Type cases for subtracting 1 from Int>1 producing PosInt #883
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
This should be easy to do with refinement types. Do we think it's worth adding more cases to the numeric tower for? |
|
Okay, I see your point, this slight variation passes using However, is there a way to make it typecheck by default, without the user having to add |
AlexKnauth
force-pushed
the
sub1-int-gt-1
branch
from
c91cdb0 to
4ff0858
Compare
|
I'm still skeptical that we should take this route to more precise typechecking of numeric types, rather than using refinements. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Refines the types of
sub1and(- _ 1)so that if the argument has a positive integer type known greater than 1, the result of subtraction still has a positive integer type.This is useful in cases where a function recurs on a positive integer and treats
1as the base case. In the else case, it's known to not be1, so thesub1should be known to be positive: