https://github.com/gelisam/hs-promote

C++-style type promotion for Haskell's numeric hierarchy
https://github.com/gelisam/hs-promote

Last synced: 22 days ago
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C++-style type promotion for Haskell's numeric hierarchy

• Host: GitHub
• URL: https://github.com/gelisam/hs-promote
• Owner: gelisam
• Created: 2013-03-31T20:47:04.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2015-04-22T00:10:47.000Z (over 9 years ago)
• Last Synced: 2023-04-13T07:57:02.778Z (over 1 year ago)
• Language: Haskell
• Size: 137 KB
• Stars: 2
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
Type promotion in haskell

=========================

Like in Haskell, the arithmetic operations of C++ always act on identical types (ex: 2 + 2 or 2.0 + 2.0, but not 2 + 2.0).

Unlike Haskell, C++ automatically promotes the arguments of arithmetic operations to the most general type. Lest it be thought that C++ is superior to Haskell in this regard, here is an implementation of type promotion in Haskell.

Implementation

--------------

I use type families to compute the resulting type, e.g. Promote Int Double = Double because the result of 2 + 2.0 is a Double.

One downside of this implementation strategy is that we need to define a quadratic number of instances, one for each pair of compatible types. To avoid doing this, I use Template Haskell to generate all the instances.