source: project/wiki/eggref/5/live-define @ 37447

== live-define
[[toc:]]
Hack to simplify some cases of interactive development.


=== Requirements
* matchable


=== Documentation
<macro> (define name (lambda arguments body ...))</macro>
<macro> (define (name arguments) body ...)</macro>

A macro that replaces the standard Scheme {{define}} with one that, when it detects that a procedure is bound to {{name}}, mutates that procedure in place instead of binding the name to a new procedure.

This is useful in situations where you pass the procedure {{name}} as an argument to another and want to change it’s behavior while the program is running. For example by using your text editor’s facility to send code to a running instance of csi.

'''Please note that this is only intented to be used within the interpreter and will probably break in various ways if used in compiled code'''


=== Examples
This is a pretty contrived example, but it shows the modified behavior quite well.

Run it with {{csi -s example.scm}}

<enscript highlight="scheme">    
(import srfi-18)

;; try commenting this next line to see the standard behavior
(import live-define)

(define (thread-proc thunk)
  (lambda ()
    (let lp ()
      (thread-sleep! 1)
      (thunk)
      (lp))))

(define (the-thunk)
  (print "hi!"))

(thread-start! (thread-proc the-thunk))
;; -> prints "hi!" every second

(thread-sleep! 5)

(define (the-thunk)
  (print "coucou !"))
;; -> thread now prints "coucou !" every second

(thread-sleep! 5)
</enscript>


=== Version History

==== Version 1.1
30 November 2018

* Fix a bug that prevented the redefinition of a symbol imported from a module


==== Version 1.0
30 November 2018

* Original release


=== Source repository
Source available in [[https://www.upyum.com/cgit.cgi/live-define/|a git repository]]

Bug reports and patches welcome! Bugs can be reported to kooda@upyum.com


=== Authors
Adrien (Kooda) Ramos


=== License
BSD-2-Clause