From 53f1b9251440b263d1605b86090e71cf09f6aad1 Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@fri.uni-lj.si>
Date: Sun, 15 May 2016 18:31:42 +0200
Subject: Hack in support for DCGs in Prolog parser

---
 prolog/lexer.py  |  1 +
 prolog/parser.py | 38 ++++++--------------------------------
 2 files changed, 7 insertions(+), 32 deletions(-)

diff --git a/prolog/lexer.py b/prolog/lexer.py
index f905a2b..f2b19dc 100644
--- a/prolog/lexer.py
+++ b/prolog/lexer.py
@@ -27,6 +27,7 @@ import ply.lex as lex
 # tokens; treat operators as names if followed by (
 operators = {
     r':-':  'FROM',
+    r'-->':  'FROMDCG',
     r'->':  'IMPLIES',
     r'\+':  'NOT',
     r'not': 'NOT',
diff --git a/prolog/parser.py b/prolog/parser.py
index 4a3f4b5..8fe96da 100644
--- a/prolog/parser.py
+++ b/prolog/parser.py
@@ -21,7 +21,7 @@ from .util import Token
 
 # PARSER
 precedence = (
-    ('nonassoc', 'FROM'),
+    ('nonassoc', 'FROM', 'FROMDCG'),
     ('right', 'IMPLIES'),
     ('right', 'NOT'),
     ('nonassoc', 'EQU', 'NEQU', 'EQ', 'NEQ', 'UNIV', 'IS', 'EQA', 'NEQA', 'LT', 'LE', 'GT', 'GE', 'LTL', 'LEL', 'GTL', 'GEL', 'IN', 'INS', 'THROUGH', 'EQFD', 'NEQFD', 'LTFD', 'LEFD', 'GTFD', 'GEFD'),
@@ -51,7 +51,8 @@ def p_clause_head(p):
     'clause : head PERIOD'
     p[0] = Tree('clause', [p[1], make_token(p, 2)])
 def p_clause_rule(p):
-    'clause : head FROM or PERIOD'
+    '''clause : head FROM or PERIOD
+              | head FROMDCG or PERIOD'''
     p[0] = Tree('clause', [p[1], make_token(p, 2), p[3], make_token(p, 4)])
 
 def p_head(p):
@@ -198,37 +199,10 @@ def p_clpr_more(p):
     '''clpr : clpr_constr COMMA clpr
             | clpr_constr SEMI clpr'''
     p[0] = Tree('clpr', [p[1], make_token(p, 2), p[3]])
-
+# XXX temporary until the new parser is in place, this also covers { } notation for DCGs
 def p_clpr_constr(p):
-    '''clpr_constr : clpr_expr LT clpr_expr
-                   | clpr_expr GT clpr_expr
-                   | clpr_expr LE clpr_expr
-                   | clpr_expr GE clpr_expr
-                   | clpr_expr NEQA clpr_expr
-                   | clpr_expr EQA clpr_expr
-                   | clpr_expr EQU clpr_expr'''
-    p[0] = Tree('clpr_constr', [p[1], make_token(p, 2), p[3]])
-
-def p_clpr_expr_value(p):
-    '''clpr_expr : VARIABLE
-                 | UINTEGER
-                 | UREAL'''
-    p[0] = Tree('clpr_expr', [make_token(p, 1)])
-def p_clpr_expr_unary(p):
-    '''clpr_expr : MINUS clpr_expr %prec UMINUS
-                 | PLUS clpr_expr %prec UPLUS'''
-    p[0] = Tree('clpr_expr', [make_token(p, 1), p[2]])
-def p_clpr_expr_binary(p):
-    '''clpr_expr : clpr_expr PLUS clpr_expr
-                 | clpr_expr MINUS clpr_expr
-                 | clpr_expr STAR clpr_expr
-                 | clpr_expr DIV clpr_expr
-                 | clpr_expr POW clpr_expr
-                 | clpr_expr NAME clpr_expr'''  # XXX a hack to allow (X)*(X) without spaces
-    p[0] = Tree('clpr_expr', [p[1], make_token(p, 2), p[3]])
-def p_clpr_expr_parens(p):
-    'clpr_expr : LPAREN clpr_expr RPAREN'
-    p[0] = Tree('clpr_expr', [make_token(p, 1), p[2], make_token(p, 3)])
+    'clpr_constr : term'
+    p[0] = p[1]
 
 def p_error(t):
     if t is None:
-- 
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