More doc updates

example/calc_prec/calc.py

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+# -----------------------------------------------------------------------------
+# 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 = { }
+
+    @_('NAME "=" expr')
+    def statement(self, p):
+        self.names[p.NAME] = p.expr
+
+    @_('expr')
+    def statement(self, p):
+        print(p.expr)
+
+    @_('expr "+" expr')
+    def expr(self, p):
+        return p.expr0 + p.expr1
+
+    @_('expr "-" expr')
+    def expr(self, p):
+        return p.expr0 - p.expr1
+
+    @_('expr "*" expr')
+    def expr(self, p):
+        return p.expr0 * p.expr1
+
+    @_('expr "/" expr')
+    def expr(self, p):
+        return p.expr0 / p.expr1
+
+    @_('"-" expr %prec UMINUS')
+    def expr(self, p):
+        return -p.expr
+
+    @_('"(" expr ")"')
+    def expr(self, p):
+        return p.expr
+
+    @_('NUMBER')
+    def expr(self, p):
+        return p.NUMBER
+
+    @_('NAME')
+    def expr(self, p):
+        try:
+            return self.names[p.NAME]
+        except LookupError:
+            print("Undefined name '%s'" % p.NAME)
+            return 0
+
+if __name__ == '__main__':
+    lexer = CalcLexer()
+    parser = CalcParser()
+    while True:
+        try:
+            text = input('calc > ')
+        except EOFError:
+            break
+        if text:
+            parser.parse(lexer.tokenize(text))