The expected data type member of the Expression Info structure was initialized during table initialization based on the type (operator or function), number of operands and data types of the operands. This variable was moved to the table entry so that the preset expression info instances are not modified. This resolved the issue with the REPEAT$ function. An initialization value needed to be added to all of the table entries, a drawback of the current flat table entry array (though this will be changed in time). The default data type value was used.
This is about the end of the preliminary changes for the table. The next post will begin to describe the new table design. Since the changes will be significant, an attempt will be made to transition to the new design in a series of smaller changes. The movement of the expected data type could be considered the first of these changes.
[branch table commit 81992b2d51]
Sunday, December 7, 2014
Pre-Table – Expression Return Data Type
The data type table entry member was originally used for both the next expected token data type for a command and the return data type for operators and functions. The next expected data type was used with the now replaced token centric translator. Since the translator is now command centric, a next expected data type for commands is not needed. Since the return data type is expression related, it was moved into the Expression Info structure.
The preset expression info structure instances were updated to include a return data type. The table entries were updated where the data type initialization value was removed and the expression info structure pointer name updated or the return data type value added to the expression structure constructor call.
For the REPEAT$ function entry, the same preset expression info structure instance that is also used by several assign operators could not be used since the REPEAT$ function required a different expected data type.
The data type access function was replaced with a return data type function that checks if the expression info structure is present before attempting to access the return data type member. If the structure is not present, the None data type is returned.
[branch table commit 0186dcb76b]
The preset expression info structure instances were updated to include a return data type. The table entries were updated where the data type initialization value was removed and the expression info structure pointer name updated or the return data type value added to the expression structure constructor call.
For the REPEAT$ function entry, the same preset expression info structure instance that is also used by several assign operators could not be used since the REPEAT$ function required a different expected data type.
The data type access function was replaced with a return data type function that checks if the expression info structure is present before attempting to access the return data type member. If the structure is not present, the None data type is returned.
[branch table commit 0186dcb76b]
Pre-Table – Multiple Member
The multiple table entry member identified codes that either could be the first word of a two-word command (for example INPUT), was a two-word command (INPUT PROMPT), could be the first character of a two-character operator (<), or was a two-character operator (<=). Having an entire member for just this was unnecessary since a flag could be used for this purpose. In addition, it was not necessary to identify two-character operators.
Therefore, the multiple table entry member was replaced with a new Two table flag (a Multiple table flag already existed) and its access function removed. The Multiple enumeration contained separate enumerators for both characters and words, though were assigned to the same value and even contained enumerators for three characters or words, even though there were no codes that used these. This enumeration was removed.
Some changes were made to the Table Flag enumeration, including assigning it an underlying type of an unsigned integer (32 bits). Instead of assigning the enumerators to hard to read hexadecimal constants, they were assigned values using the shift operator where an unsigned one value is shifted by a unique number of bits. The shift operation is calculated during compilation. The Null table flag enumerator was removed; the default table flag value (TableFlag{}) is used instead. The flag table entry member type was also changed to an unsigned integer. The has flag access functions were changed to return a boolean value.
The parser get identifier and get operator routines were updated to use the has flag access function with the Two flag instead of using the multiple access function. In the table header file, there were a few remaining previously missed uses of a Qt type (quint16) on function pointer definitions that were replaced with the standard equivalent type (uint16_t).
[branch table commit 2f5edfc30e]
Therefore, the multiple table entry member was replaced with a new Two table flag (a Multiple table flag already existed) and its access function removed. The Multiple enumeration contained separate enumerators for both characters and words, though were assigned to the same value and even contained enumerators for three characters or words, even though there were no codes that used these. This enumeration was removed.
Some changes were made to the Table Flag enumeration, including assigning it an underlying type of an unsigned integer (32 bits). Instead of assigning the enumerators to hard to read hexadecimal constants, they were assigned values using the shift operator where an unsigned one value is shifted by a unique number of bits. The shift operation is calculated during compilation. The Null table flag enumerator was removed; the default table flag value (TableFlag{}) is used instead. The flag table entry member type was also changed to an unsigned integer. The has flag access functions were changed to return a boolean value.
The parser get identifier and get operator routines were updated to use the has flag access function with the Two flag instead of using the multiple access function. In the table header file, there were a few remaining previously missed uses of a Qt type (quint16) on function pointer definitions that were replaced with the standard equivalent type (uint16_t).
[branch table commit 2f5edfc30e]
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