Merge remote-tracking branch 'origin/master' into fix-newer-cabal

2026-05-06 09:42:50 -06:00 · 2020-09-05 21:11:12 +02:00
parent 57ce76dbc1 bca0691cb0
commit 56f94da772
12 changed files with 264 additions and 133 deletions
--- a/bin/template.html
+++ b/bin/template.html
@@ -82,9 +82,10 @@ $body$
          <li><a href="http://cloud.grammaticalframework.org/">GF Cloud</a></li>
          <li>
            <a href="$rel-root$/doc/tutorial/gf-tutorial.html">Tutorial</a>
-            /
+             ·
            <a href="$rel-root$/lib/doc/rgl-tutorial/index.html">RGL Tutorial</a>
          </li>
+          <li><a href="$rel-root$/doc/gf-video-tutorials.html">Video Tutorials</a></li>
          <li><a href="$rel-root$/download"><strong>Download GF</strong></a></li>
        </ul>
      </div>
--- a/doc/gf-video-tutorials.md
+++ b/doc/gf-video-tutorials.md
@@ -0,0 +1,35 @@
+---
+title: "Video tutorials"
+---
+
+The GF [YouTube channel](https://www.youtube.com/channel/UCZ96DechSUVcXAhtOId9VVA) keeps a playlist of [all GF videos](https://www.youtube.com/playlist?list=PLrgqBB5thLeT15fUtJ8_Dtk8ppdtH90MK), and more specific playlists for narrower topics.
+If you make a video about GF, let us know and we'll add it to the suitable playlist(s)!
+
+- [General introduction to GF](#general-introduction-to-gf)
+- [Beginner resources](#beginner-resources)
+- [Resource grammar tutorials](#resource-grammar-tutorials)
+
+## General introduction to GF
+
+These videos introduce GF at a high level, and present some use cases.
+
+__Grammatical Framework: Formalizing the Grammars of the World__
+
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/x1LFbDQhbso" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+__Aarne Ranta: Automatic Translation for Consumers and Producers__
+
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/An-AmFScw1o" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+## Beginner resources
+
+These videos show how to install GF on your computer (Mac or Windows), and how to play with simple grammars in a [Jupyter notebook](https://github.com/GrammaticalFramework/gf-binder) (any platform, hosted at [mybinder.org](https://mybinder.org)).
+
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/videoseries?list=PLrgqBB5thLeRa8eViJJnjT8jBhxqCPMF2" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+## Resource grammar tutorials
+
+These videos show incremental improvements to a [miniature version of the resource grammar](https://github.com/inariksit/comp-syntax-2020/tree/master/lab2/grammar/dummy#readme).
+They assume some prior knowledge of GF, roughly lessons 1-3 from the [GF tutorial](http://www.grammaticalframework.org/doc/tutorial/gf-tutorial.html).
+
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/videoseries?list=PLrgqBB5thLeTPkp88lnOmRtprCa8g0wX2" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
--- a/doc/tutorial/gf-tutorial.t2t
+++ b/doc/tutorial/gf-tutorial.t2t
@@ -898,7 +898,7 @@ Parentheses are only needed for grouping.
 Parsing something that is not in grammar will fail:
 ```
  > parse "hello dad"
-  Unknown words: dad
+  The parser failed at token 2: "dad"

  > parse "world hello"
  no tree found
@@ -2948,7 +2948,7 @@ We need the following combinations:
 ```
 We also need **lexical insertion**, to form phrases from single words:
 ```
-  mkCN : N -> NP ;
+  mkCN : N -> CN ;
  mkAP : A -> AP ;
 ```
 Naming convention: to construct a //C//, use a function ``mk``//C//.
@@ -2969,7 +2969,7 @@ can be built as follows:
 ```
  mkCl
    (mkNP these_Det
-       (mkCN (mkAP very_AdA (mkAP warm_A)) (mkCN pizza_CN)))
+       (mkCN (mkAP very_AdA (mkAP warm_A)) (mkCN pizza_N)))
    (mkAP italian_AP)
 ```
 The task now: to define the concrete syntax of ``Foods`` so that
@@ -4200,6 +4200,7 @@ We construct a calculator with addition, subtraction, multiplication, and
 division of integers.
 ```
  abstract Calculator = {
+  flags startcat = Exp ;
  
  cat Exp ;

@@ -4226,7 +4227,7 @@ We begin with a
 concrete syntax that always uses parentheses around binary
 operator applications:
 ```
-  concrete CalculatorP of Calculator = {
+  concrete CalculatorP of Calculator = open Prelude in {

  lincat
    Exp = SS ;
--- a/index.html
+++ b/index.html
@@ -39,7 +39,7 @@
        /
        <a href="lib/doc/rgl-tutorial/index.html">RGL Tutorial</a>
      </li>
-      <li><a href="https://www.youtube.com/playlist?list=PL4L18Hhub0qFgLgFmzE4h-FxqemBcvWSW">Video Tutorial</a></li>
+      <li><a href="doc/gf-video-tutorials.html">Video Tutorials</a></li>
    </ul>

    <a href="download/index.html" class="btn btn-primary ml-3">
--- a/src/compiler/GF/Compile/PGFtoHaskell.hs
+++ b/src/compiler/GF/Compile/PGFtoHaskell.hs
@@ -26,6 +26,7 @@ import Data.List --(isPrefixOf, find, intersperse)
 import qualified Data.Map as Map

 type Prefix = String -> String
+type DerivingClause = String

 -- | the main function
 grammar2haskell :: Options
@@ -33,29 +34,36 @@ grammar2haskell :: Options
                -> PGF
                -> String
 grammar2haskell opts name gr = foldr (++++) [] $
-  pragmas ++ haskPreamble gadt name ++ [types, gfinstances gId lexical gr'] ++ compos
+  pragmas ++ haskPreamble gadt name derivingClause extraImports ++
+  [types, gfinstances gId lexical gr'] ++ compos
    where gr' = hSkeleton gr
          gadt = haskellOption opts HaskellGADT
+          dataExt = haskellOption opts HaskellData
          lexical cat = haskellOption opts HaskellLexical && isLexicalCat opts cat
-          gId | haskellOption opts HaskellNoPrefix = id
-              | otherwise = ("G"++)
-          pragmas | gadt = ["{-# OPTIONS_GHC -fglasgow-exts #-}","{-# LANGUAGE GADTs #-}"]
+          gId | haskellOption opts HaskellNoPrefix = rmForbiddenChars
+              | otherwise = ("G"++) . rmForbiddenChars
+          -- GF grammars allow weird identifier names inside '', e.g. 'VP/Object'
+          rmForbiddenChars = filter (`notElem` "'!#$%&*+./<=>?@\\^|-~")
+          pragmas | gadt = ["{-# LANGUAGE GADTs, FlexibleInstances, KindSignatures, RankNTypes, TypeSynonymInstances #-}"]
+                  | dataExt = ["{-# LANGUAGE DeriveDataTypeable #-}"]
                  | otherwise = []
+          derivingClause
+                 | dataExt = "deriving (Show,Data)"
+                 | otherwise = "deriving Show"
+          extraImports | gadt = ["import Control.Monad.Identity",
+                                 "import Data.Monoid"]
+                       | dataExt = ["import Data.Data"]
+                       | otherwise = []
          types | gadt = datatypesGADT gId lexical gr'
-                | otherwise = datatypes gId lexical gr'
+                | otherwise = datatypes gId derivingClause lexical gr'
          compos | gadt = prCompos gId lexical gr' ++ composClass
                 | otherwise = []

-haskPreamble gadt name =
+haskPreamble gadt name derivingClause extraImports =
 [
  "module " ++ name ++ " where",
  ""
- ] ++
- (if gadt then [
-  "import Control.Monad.Identity",
-  "import Data.Monoid"
-  ] else []) ++
- [
+ ] ++ extraImports ++ [
  "import PGF hiding (Tree)",
  "----------------------------------------------------",
  "-- automatic translation from GF to Haskell",
@@ -65,11 +73,11 @@ haskPreamble gadt name =
  "  gf :: a -> Expr",
  "  fg :: Expr -> a",
  "",
-  predefInst gadt "GString" "String"  "unStr"    "mkStr",
+  predefInst gadt derivingClause "GString" "String"  "unStr"    "mkStr",
  "",
-  predefInst gadt "GInt"    "Int"     "unInt"    "mkInt",
+  predefInst gadt derivingClause "GInt"    "Int"     "unInt"    "mkInt",
  "",
-  predefInst gadt "GFloat"  "Double"  "unFloat"  "mkFloat",
+  predefInst gadt derivingClause "GFloat"  "Double"  "unFloat"  "mkFloat",
  "",
  "----------------------------------------------------",
  "-- below this line machine-generated",
@@ -77,10 +85,10 @@ haskPreamble gadt name =
  ""
 ]

-predefInst gadt gtyp typ destr consr = 
+predefInst gadt derivingClause gtyp typ destr consr =
  (if gadt
    then []
-    else ("newtype" +++ gtyp +++ "=" +++ gtyp +++ typ +++ " deriving Show\n\n") 
+    else ("newtype" +++ gtyp +++ "=" +++ gtyp +++ typ +++ derivingClause ++ "\n\n")
    )
  ++
  "instance Gf" +++ gtyp +++ "where" ++++
@@ -94,24 +102,24 @@ type OIdent = String

 type HSkeleton = [(OIdent, [(OIdent, [OIdent])])]

-datatypes :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> String
-datatypes gId lexical = (foldr (+++++) "") . (filter (/="")) . (map (hDatatype gId lexical)) . snd
+datatypes :: Prefix -> DerivingClause -> (OIdent -> Bool) -> (String,HSkeleton) -> String
+datatypes gId derivingClause lexical = (foldr (+++++) "") . (filter (/="")) . (map (hDatatype gId derivingClause lexical)) . snd

 gfinstances :: Prefix -> (OIdent -> Bool) -> (String,HSkeleton) -> String
 gfinstances gId lexical (m,g) = (foldr (+++++) "") $ (filter (/="")) $ (map (gfInstance gId lexical m)) g


-hDatatype  :: Prefix -> (OIdent -> Bool) -> (OIdent, [(OIdent, [OIdent])]) -> String
-hDatatype _ _ ("Cn",_) = "" ---
-hDatatype gId _ (cat,[]) = "data" +++ gId cat
-hDatatype gId _ (cat,rules) | isListCat (cat,rules) = 
+hDatatype  :: Prefix -> DerivingClause -> (OIdent -> Bool) -> (OIdent, [(OIdent, [OIdent])]) -> String
+hDatatype _ _ _ ("Cn",_) = "" ---
+hDatatype gId _ _ (cat,[]) = "data" +++ gId cat
+hDatatype gId derivingClause _ (cat,rules) | isListCat (cat,rules) =
 "newtype" +++ gId cat +++ "=" +++ gId cat +++ "[" ++ gId (elemCat cat) ++ "]"
-  +++ "deriving Show"
-hDatatype gId lexical (cat,rules) =
+  +++ derivingClause
+hDatatype gId derivingClause lexical (cat,rules) =
 "data" +++ gId cat +++ "=" ++
 (if length rules == 1 then "" else "\n  ") +++
 foldr1 (\x y -> x ++ "\n |" +++ y) constructors ++++
- "  deriving Show"
+ " " +++ derivingClause
  where
    constructors = [gId f +++ foldr (+++) "" (map (gId) xx) | (f,xx) <- nonLexicalRules (lexical cat) rules]
                   ++ if lexical cat then [lexicalConstructor cat +++ "String"] else []
--- a/src/compiler/GF/Infra/Option.hs
+++ b/src/compiler/GF/Infra/Option.hs
@@ -132,7 +132,7 @@ data CFGTransform = CFGNoLR
  deriving (Show,Eq,Ord)

 data HaskellOption = HaskellNoPrefix | HaskellGADT | HaskellLexical
-                   | HaskellConcrete | HaskellVariants
+                   | HaskellConcrete | HaskellVariants | HaskellData
  deriving (Show,Eq,Ord)

 data Warning = WarnMissingLincat
@@ -531,7 +531,8 @@ haskellOptionNames =
     ("gadt",     HaskellGADT),
     ("lexical",  HaskellLexical),
     ("concrete", HaskellConcrete),
-     ("variants", HaskellVariants)]
+     ("variants", HaskellVariants),
+     ("data",     HaskellData)]

 -- | This is for bacward compatibility. Since GHC 6.12 we
 -- started using the native Unicode support in GHC but it
--- a/src/runtime/c/pgf/expr.c
+++ b/src/runtime/c/pgf/expr.c
@@ -1635,19 +1635,6 @@ pgf_print_context(PgfHypos *hypos, PgfPrintContext* ctxt,
 	}
 }

-PGF_API void
-pgf_print_expr_tuple(size_t n_exprs, PgfExpr exprs[], PgfPrintContext* ctxt,
-                     GuOut* out, GuExn* err)
-{
-	gu_putc('<', out, err);
-	for (size_t i = 0; i < n_exprs; i++) {
-		if (i > 0)
-			gu_putc(',', out, err);
-		pgf_print_expr(exprs[i], ctxt, 0, out, err);
-	}
-	gu_putc('>', out, err);
-}
-
 PGF_API bool
 pgf_type_eq(PgfType* t1, PgfType* t2)
 {
@@ -1683,6 +1670,168 @@ pgf_type_eq(PgfType* t1, PgfType* t2)
 	return true;
 }

+PGF_API PgfLiteral
+pgf_clone_literal(PgfLiteral lit, GuPool* pool)
+{
+	PgfLiteral new_lit = gu_null_variant;
+
+	GuVariantInfo inf = gu_variant_open(lit);
+	switch (inf.tag) {
+	case PGF_LITERAL_STR: {
+		PgfLiteralStr* lit_str     = inf.data;
+		PgfLiteralStr* new_lit_str =
+			gu_new_flex_variant(PGF_LITERAL_STR,
+						        PgfLiteralStr,
+						        val, strlen(lit_str->val)+1,
+						        &new_lit, pool);
+		strcpy(new_lit_str->val, lit_str->val);
+		break;
+	}
+	case PGF_LITERAL_INT: {
+		PgfLiteralInt *lit_int     = inf.data;
+		PgfLiteralInt *new_lit_int =
+			gu_new_variant(PGF_LITERAL_INT,
+						   PgfLiteralInt,
+						   &new_lit, pool);
+		new_lit_int->val = lit_int->val;
+		break;
+	}
+	case PGF_LITERAL_FLT: {
+		PgfLiteralFlt *lit_flt     = inf.data;
+		PgfLiteralFlt *new_lit_flt =
+			gu_new_variant(PGF_LITERAL_FLT,
+						   PgfLiteralFlt,
+						   &new_lit, pool);
+		new_lit_flt->val = lit_flt->val;
+		break;
+	}
+	default:
+		gu_impossible();
+	}
+
+	return new_lit;
+}
+
+PGF_API PgfExpr
+pgf_clone_expr(PgfExpr expr, GuPool* pool)
+{
+	PgfExpr new_expr = gu_null_variant;
+
+	GuVariantInfo inf = gu_variant_open(expr);
+	switch (inf.tag) {
+	case PGF_EXPR_ABS: {
+		PgfExprAbs* abs     = inf.data;
+		PgfExprAbs* new_abs =
+			gu_new_variant(PGF_EXPR_ABS,
+						   PgfExprAbs,
+						   &new_expr, pool);
+
+		new_abs->bind_type = abs->bind_type;
+		new_abs->id = gu_string_copy(abs->id, pool);
+		new_abs->body = pgf_clone_expr(abs->body,pool);
+		break;
+	}
+	case PGF_EXPR_APP: {
+		PgfExprApp* app     = inf.data;
+		PgfExprApp* new_app =
+			gu_new_variant(PGF_EXPR_APP,
+						   PgfExprApp,
+						   &new_expr, pool);
+		new_app->fun = pgf_clone_expr(app->fun, pool);
+		new_app->arg = pgf_clone_expr(app->arg, pool);
+		break;
+	}
+	case PGF_EXPR_LIT: {
+		PgfExprLit* lit     = inf.data;
+		PgfExprLit* new_lit =
+			gu_new_variant(PGF_EXPR_LIT,
+						   PgfExprLit,
+						   &new_expr, pool);
+		new_lit->lit = pgf_clone_literal(lit->lit, pool);
+		break;
+	}
+	case PGF_EXPR_META: {
+		PgfExprMeta* meta     = inf.data;
+		PgfExprMeta* new_meta =
+			gu_new_variant(PGF_EXPR_META,
+						   PgfExprMeta,
+						   &new_expr, pool);
+		new_meta->id = meta->id;
+		break;
+	}
+	case PGF_EXPR_FUN: {
+		PgfExprFun* fun     = inf.data;
+		PgfExprFun* new_fun =
+			gu_new_flex_variant(PGF_EXPR_FUN,
+						        PgfExprFun,
+						        fun, strlen(fun->fun)+1,
+						        &new_expr, pool);
+		strcpy(new_fun->fun, fun->fun);
+		break;
+	}
+	case PGF_EXPR_VAR: {
+		PgfExprVar* var     = inf.data;
+		PgfExprVar* new_var =
+			gu_new_variant(PGF_EXPR_VAR,
+						   PgfExprVar,
+						   &new_expr, pool);
+		new_var->var = var->var;
+		break;
+	}
+	case PGF_EXPR_TYPED: {
+		PgfExprTyped* typed = inf.data;
+
+		PgfExprTyped *new_typed =
+			gu_new_variant(PGF_EXPR_TYPED,
+						   PgfExprTyped,
+						   &new_expr, pool);
+		new_typed->expr = pgf_clone_expr(typed->expr, pool);
+		new_typed->type = pgf_clone_type(typed->type, pool);
+		break;
+	}
+	case PGF_EXPR_IMPL_ARG: {
+		PgfExprImplArg* impl     = inf.data;
+		PgfExprImplArg *new_impl =
+			gu_new_variant(PGF_EXPR_IMPL_ARG,
+						   PgfExprImplArg,
+						   &new_expr, pool);
+		new_impl->expr = pgf_clone_expr(impl->expr, pool);
+		break;
+	}
+	default:
+		gu_impossible();
+	}
+
+	return new_expr;
+}
+
+PGF_API PgfType*
+pgf_clone_type(PgfType* type, GuPool* pool)
+{
+	PgfType* new_type =
+		gu_new_flex(pool, PgfType, exprs, type->n_exprs);
+
+	size_t n_hypos = gu_seq_length(type->hypos);
+	new_type->hypos = gu_new_seq(PgfHypo, n_hypos, pool);
+	for (size_t i = 0; i < n_hypos; i++) {
+		PgfHypo* hypo     = gu_seq_index(type->hypos,     PgfHypo, i);
+		PgfHypo* new_hypo = gu_seq_index(new_type->hypos, PgfHypo, i);
+
+		new_hypo->bind_type = hypo->bind_type;
+		new_hypo->cid = gu_string_copy(hypo->cid, pool);
+		new_hypo->type = pgf_clone_type(hypo->type, pool);
+	}
+
+	new_type->cid = gu_string_copy(type->cid, pool);
+
+	new_type->n_exprs = type->n_exprs;
+	for (size_t i = 0; i < new_type->n_exprs; i++) {
+		new_type->exprs[i] = pgf_clone_expr(type->exprs[i], pool);
+	}
+
+	return new_type;
+}
+
 PGF_API prob_t
 pgf_compute_tree_probability(PgfPGF *gr, PgfExpr expr)
 {
--- a/src/runtime/c/pgf/expr.h
+++ b/src/runtime/c/pgf/expr.h
@@ -229,9 +229,14 @@ PGF_API_DECL void
 pgf_print_context(PgfHypos *hypos, PgfPrintContext* ctxt,
                  GuOut *out, GuExn *err);

-PGF_API_DECL void
-pgf_print_expr_tuple(size_t n_exprs, PgfExpr exprs[], PgfPrintContext* ctxt,
-                     GuOut* out, GuExn* err);
+PGF_API PgfLiteral
+pgf_clone_literal(PgfLiteral lit, GuPool* pool);
+
+PGF_API PgfExpr
+pgf_clone_expr(PgfExpr expr, GuPool* pool);
+
+PGF_API PgfType*
+pgf_clone_type(PgfType* type, GuPool* pool);

 PGF_API_DECL prob_t
 pgf_compute_tree_probability(PgfPGF *gr, PgfExpr expr);
--- a/src/runtime/haskell-bind/PGF2.hsc
+++ b/src/runtime/haskell-bind/PGF2.hsc
@@ -433,6 +433,7 @@ graphvizParseTree c opts e =
         c_opts <- newGraphvizOptions tmpPl opts
         pgf_graphviz_parse_tree (concr c) (expr e) c_opts out exn
         touchExpr e
+         touchConcr c
         s <- gu_string_buf_freeze sb tmpPl
         peekUtf8CString s

@@ -858,16 +859,7 @@ mkCallbacksMap concr callbacks pool = do
        Just (e,prob,offset') -> do poke poffset (fromIntegral offset')

                                    -- here we copy the expression to out_pool
-                                    c_e <- withGuPool $ \tmpPl -> do
-                                             exn <- gu_new_exn tmpPl
-        
-                                             (sb,out) <- newOut tmpPl
-                                             let printCtxt = nullPtr
-                                             pgf_print_expr (expr e) printCtxt 1 out exn
-                                             c_str <- gu_string_buf_freeze sb tmpPl
-
-                                             guin <- gu_string_in c_str tmpPl
-                                             pgf_read_expr guin out_pool tmpPl exn
+                                    c_e <- pgf_clone_expr (expr e) out_pool

                                    ep <- gu_malloc out_pool (#size PgfExprProb)
                                    (#poke PgfExprProb, expr) ep c_e
--- a/src/runtime/haskell-bind/PGF2/FFI.hsc
+++ b/src/runtime/haskell-bind/PGF2/FFI.hsc
@@ -513,9 +513,6 @@ foreign import ccall "pgf/expr.h pgf_compute"
 foreign import ccall "pgf/expr.h pgf_print_expr"
  pgf_print_expr :: PgfExpr -> Ptr PgfPrintContext -> CInt -> Ptr GuOut -> Ptr GuExn -> IO ()

-foreign import ccall "pgf/expr.h pgf_print_expr_tuple"
-  pgf_print_expr_tuple :: CSizeT -> Ptr PgfExpr -> Ptr PgfPrintContext -> Ptr GuOut -> Ptr GuExn -> IO ()
-
 foreign import ccall "pgf/expr.h pgf_print_type"
  pgf_print_type :: PgfType -> Ptr PgfPrintContext -> CInt -> Ptr GuOut -> Ptr GuExn -> IO ()

@@ -551,3 +548,6 @@ foreign import ccall "pgf/data.h pgf_lzr_index"

 foreign import ccall "pgf/data.h pgf_production_is_lexical"
  pgf_production_is_lexical :: Ptr PgfProductionApply -> Ptr GuBuf -> Ptr GuPool -> IO (#type bool)
+
+foreign import ccall "pgf/expr.h pgf_clone_expr"
+  pgf_clone_expr :: PgfExpr -> Ptr GuPool -> IO PgfExpr
--- a/src/runtime/java/jpgf.c
+++ b/src/runtime/java/jpgf.c
@@ -486,39 +486,8 @@ jpgf_literal_callback_match(PgfLiteralCallback* self, PgfConcr* concr,

 	PgfExprProb* ep = gu_new(PgfExprProb, out_pool);
 	ep->expr = gu_variant_from_ptr(get_ref(env, jexpr));
+	ep->expr = pgf_clone_expr(ep->expr, out_pool);
 	ep->prob = prob;
-
-	
-	{
-		// This is an uggly hack. We first show the expression ep->expr
-		// and then we read it back but in out_pool. The whole purpose
-		// of this is to copy the expression from the temporary pool
-		// that was created in the Java binding to the parser pool.
-		// There should be a real copying function or even better
-		// there must be a way to avoid copying at all.
-
-		GuPool* tmp_pool = gu_local_pool();
-
-		GuExn* err = gu_exn(tmp_pool);
-		GuStringBuf* sbuf = gu_new_string_buf(tmp_pool);
-		GuOut* out = gu_string_buf_out(sbuf);
-
-		pgf_print_expr(ep->expr, NULL, 0, out, err);
-
-		GuString str = gu_string_buf_data(sbuf);
-		size_t   len = gu_string_buf_length(sbuf);
-		GuIn* in = gu_data_in((uint8_t*) str, len, tmp_pool);
-
-		ep->expr = pgf_read_expr(in, out_pool, tmp_pool, err);
-		if (!gu_ok(err) || gu_variant_is_null(ep->expr)) {
-			throw_string_exception(env, "org/grammaticalframework/pgf/PGFError", "The expression cannot be parsed");
-			gu_pool_free(tmp_pool);
-			return NULL;
-		}
-
-		gu_pool_free(tmp_pool);
-	}
-
 	return ep;
 }

--- a/src/runtime/python/pypgf.c
+++ b/src/runtime/python/pypgf.c
@@ -1412,7 +1412,7 @@ pypgf_literal_callback_match(PgfLiteralCallback* self, PgfConcr* concr,

 	ExprObject* pyexpr;
 #if PY_MAJOR_VERSION >= 3
-	size_t chars;
+	int chars;
 	if (!PyArg_ParseTuple(result, "Ofi", &pyexpr, &ep->prob, &chars))
 	    return NULL;
 	*poffset = unicode_to_utf8_offset(sentence, chars);
@@ -1421,37 +1421,7 @@ pypgf_literal_callback_match(PgfLiteralCallback* self, PgfConcr* concr,
 	    return NULL;
 #endif

-	ep->expr = pyexpr->expr;
-
-	{
-		// This is an uggly hack. We first show the expression ep->expr
-		// and then we read it back but in out_pool. The whole purpose
-		// of this is to copy the expression from the temporary pool
-		// that was created in the Java binding to the parser pool.
-		// There should be a real copying function or even better
-		// there must be a way to avoid copying at all.
-
-		GuPool* tmp_pool = gu_local_pool();
-
-		GuExn* err = gu_exn(tmp_pool);
-		GuStringBuf* sbuf = gu_new_string_buf(tmp_pool);
-		GuOut* out = gu_string_buf_out(sbuf);
-
-		pgf_print_expr(ep->expr, NULL, 0, out, err);
-
-		GuIn* in = gu_data_in((uint8_t*) gu_string_buf_data(sbuf),
-		                      gu_string_buf_length(sbuf),
-		                      tmp_pool);
-
-		ep->expr = pgf_read_expr(in, out_pool, tmp_pool, err);
-		if (!gu_ok(err) || gu_variant_is_null(ep->expr)) {
-			PyErr_SetString(PGFError, "The expression cannot be parsed");
-			gu_pool_free(tmp_pool);
-			return NULL;
-		}
-
-		gu_pool_free(tmp_pool);
-	}
+	ep->expr = pgf_clone_expr(pyexpr->expr, out_pool);

 	Py_DECREF(result);