Initial commit

example/calc/calc.py

@@ -0,0 +1,96 @@
+# -----------------------------------------------------------------------------
+# calc.py
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0, "../..")
+
+from sly import Lexer, Parser
+
+class CalcLexer(Lexer):
+    tokens = (
+        'NAME', 'NUMBER',
+        )
+    ignore = ' \t'
+    literals = ['=', '+', '-', '*', '/', '(', ')']
+
+    # Tokens
+    NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
+
+    @_(r'\d+')
+    def NUMBER(self, t):
+        t.value = int(t.value)
+        return t
+
+    @_(r'\n+')
+    def newline(self, t):
+        self.lineno += t.value.count('\n')
+
+    def error(self, value):
+        print("Illegal character '%s'" % value[0])
+        self.index += 1
+
+class CalcParser(Parser):
+    tokens = CalcLexer.tokens
+    
+    precedence = (
+        ('left', '+', '-'),
+        ('left', '*', '/'),
+        ('right', 'UMINUS'),
+    )
+
+    def __init__(self):
+        self.names = { }
+
+    @_('statement : NAME "=" expression')
+    def statement_assign(self, p):
+        self.names[p[1]] = p[3]
+
+    @_('statement : expression')
+    def statement_expr(self, p):
+        print(p[1])
+
+    @_('''expression : expression '+' expression
+                     | expression '-' expression
+                     | expression '*' expression
+                     | expression '/' expression''')
+    def expression_binop(self, p):
+        if p[2] == '+':
+            p[0] = p[1] + p[3]
+        elif p[2] == '-':
+            p[0] = p[1] - p[3]
+        elif p[2] == '*':
+            p[0] = p[1] * p[3]
+        elif p[2] == '/':
+            p[0] = p[1] / p[3]
+
+    @_('expression : "-" expression %prec UMINUS')
+    def expression_uminus(self, p):
+        p[0] = -p[2]
+
+    @_('expression : "(" expression ")"')
+    def expression_group(self, p):
+        p[0] = p[2]
+
+    @_('expression : NUMBER')
+    def expression_number(self, p):
+        p[0] = p[1]
+
+    @_('expression : NAME')
+    def expression_name(self, p):
+        try:
+            p[0] = self.names[p[1]]
+        except LookupError:
+            print("Undefined name '%s'" % p[1])
+            p[0] = 0
+
+
+if __name__ == '__main__':
+    parser = CalcParser()
+    while True:
+        try:
+            s = input('calc > ')
+        except EOFError:
+            break
+        if s:
+            parser.parse(CalcLexer(s))