[erlang-questions] Changing the shell and module syntax and semantics

Thomas Lindgren <>
Thu Mar 8 12:50:06 CET 2007


--- Joe Armstrong <> wrote:

> all we need to do is add an invisible
> "-module(shell)" to
> the session, remember all the stuff that's typed in
> and
> as new functions come either compile the complete
> module (so far)
> or interpret the code.

I think Prolog can show the way in that case. In
Prolog, you can "consult" files to read in predicate
definitions, but also consult from a special name,
'user', where you type in definitions directly. Here
is an example: I consult from user, type in f/1, exit
the consult, then run f(X) (search for solutions
binding X). For those not familiar with Prolog, note
the uncanny similarity in syntax :-)

===========================================
localhost % gprolog 
GNU Prolog 1.3.0
By Daniel Diaz
Copyright (C) 1999-2007 Daniel Diaz
| ?- [user].
compiling user for byte code...
f(a).
f(b).

user compiled, 3 lines read - 262 bytes written, 6665
ms

yes
| ?- f(X).

X = a ? ;

X = b

yes
| ?- 

============================

(Reading from 'user' was terminated by EOF, control-D,
which doesn't show in the above.)

Happily, Richard O'Keefe probably knows all there is
to know about this topic already.

I would suggest a shell command for doing the above,
but rather than having an implicit module 'shell', I
would generalize it a bit. The command might be named
e.g., "def(my_module)" and could work like this:

- read forms until EOF
- stick "-module(my_module). -compile(export_all)." in
front of the forms
- compile and load them as my_module

It might be nice to be able to extend or revise an
existing module too, at least one created with def/1,
particularly if there is a compilation error ...
Anyway, such a capability would subsume your proposal.

Best,
Thomas




 
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