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- A slightly more powerful calculator that supports variables,
- plus some scientific functions like log(), sqr(), sin() etc.
- Most notably, this example demonstrates error handling.
- If/when one of your rule handlers comes across a condition
- which constitutes an error, but which the parser doesn't or can't
- pick up (eg division by zero), the handler should do:
- return self.error("string-describing-the-error")
- This will cause the parser to go into error handling mode.
- Also, your rules can pick up errors, by using the magic
- target name 'error'. Within error handling code, the
- 'lasterror' attribute of the parser object will be a
- 3-tuple:
- (line-num, msg, near-token)
- where:
- - 'line-num' is the input line at which the error (most likely)
- occured,
- - 'msg' is the error message text (supplied by either your own
- prior 'self.error(somestring)' call, or by the parser itself
- - 'near-token' is a string, the input token which triggered the
- error condition
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