On 2017-04-19 02:30, Walter Bright wrote:
I'm not saying you cannot do cool and useful things with AST macros. My
position is it encourages absolutely awful code as (usually
inexperienced) programmers compete to show how clever their macros are.
The language gets balkanized into a collection of dialects that are
unrecognizable across user groups.
As a compiler dev who gets stuck figuring out users' bug reports,
dealing with templates is bad enough (the first thing I do with a bug
report is redo it to remove all the templates). I do not want to deal
with some custom syntax. If I may pull the "I'm older" card, programmers
will find as they gain experience that the AST macros are just not worth
it.
This disastrous state of affairs has occurred with every language that
supports macros.
If you want a nauseous example, check out the Boost C preprocessor
metaprogramming library. Or C++ expression templates - so cool, and yet
so utterly wretched.
Reminds me of a story from the 1980s. Microsoft's MASM stood for "Macro
Assembler". Inevitably, Microsoft programmers invented a pile of macros
that sort of turned asm programming into a pseudo-high-level language.
This was shipped with every copy of MASM.
A friend of mine who worked at MS was once given the task of fixing a
bug in 50K of MASM code written in this macro language. The author of it
had long since moved on. Every coder assigned to this task failed. My
friend got it fixed in a couple hours. He was asked by his astonished
manager how he'd managed to do it:
"I assembled the code into an object file. Then I disassembled it with
Zortech's OBJ2ASM, figured out how to fix it, then submitted the
disassembled code as the new source code."
I have a suspension that it's the name "macro" that is the problem here.
It leaves a bad taste due to issues with macros in the past.
--
/Jacob Carlborg
