Arc Forum | Can you summarize the principal changes required to work with an immutable cons ...

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2 points by lojic 5951 days ago | link | parent

Can you summarize the principal changes required to work with an immutable cons ? I guess now that the files are versioned (thanks!) I can just do a diff, but if there are extensive changes, it might cause a Lisp newbie to miss the forest for the trees.

4 points by lojic 5951 days ago | link

In ac.scm

 ;; set a pointer to the cons cell, then dereference it as a pointer,
 ;; and bang the new value in the given offset

Hmm... so the fix was to "cast" the immutable cons cell to a mutable cons cell? Glad it works, but I was kind of hoping to learn that the immutable cons cell thing was workable for Arc. I guess I should read up on the MzScheme decision to make it immutable and see what pros/cons are associated with it.

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1 point by soegaard 5950 days ago | link

See Flatt's blog post:

http://blog.plt-scheme.org/2007/11/getting-rid-of-set-car-an...

Further discussions can be found in the mail archive.

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1 point by vegashacker 5950 days ago | link

Here's a post about it: http://blog.plt-scheme.org/2007/11/getting-rid-of-set-car-an...

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