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Support for interactive interpreters...

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January 17, 2001 05:16
Support for interactive interpreters...
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I'm actually not following this list from close and I searching the archives
isn't that easy yet, so pardon me if this was already brought up.

I work with Perl and I also work with Tcl, and one thing I actually like
about Tcl is that it's interactive like a shell, i.e. it gives you a prompt,
where you type commands in and, if you type a whole command by the end of
the line, it executes it, otherwise, it gives you another prompt and keeps
reading more lines until the whole command is typed, when it's executed. I
think this is particularly useful for:
a) testing features (what the value of ... would be if I ...?)
b) debugging (what is the value of the variable ...?/what would the function
... return if I give it value ...?) and building custom debuggers
c) learning modules' interfaces
d) making changes at runtime (I will change the value of this variable

I understand the Perl 5's debugger can handle some of these tasks, but I
argue that its support is quite incomplete, it's hard to do if's or while
loops, and it's very hard (I would say impossible) to customize the debugger
for some of the uses above.

Tcl manages this by having a function that gets a line of command and
returns wheter it's complete, or another line should be read to try to
complete it. Of course Tcl can do it because it's much simpler than Perl in
its syntax, having this done in Perl is a much more complex subject.

Still, I think it's worth it. And now is for sure the time to think on this
kind of thing. After the implementation is done, if it's there, it's there,
otherwise, it will probably never be!

Thanks a lot.


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