From d913f0f62ba5756c0848f7e91374373fe768d74e Mon Sep 17 00:00:00 2001
From: Niles Rogoff <me@niles.xyz>
Date: Sat, 25 Mar 2017 14:28:44 -0400
Subject: [PATCH] Parser works in general, still has infinite loops if you
 specify recursive grammar in the wrong order

---
 parser.py | 109 +++++++++++++++++-------------------------------------
 1 file changed, 34 insertions(+), 75 deletions(-)

diff --git a/parser.py b/parser.py
index 958046d..d4ccf24 100644
--- a/parser.py
+++ b/parser.py
@@ -1,19 +1,6 @@
 import sys
 sys.path.append(".")
 import lexer
-grammar = {
-        "e": [
-            #[["nonterminal", "t"], ["terminal", ["mathbinop", "+"]], ["nonterminal", "e"]],
-            [["nonterminal", "t"]],
-        ],
-        "t": [
-            #[["terminal", ["integer"]], ["terminal", ["mathbinop", "*"]], ["nonterminal", "t"]],
-            [["terminal", ["integer"]]],
-            #[["terminal", ["parens", "("]], ["nonterminal", "e"], ["terminal", ["parens", ")"]]],
-        ],
-        "order": ["e", "t"]
-}
-
 def term(t_type, literal = False):
     global tokens_ptr, tokens
     this_token = tokens[tokens_ptr]
@@ -25,69 +12,41 @@ def term(t_type, literal = False):
         return True
     return literal == this_token.matched_string
 
-compiled = {}
-def build_test(): # I don't know how, I don't know why, and I don't know where, but this code has a race condition in it. It's late and I'll fix it later
-    for x, y in grammar.items():
-        if x == "order": continue
-        built_outer = []
-        for l in y:
-            # l is line 6, 7, 10, 11, 12
-            built = []
-            for sym in l:
-                if sym[0] == "terminal":
-                    built.append(lambda: term(*sym[1]))
-                else:
-                    built.append(lambda: compiled[sym[1]]())
-            def temp_inner(built):
-                for f in built:
-                    if not f():
-                        return False
-                return True
-            built_outer.append(lambda: temp_inner(built))
-        def temp():
-            global tokens_ptr
-            save = tokens_ptr
-            for f in built_outer:
-                tokens_ptr = save
-                if not f():
-                    return False
-            return True
-        compiled[x] = temp
+grammar = {
+        "e": [
+            [["nonterminal", "t"], ["terminal", ["mathbinop", "+"]], ["nonterminal", "e"]],
+            [["nonterminal", "t"]],
+        ],
+        "t": [
+            [["terminal", ["integer"]], ["terminal", ["mathbinop", "*"]], ["nonterminal", "t"]],
+            [["terminal", ["integer"]]],
+            [["terminal", ["parens", "("]], ["nonterminal", "e"], ["terminal", ["parens", ")"]]],
+        ],
+        "order": ["e", "t"]
+}
+
+def match_syms(syms):
+    # return term(a) and term(b) and term(c)
+    for sym in syms:
+        if not match_sym(sym):
+            return False
+    return True
+
+def match_sym(sym):
+    if sym[0] == "terminal":
+        return term(*(sym[1]))
+    return match_nterm(sym[1])
+
+def match_nterm(nterm):
+    global tokens_ptr
+    save = tokens_ptr
+    for f in grammar[nterm]:
+        tokens_ptr = save
+        if match_syms(f):
+            return True
+    return False
 
-tokens = lexer.lex("10")
-tokens_ptr = 0
-build_test()
-print(compiled["e"]())
-print(tokens_ptr)
-"""
 tokens = lexer.lex("(10+1)*3")
 tokens_ptr = 0
-def e1():
-    return t() and term("mathbinop","+") and e()
-def e2():
-    return t()
-def e():
-    global tokens_ptr
-    save = tokens_ptr
-    for f in [e1, e2]:
-        tokens_ptr = save
-        if f():
-            return True
-    return False
-def t1():
-    return term("integer") and term("mathbinop", "*") and t()
-def t2():
-    return term("integer")
-def t3():
-    return term("parens", "(") and e() and term("parens", ")")
-def t():
-    global tokens_ptr
-    save = tokens_ptr
-    for f in [t1, t2, t3]:
-        tokens_ptr = save
-        if f():
-            return True
-    return False
-print(e())
+print(match_nterm("e"))
 print(tokens_ptr)
-"""