[Haskell-cafe] Re: A Monad for on-demand file generation?

Joachim Breitner mail at joachim-breitner.de
Thu Jul 3 09:55:52 EDT 2008


Am Mittwoch, den 02.07.2008, 16:43 +0100 schrieb ChrisK:
> > hen, the readFileOD could put the timestamp
> > of the read file in a Monad-local state and the writeFileOD could, if
> > the output is newer then all inputs listed in the state, skip the
> > writing and thus the unsafeInterleaveIO’ed file reads are skipped as
> > well, if they were not required for deciding the flow of the program.
> How is your system similar to make/Makefile or different to
> make/Makefile ?
> Are your actions more restricted?  Are the semantics more imperative?  Are the 
> dependencies still explicit or are them implicit and inferred?

I think the biggest difference is that with Make, you have to explicitly
list all dependencies, which is what I want to avoid by having the Monad
keep record of the used files. So it’s mostly a convenience thingy,
altough a monad would be generally more flexible, e.g. deciding the
output file name based on some content of the some of the input files.

I have some code that I’ll put somewhere soon.


Joachim Breitner
  e-Mail: mail at joachim-breitner.de
  Homepage: http://www.joachim-breitner.de
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