Thursday, October 23, 2014

Parser – Numbers (Operand State)

Upon making the next set of changes, I realized that State with Operator and Operand enumerators were not accurate terms for what the parser did with this option.  All Operator state did was prevent numeric constants, but still allowed other operand type tokens (like string constants, identifiers, and functions).  This was renamed Number with Yes and No enumerators, which more clearly expresses what the code does.

This change made it obvious where some simplifications could be made to the get token function of the translator.  The value of the number (previously state) argument was selecting number (Yes) if the desired data type was not the default data type value (indicating the caller wants an operator token).  When the desired data type is string, the number token would be invalid, so the condition of the desired data type is not string was added to the setting of the number argument.

Number tokens no longer are returned when looking for a string (an unknown token error will be returned).  For error tokens, there was a check for operator state and the data type was double (indicating a number error), or the desired data type is string, which set the token length to 1 (so the error only points to the first character) and the token data type set to None (to indicate to callers that there is no number error).  These situations now return an unknown token error for numbers with the length set to one and data type set to None, so this check was not needed.

The other check was much more involved (and confusing) but basically said if looking for an operand and there was not a number error, return an expression expected error.  Otherwise return a parser error.  This check was changed to if the desired data type was not empty (expecting operator) and not None (indicating a PRINT function is allowed) and there was an unknown token error, then return an expression expected error.

[branch parser commit 5690b1b4e9]

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