, bool all, PgfExn *err)
+bool probspace_iter(PgfProbspace space, PgfText *cat,
+                    std::function<bool(ref<PgfAbsFun>)> &f, bool all)
 {
     if (space == 0)
-        return;
+        return true;
 
     int cmp = textcmp(cat,&(*space->value.cat));
     if (cmp < 0) {
-        probspace_iter(space->left, cat, itor, all, err);
-        if (err->type != PGF_EXN_NONE)
-            return;
+        return probspace_iter(space->left, cat, f, all);
     } else if (cmp > 0) {
-        probspace_iter(space->right, cat, itor, all, err);
-        if (err->type != PGF_EXN_NONE)
-            return;
+        return probspace_iter(space->right, cat, f, all);
     } else {
-        probspace_iter(space->left, cat, itor, all, err);
-        if (err->type != PGF_EXN_NONE)
-            return;
+        if (!probspace_iter(space->left, cat, f, all))
+            return false;
 
         if (all || space->value.is_result()) {
-            itor->fn(itor, &space->value.fun->name, space->value.fun.as_object(), err);
-            if (err->type != PGF_EXN_NONE)
-                return;
+            if (!f(space->value.fun))
+                return false;
         }
 
-        probspace_iter(space->right, cat, itor, all, err);
-        if (err->type != PGF_EXN_NONE)
-            return;
+        return probspace_iter(space->right, cat, f, all);
     }
 }
 
diff --git a/src/runtime/c/pgf/probspace.h b/src/runtime/c/pgf/probspace.h
index 714a00720..e67f5a7d2 100644
--- a/src/runtime/c/pgf/probspace.h
+++ b/src/runtime/c/pgf/probspace.h
@@ -66,8 +66,8 @@ PgfProbspace probspace_delete_by_cat(PgfProbspace space, PgfText *cat,
                                      PgfItor* itor, PgfExn *err);
 
 PGF_INTERNAL_DECL
-void probspace_iter(PgfProbspace space, PgfText *cat,
-                    PgfItor* itor, bool all, PgfExn *err);
+bool probspace_iter(PgfProbspace space, PgfText *cat,
+                    std::function<bool(ref<PgfAbsFun>)> &f, bool all);
 
 /* Given a random number from 0 to 1, select a random function from
  * the given category */