the GF syntax for identifiers is exteded with quoted forms, i.e. you could write for instance 'ab.c' and then everything between the quites is identifier. This includes Unicode characters and non-ASCII symbols. This is useful for automatically generated GF grammars.

src/runtime/c/pgf/expr.c

@@ -1,5 +1,6 @@
 #include "pgf.h"
 #include <gu/assert.h>
+#include <gu/utf8.h>
 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -166,6 +167,45 @@ pgf_expr_parser_getc(PgfExprParser* parser)
 	}
 }
 
+static bool
+pgf_is_ident_first(GuUCS ucs)
+{
+	return (ucs == '_') ||
+           (ucs >= 'a' && ucs <= 'z') ||
+           (ucs >= 'A' && ucs <= 'Z') ||
+           (ucs >= 192 && ucs <= 255 && ucs != 247 && ucs != 215);
+}
+
+static bool
+pgf_is_ident_rest(GuUCS ucs)
+{
+	return (ucs == '_') ||
+           (ucs == '\'') ||
+           (ucs >= '0' && ucs <= '9') ||
+           (ucs >= 'a' && ucs <= 'z') ||
+           (ucs >= 'A' && ucs <= 'Z') ||
+           (ucs >= 192 && ucs <= 255 && ucs != 247 && ucs != 215);
+}
+
+static bool
+pgf_is_normal_ident(PgfCId id)
+{
+	const uint8_t* p = (const uint8_t*) id;
+	GuUCS ucs = gu_utf8_decode(&p);
+	if (!pgf_is_ident_first(ucs))
+		return false;
+
+	for (;;) {
+		ucs = gu_utf8_decode(&p);
+		if (ucs == 0)
+			break;
+		if (!pgf_is_ident_rest(ucs))
+			return false;
+	}
+
+	return true;
+}
+
 static void
 pgf_expr_parser_token(PgfExprParser* parser)
 {
@@ -227,20 +267,32 @@ pgf_expr_parser_token(PgfExprParser* parser)
 		pgf_expr_parser_getc(parser);
 		parser->token_tag = PGF_TOKEN_COLON;
 		break;
-	case '_':
+	case '\'':
 		pgf_expr_parser_getc(parser);
-		parser->token_tag = PGF_TOKEN_WILD;
+
+		GuBuf* chars = gu_new_buf(char, parser->tmp_pool);
+		while (parser->ch != '\'' && parser->ch != EOF) {
+			if (parser->ch == '\\') {
+				pgf_expr_parser_getc(parser);
+			}
+			gu_buf_push(chars, char, parser->ch);
+			pgf_expr_parser_getc(parser);
+		}
+		if (parser->ch == '\'') {
+			pgf_expr_parser_getc(parser);
+			gu_buf_push(chars, char, 0);
+			parser->token_tag   = PGF_TOKEN_IDENT;
+			parser->token_value = chars;
+		}
 		break;
 	default: {
 		GuBuf* chars = gu_new_buf(char, parser->tmp_pool);
 
-		if (isalpha(parser->ch)) {
-			while (isalnum(parser->ch) || 
-			       parser->ch == '_' || 
-			       parser->ch == '\'') {
+		if (pgf_is_ident_first(parser->ch)) {
+			do {
 				gu_buf_push(chars, char, parser->ch);
 				pgf_expr_parser_getc(parser);
-			}
+			} while (pgf_is_ident_rest(parser->ch));
 			gu_buf_push(chars, char, 0);
 			parser->token_tag   = PGF_TOKEN_IDENT;
 			parser->token_value = chars;
@@ -268,7 +320,7 @@ pgf_expr_parser_token(PgfExprParser* parser)
 			}
 		} else if (parser->ch == '"') {
 			pgf_expr_parser_getc(parser);
-			
+
 			while (parser->ch != '"' && parser->ch != EOF) {
 				gu_buf_push(chars, char, parser->ch);
 				pgf_expr_parser_getc(parser);
@@ -924,6 +976,30 @@ pgf_expr_hash(GuHash h, PgfExpr e)
 	return h;
 }
 
+void
+pgf_print_cid(PgfCId id,
+			  GuOut* out, GuExn* err)
+{
+	if (pgf_is_normal_ident(id))
+		gu_string_write(id, out, err);
+	else {
+		gu_putc('\'', out, err);
+		const uint8_t* p = (const uint8_t*) id;
+		for (;;) {
+			GuUCS ucs = gu_utf8_decode(&p);
+			if (ucs == 0)
+				break;
+			if (ucs == '\'')
+				gu_puts("\\\'", out, err);
+			else if (ucs == '\\')
+				gu_puts("\\\\", out, err);
+			else
+				gu_out_utf8(ucs, out, err);
+		}
+		gu_putc('\'', out, err);
+	}
+}
+
 void
 pgf_print_literal(PgfLiteral lit,
 			      GuOut* out, GuExn* err)
@@ -973,7 +1049,7 @@ pgf_print_expr(PgfExpr expr, PgfPrintContext* ctxt, int prec,
 			if (abs->bind_type == PGF_BIND_TYPE_IMPLICIT) {
 				gu_putc('{', out, err);
 			}
-			gu_string_write(abs->id, out, err);
+			pgf_print_cid(abs->id, out, err);
 			if (abs->bind_type == PGF_BIND_TYPE_IMPLICIT) {
 				gu_putc('}', out, err);
 			}
@@ -1028,7 +1104,7 @@ pgf_print_expr(PgfExpr expr, PgfPrintContext* ctxt, int prec,
 		break;
 	case PGF_EXPR_FUN: {
 		PgfExprFun* fun = ei.data;
-		gu_string_write(fun->fun, out, err);
+		pgf_print_cid(fun->fun, out, err);
 		break;
 	}
 	case PGF_EXPR_VAR: {
@@ -1043,7 +1119,7 @@ pgf_print_expr(PgfExpr expr, PgfPrintContext* ctxt, int prec,
 		if (c == NULL) {
 			gu_printf(out, err, "#%d", evar->var);
 		} else {
-			gu_string_write(c->name, out, err);
+			pgf_print_cid(c->name, out, err);
 		}
 		break;
 	}
@@ -1074,7 +1150,7 @@ pgf_print_hypo(PgfHypo *hypo, PgfPrintContext* ctxt, int prec,
 {
     if (hypo->bind_type == PGF_BIND_TYPE_IMPLICIT) {
         gu_puts("({", out, err);
-        gu_string_write(hypo->cid, out, err);
+        pgf_print_cid(hypo->cid, out, err);
         gu_puts("} : ", out, err);
         pgf_print_type(hypo->type, ctxt, 0, out, err);
         gu_puts(")", out, err);
@@ -1083,7 +1159,7 @@ pgf_print_hypo(PgfHypo *hypo, PgfPrintContext* ctxt, int prec,
 
         if (strcmp(hypo->cid, "_") != 0) {
             gu_puts("(", out, err);
-            gu_string_write(hypo->cid, out, err);
+            pgf_print_cid(hypo->cid, out, err);
             gu_puts(" : ", out, err);
             pgf_print_type(hypo->type, ctxt, 0, out, err);
             gu_puts(")", out, err);
@@ -1117,7 +1193,7 @@ pgf_print_type(PgfType *type, PgfPrintContext* ctxt, int prec,
 			gu_puts(" -> ", out, err);
 		}
 
-		gu_string_write(type->cid, out, err);
+		pgf_print_cid(type->cid, out, err);
     
 		for (size_t i = 0; i < type->n_exprs; i++) {
 			gu_puts(" ", out, err);
@@ -1143,7 +1219,7 @@ pgf_print_type(PgfType *type, PgfPrintContext* ctxt, int prec,
 		
 		if (prec > 3) gu_putc(')', out, err);
 	} else {
-		gu_string_write(type->cid, out, err);
+		pgf_print_cid(type->cid, out, err);
 	}
 }