(j3.2006) Macro questions

[Aleksandar Donev]

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:

 MACRO kind=expression
 WRITE(*,*) 3_kind

In FWEB one can do:

     WRITE(*,*) 3_$EVAL(expression)

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
 MACRO x=token
 MACRO token=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).

Best,
Aleks