Re: [Scheme-reports] REPL

[Alex Shinn <alexshinn@x>]

On Fri, Nov 16, 2012 at 4:18 PM, Helmut Eller <eller.helmut@x> wrote:

So how are we going to make (example life) available?  The only way I
know is to exit from Chibi Scheme, create a directory example/, move
life.scm to example/life.sld, restart Chibi with extra command line
options:

Chibi's module system is based on Scheme48.  It supports

pre-defined modules, modules inferred from file lookups, and

direct manipulation of the (meta) module (which in Scheme48

is called config).  There's a shortcut to do this from the extended

repl provided by (chibi repl):

> @meta (define-library (math) (export pi) (import (scheme base)) (begin (define pi 3.14)))

> (import (math))

> pi

3.14

OK, that was easy.  But how do we run the modified program?  Redefinition
of the 'life function, as you suggested, is not an option as the
life-print function is not even exported.

Again, Chibi provides many ways to do this.  Probably the

most appropriate here is the (chibi reload) module:

> (import (chibi reload))

> (reload-modified-modules)

From the (chibi repl) you could enter the (example life) module

and edit it interactively:

> @in (example life)

(example life)> (define life-print ...)

(example life)> @in

> 

Alternately you can use the module introspection from the

(chibi modules) library which is how (chibi repl) does its work.

These extensions are more powerful than simply mutating

imported bindings.  Moreover, they preserve abstraction.

It is possible in Chibi to use modules as a security mechanism,

to run untrusted code, controlling exactly which bindings

are available and not allowing the code to affect other parts

of the system.

-- 

Alex

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