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Make Fake a monad transformer #32

Merged
merged 5 commits into from
Jun 10, 2021
Merged

Make Fake a monad transformer #32

merged 5 commits into from
Jun 10, 2021

Commits on Jun 10, 2021

  1. Add regex-tdfa, QuickCheck to package.yaml

    @ivanbakel
    ivanbakel committed Jun 10, 2021
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  2. Add FakeT monad transformer 

    This is a use-case that came up in my work, where we were generating
lots of 'Fake' values. The trouble with running 'Fake' is that parsing
YAML and building the cache are very expensive, but all the effort
involved is thrown away after the 'Fake' is run - so it makes sense to
generate as much data as possible all in the same 'Fake'. But if you're
using a monad stack, you would have to put 'Fake' at the bottom - when
instead it makes more sense as a transformer, which can share a single
YAML parser and cache between many 'Fake' runs.

This adds the 'FakeT' monad transformer, and makes 'Fake' a synonym for
@FAKET IO@, preserving as much backwards-compatibility as possible with
functions and pattern synonyms.
    @ivanbakel
    ivanbakel committed Jun 10, 2021
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  3. Add MonadFake class for lifting Fakes 

    Following on from the 'FakeT' transformer, it makes sense to be able to
"lift" the default 'Fake' values into the monad stack, in order to allow
them to actually share the transformer cache and generator. This is done
by the 'MonadFake' class, which comes with an instance for 'FakeT', as
well as some of the other transformers defined in the `transformers`
package.
    @ivanbakel
    ivanbakel committed Jun 10, 2021
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  4. Generalise combinators to FakeT 

    This allows users to use combinators on any 'FakeT', instead of just the
base 'Fake' monad.
    @ivanbakel
    ivanbakel committed Jun 10, 2021
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  5. Add README section about FakeT performance impact

    @ivanbakel
    ivanbakel committed Jun 10, 2021
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