From af80858e888c5f36979da88fcb1080de7b848967 Mon Sep 17 00:00:00 2001
From: David Beazley <dave@dabeaz.com>
Date: Thu, 27 Oct 2022 13:44:12 -0500
Subject: Reorganization. Added makefile

---
 tests/yacc_simple.py | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 tests/yacc_simple.py

(limited to 'tests/yacc_simple.py')

diff --git a/tests/yacc_simple.py b/tests/yacc_simple.py
new file mode 100644
index 0000000..5261838
--- /dev/null
+++ b/tests/yacc_simple.py
@@ -0,0 +1,65 @@
+# -----------------------------------------------------------------------------
+# yacc_simple.py
+#
+# A simple, properly specifier grammar
+# -----------------------------------------------------------------------------
+import ply.yacc as yacc
+
+from calclex import tokens
+
+# Parsing rules
+precedence = (
+    ('left','PLUS','MINUS'),
+    ('left','TIMES','DIVIDE'),
+    ('right','UMINUS'),
+    )
+
+# dictionary of names
+names = { }
+
+def p_statement_assign(t):
+    'statement : NAME EQUALS expression'
+    names[t[1]] = t[3]
+
+def p_statement_expr(t):
+    'statement : expression'
+    print(t[1])
+
+def p_expression_binop(t):
+    '''expression : expression PLUS expression
+                  | expression MINUS expression
+                  | expression TIMES expression
+                  | expression DIVIDE expression'''
+    if t[2] == '+'  : t[0] = t[1] + t[3]
+    elif t[2] == '-': t[0] = t[1] - t[3]
+    elif t[2] == '*': t[0] = t[1] * t[3]
+    elif t[2] == '/': t[0] = t[1] / t[3]
+
+def p_expression_uminus(t):
+    'expression : MINUS expression %prec UMINUS'
+    t[0] = -t[2]
+
+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_name(t):
+    'expression : NAME'
+    try:
+        t[0] = names[t[1]]
+    except LookupError:
+        print("Undefined name '%s'" % t[1])
+        t[0] = 0
+
+def p_error(t):
+    print("Syntax error at '%s'" % t.value)
+
+yacc.yacc()
+
+
+
+
-- 
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