From: Eric S. Raymond <esr@thyrsus,com>
Date: Wed, 14 Jan 2004 04:01:16 +0000 (+0000)
Subject: Added logical expressions.
X-Git-Tag: 1.0~205
X-Git-Url: http://thyrsus.com/gitweb/?a=commitdiff_plain;h=26d1be8b4e9fddf7a4034aeaac64c86eb8b6f88c;p=mad.git

Added logical expressions.
---

diff --git a/mad b/mad
index d892624..f32c76c 100755
--- a/mad
+++ b/mad
@@ -1,19 +1,19 @@
 #!/usr/bin/env python
-# -----------------------------------------------------------------------------
-# calc.py
-#
-# A simple calculator with variables.   This is from O'Reilly's
-# "Lex and Yacc", p. 63.
-# -----------------------------------------------------------------------------
 
 tokens = (
-    'NAME','NUMBER',
-    'PLUS','MINUS','TIMES','DIVIDE','EQUALS',
+    'NAME','INTEGER', 'FLOAT',
     'LPAREN','RPAREN',
+    'PLUS','MINUS','TIMES','DIVIDE','EQUALS',
+    'NOT', 'OR', 'AND', 'THEN', 'EQV',
     )
 
 # Tokens
 
+t_NOT      = r'\.NOT\.'
+t_OR      = r'\.OR\.'
+t_AND     = r'\.AND\.'
+t_THEN    = r'\.OR\.'
+t_EQV     = r'\.EQV\.'
 t_PLUS    = r'\+'
 t_MINUS   = r'-'
 t_TIMES   = r'\*'
@@ -22,17 +22,10 @@ t_EQUALS  = r'='
 t_LPAREN  = r'\('
 t_RPAREN  = r'\)'
 t_NAME    = r'[a-zA-Z_][a-zA-Z0-9_]*'
+t_FLOAT   = r'\d+\.\d*'
+t_INTEGER = r'\d+'
 
-def t_NUMBER(t):
-    r'\d+'
-    try:
-        t.value = int(t.value)
-    except ValueError:
-        print "Integer value too large", t.value
-        t.value = 0
-    return t
-
-t_ignore = " \t"
+t_ignore = " "
 
 def t_newline(t):
     r'\n+'
@@ -49,6 +42,11 @@ lex.lex()
 # Parsing rules
 
 precedence = (
+    ('left','EQV'),
+    ('left','THEN'),
+    ('left','OR'),
+    ('left','AND'),
+    ('right','NOT'),
     ('left','PLUS','MINUS'),
     ('left','TIMES','DIVIDE'),
     ('right','UMINUS'),
@@ -57,18 +55,30 @@ precedence = (
 def p_statement_assign(t):
     'statement : NAME EQUALS expression'
     t[0] = ('substitution', t[1], t[3])
+    print t[0]
 
 def p_statement_expr(t):
     'statement : expression'
     t[0] = t[1]
     print t[0]
 
-def p_expression_binop(t):
+def p_expression_binop1(t):
     '''expression : expression PLUS expression
                   | expression MINUS expression
                   | expression TIMES expression
                   | expression DIVIDE expression'''
-    t[0] = (t[2], t[1], t[3])
+    t[0] = (t[2].lower(), t[1], t[3])
+
+def p_expression_binop2(t):
+    '''expression : expression OR expression
+                  | expression AND expression
+                  | expression THEN expression
+                  | expression EQV expression'''
+    t[0] = (t[2][1:-1].lower(), t[1], t[3])
+
+def p_expression_not(t):
+    'expression : NOT expression %prec NOT'
+    t[0] = ('not', t[2])
 
 def p_expression_uminus(t):
     'expression : MINUS expression %prec UMINUS'
@@ -78,13 +88,17 @@ def p_expression_group(t):
     'expression : LPAREN expression RPAREN'
     t[0] = t[2]
 
-def p_expression_number(t):
-    'expression : NUMBER'
-    t[0] = t[1]
+def p_expression_integer(t):
+    'expression : INTEGER'
+    t[0] = ('integer', t[1])
+
+def p_expression_float(t):
+    'expression : FLOAT'
+    t[0] = ('float', t[1])
 
 def p_expression_name(t):
     'expression : NAME'
-    t[0] = t[1]
+    t[0] = ('variable', t[1])
 
 def p_error(t):
     print "Syntax error at '%s'" % t.value