From: Andreas Schwarz <usenet@...>
Date: 2004-08-23T23:35:43+09:00
Subject: Re: How to check syntax

Graham Nicholls wrote:

> Andreas Schwarz wrote:
> 
> 
>>Graham Nicholls wrote:
>>
>>
>>>OK, so its not a syntax error. Pedants :-) There ought to be a utility to
>>>look for variable references, etc.
>>
>>This is almost impossible in dynamic languages like ruby. Variables can
>>be defined everywhere, in eval(), conditional code, etc. You don't find
>>out until you execute it.
> 
> I had a feeling that this was the case.
> 
>> > Now, I realize that this may be hard as
>>
>>>its presumably akin to part of writing a compile.  What I'd like to know,
>>>then is how to avoid the above - its a real nuisance in "scripting
>>>languages" (Oh and if you don't like that term, get over it - you know
>>>what I mean, python, perl(ugh!) Ruby & the like)
>>
>>Use unit tests.
> 
> Could you elucidate.  Typically this is pretty small stuff - my larger
> projects tend to be coded in C, although unit testing can presumably be
> applied there.
> 
> Heres a slice of code:
> 
> ,----[ /home/graham/src/hsb/add_logo ]
> | #!/usr/bin/env ruby
> | #
> | =begin
> | Parse an input file (which is intended to be an Informix -produced text
> | file containing PCL escape sequences) for a pattern which will introduce a
> | logo. The pattern looks like this:
[...]

> As you can see, theres not much to it - an hours work or so - I'd rather not
> have to spend much time writing testing - ISTM its easier to fix a bug when
> it rears than spend ages trying to eliminate all possible bugs

Your example seems to be very easy to test; feed it a few different 
files and compare the output to the expected result. This is especially 
helpful to make sure that you break anything when you change the code.