Re: macros, was Looking for volunteers for XL

On 2011-12-13, Kaz Kylheku <kaz@kylheku.com> wrote:
> Real macros let you do that: make robust languages that make heavy, dense use
> of those macros, not only some syntactic sugar that is to be sprinkled very
> sparingly.
> [Seems to me that what you really want here is in-line functions. Macros are
> useful for other stuff, too. -John]


Inline functions don't always fit the bill.


For instance, try this exercise:


Implement the operator or2(A, B) which does this:


1. A is evaluated. If A is nonzero, then the value of A is returned.
2. Otherwise, B is evaluated and its value is returned.


You cannot write this as an inline function or as a non-kludgy macro in C.


Yet this or2 is not some esoteric macro either: it's a simple operator that
is only a tiny semantic modification to C's || and ?: operators.


Both arguments to the macro are expressions! It doesn't reinterpret their
syntax in any way; it just arranges for their evaluation.
[Yeah, you need inline functions with call by name and reference variables.
Yuck. -John]

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