(j3.2006) Macro questions
Wed Jan 31 13:33:09 EST 2007
On Tuesday 30 January 2007 20:03, Malcolm Cohen wrote:
> The "easy fix" for the feature is to have $quote, e.g.
> ? INTEGER($quote KIND = kind) name
> where $quote protects the next token against expansion,
> i.e. it quotes it.
Actually quoting a token *after* substitution and concatenation is useful (for
example, in printing out messages), so it is better to have both $quote and
$unquote. And I would use parenthesis:
INTEGER($unquote("KIND") = kind) name
It would be useful if we can agree on using one of the unused special
characters for things macro (that don't make into real syntax). Aside from
$quote, examples include my "delimiters around macro actuals" [just use
"$(...)"], macro functions (like $unquote above).
Incidentally, FWEB uses $ for most macro syntax. So it is $IF, $DO, $QUOTE,
$EVAL, etc. I kind of like that, though MACRO IF etc. is OK as well. BTW, the
$EVAL is the equivalent of our macro assignment:
In FWEB one can do:
which saves keystrokes (at the expense of ugliness). $EVAL also does logical
expressions as well, which we don't do (we only do integers). If we had macro
functions, one could write $EVAL themselves:
MACRO FUNCTION EVAL(expression) RESULT(token)
MACRO INTEGER :: x
END MACRO FUNCTION
I plan to propose that MACRO FUNCTIONs be added to the language at the WG5
meeting. I find the macro feature very incomplete without them. I'll also
propose that LOGICAL local macro variables be supported (it seems very little
extra work and useful enough).
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