for in D versus C and C++

[Sean Kelly]

Walter Bright wrote:
> Georg Wrede wrote:
>> Sometimes I need to have a command line UI in a program. Such programs 
>> usually have 5 to 10 commands, with their parameters. One command per 
>> line.
>>
>> So far I have tested and split the command line with regular 
>> expressions, because using a parser generator has felt like shooting 
>> mosquitos with a shotgun.
>>
>> What would your strategy be?
> 
> If it's 5 or 10, you can get by with ad-hoc. But if you find yourself 
> repeatedly fixing bugs in the parsing, it's time to consider a more 
> principled approach.

I've found that once I created one lexer it could be re-used pretty 
easily for other languages too.  And recursive descent parsers are 
trivial to write.  It may be overkill for command-line parameters, but 
for anything remotely structured it's generally worth using.