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Monads/Writer monad: Difference between revisions

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Revision as of 22:21, 7 October 2019

425 bytes removed ,  4 years ago
m
→‎{{header|Factor}}: bug fix rolled into release; workaround no longer required
(Add Factor)
m (→‎{{header|Factor}}: bug fix rolled into release; workaround no longer required)
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=={{header|Factor}}==
{{works with|Factor|0.99 2019-10-06}}
Factor comes with an implementation of Haskell-style monads in the <code>monads</code> vocabulary. Due to what may be a bug, the log reads backward. This can be rectified by redefining the <code>writer</code> method for <code>>>=</code> to say <code>prepend</code> instead of <code>append</code>. I will run this by the language maintainers and hopefully the redefinition can be removed in the future.
Factor comes with an implementation of Haskell-style monads in the <code>monads</code> vocabulary.
<lang factor>USING: kernel math math.functions monads prettyprint sequences ;
FROM: monads => do ;
 
{
M: writer >>=
[ run-writer ] curry
[ dip [ run-writer ] compose dip prepend <writer> ] curry ;</lang>
Now we can get on with it:
<lang factor>{
[ 5 "Started with five, " <writer> ]
[ sqrt "took square root, " <writer> ]
Chunes
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