"Justin C. Sherrill" wrote:
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>Implementing a language-based shell happens to most every language;

First, a clarification -- I'm talking about a command shell (like tcsh
or bash), not an interactive interpreter like the standard python
interpreter or the read-eval-print loop (REPL) of lisp systems.  The
latter could, I suppose, be used as a command shell by using language
features (like the "os" module in python) to execute system commands.
But that would be incredibly tedious.

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>there's psh, the Perl shell, for instance:
>
>http://www.focusresearch.com/gregor/sw/psh/

This seems to be an ab initio effort to build a shell with perl-like
language features, not actually built on perl.

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>There's also perlsh or Shell.pm, which come with Perl. 

That seems to be a REPL.  Ie, it helps developing perl programs, but
is not a substitute for a command shell.

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>For other languages - lazy searching turns up these things:
>
>Interactive Ruby Shell:
>http://en.wikipedia.org/wiki/Interactive_Ruby_Shell

This too is a REPL.

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>tcl shell?
>http://fringe.davesource.com/Fringe/Computers/Languages/tcl_tk/tcl_shell.html

REPL, as far as I can tell.

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>php shell:
>http://jan.kneschke.de/projects/php-shell/

REPL.

All the REPLs above are comparable to the standard python interactive
interpreter.  ipython is something else.

Rahul