On Mon, 12 Jul 2010 16:22:28 -0400, bearophile <bearophileh...@lycos.com>
wrote:
Steven Schveighoffer:
bearophile:
> String mixins are a hack, just a bit better than C preprocessor
(because
> they are scoped), they are not a replacement of clean macros.
Interesting statement, can you back it up? :) What can you do with a
macro that you can't do with a mixin?
In the meantime others have already given you some answers, I can add
one example. The Brainfuck language allows you to do every kind of
thing, I have seen even compilers written in it, but its usage is very
unhandy, it's bug-prone, requires lot of code to do even simple things,
and it's very hard to modify and debug programs written in it. What I
meant is that string mixins in theory allow you to do many things, but
in practice you can't use them for complex tasks, and you can't modify
and fix the resulting code if you try to use them for more complex
tasks. They are not a long-term solution for a language that seriously
wants to improve over C and its preprocessor macros, they are a hack.
Brainfuck is basically a toy example of a language. Nobody uses it for
serious work. Mixins are much better than a hack, the syntax of using
them is just not polished. They are easy to use/understand because a)
people understand the language and b) people understand string
manipulation.
In my opinion the std.bitmanip.bitfields souce code is already past the
decency limit for string mixins, and I hope they will be replaced by
something better.
How would AST macros make std.bitmanip.bitfields easier to understand? I
have never seen it before, and I understood it after a couple minutes
reading. I bet the AST version would be actually harder to understand.
Most of the "ugliness" is the part that builds the accessors because it
contains so much concatenation, but that is what I was proposing. Having
used php for the last year in my job, there is one thing I appreciate:
with a language that is focused on string manipulation, it is so much
better to be able to simply output variables inside strings rather than
having to exit a quotation, and use a concatenation operator. With the
unused keyword macro, we can make string mixins much easier to
write/understand without the need to add AST macros.
I'll give you another example -- javascript and HTML editing. Most people
would prefer to just use the innerHTML component of an element than have
to use the DOM methods to create individual elements and add them as
children, etc.
I don't agree with Andrei when he says that CLisp macros (and even more
Scheme macros that are hygienic too) are as hairy and unmantenable as
code that uses string mixins heavily.
I don't have much experience with these languages except that in college
while taking a scheme course, I wanted to create a bonfire out of all
parentheses keys.
-Steve
