While modifying the translator routines to throw exceptions, it was noticed that some minor improvements could be made. The first of these is with calls to the get token function. There was a similar pattern to most of the calls to this function, where the call was in a try block and for caught errors, the error was set to an appropriate error.
An error status argument was added to the get token function. The caller puts its desired error status to be returned when the parser returns an Unknown Token. With this change, the caller no longer needs to catch errors from the get token function call. Several of the callers need the parser error to be thrown as is, so if the error status argument is a null status, the parser error is thrown as is. The first status enumerator was assigned to a value of one so that a null status is not one of the existing enumerators.
[branch misc-cpp-stl commit 950d3cf9ed]
Thursday, November 27, 2014
Translator Exceptions – Expressions
The get expression function was modified to throw errors. The return type was removed since a no exception return now indicates success. The temporary error tokens for errors no longer need to be created. The Done status that was previously returned for success was no longer used, so this status enumerator was removed.
All callers of the get expression function were modified for an error being thrown, which for the most part meant catching errors instead of looking for an error return status. However, there was an issue with how errors were processed when an unexpected unary operator token appeared.
When an unexpected unary operator appeared, get expression returned an "expected binary operator or end-of-statement" error along with the unary operator token. When another error was appropriate, the caller essentially ignored this error when it a unary operator, and threw the appropriate error. Now that get expression throws an error, there is no token returned, so callers cannot look for a unary operator token. The callers were were modified to look for this error and then throw the appropriate error.
[branch misc-cpp-stl commit 697a0d25d8]
All callers of the get expression function were modified for an error being thrown, which for the most part meant catching errors instead of looking for an error return status. However, there was an issue with how errors were processed when an unexpected unary operator token appeared.
When an unexpected unary operator appeared, get expression returned an "expected binary operator or end-of-statement" error along with the unary operator token. When another error was appropriate, the caller essentially ignored this error when it a unary operator, and threw the appropriate error. Now that get expression throws an error, there is no token returned, so callers cannot look for a unary operator token. The callers were were modified to look for this error and then throw the appropriate error.
[branch misc-cpp-stl commit 697a0d25d8]
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