dsimcha wrote:
== Quote from BCS (n...@anon.com)'s article
Show me ONE thing that can be done using run time meta programming that can't
be done as well or better with run time, non-dynamic, non-meta and/or compile
time meta. Unless I'm totally clueless as to what people are talking about
when they say runtime meta, I don't think you will be able to. Anything that
amounts to making the syntax look nicer can be done as compile time meta
and anything else can be done with data structure walking and interpretation.
All of that is available in non dynamic languages.
I guess I should concede the eval function but if you don't like CTFE+mixin...
Oh come on. I'm as much a fan of D metaprogramming as anyone, but even I admit
that there are certain things that static languages just suck at. One day I got
really addicted to std.algorithm and decided I wanted similar functionality for
text filters from a command line, so I wrote map, filter and count scripts that
take predicates specified at the command line.
filter.py:
import sys
pred = eval('lambda line: ' + sys.argv[2])
for line in open(sys.argv[1]):
if pred(line) :
print line.strip()
Usage:
filter.py foo.txt "float( line.split()[1]) < 5.0"
Metaprogramming isn't very rigorously defined, but this has to qualify. Try
writing something similar in D.
eval rocks.
Andrei
