Implement pattern guards #1910
Merged
Implement pattern guards #1910
Conversation
This file contains 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 commit implement pattern guards, which are side conditions that can
be added to the branch of a match expression, following the pattern, to
further constrain the matching. This condition is introduced by the
(already existing) `if` keyword. For example:
`match { {list} if list != [] => body }` will match a record with a
unique field `list` that isn't empty.
The compilation is rather straightforward, as a pattern is already
compiled to a tree of if-then-else while also building the bindings
introduced by pattern variables. After all the conditions coming from
the pattern have been tested, we just additionally check for the guard
(injecting the bindings in the condition since the guard can - and most
often does - use variables bound by the pattern).
jneem
reviewed
May 9, 2024
Co-authored-by: jneem <joeneeman@gmail.com>
jneem
approved these changes
May 13, 2024
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Outdated suggestions cannot be applied.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.
This PR implements pattern guards, which are side conditions that can be added to the branch of a match expression, following the pattern, to further constrain the matching. A guard is introduced by the (already existing)
ifkeyword. For example:The compilation is rather straightforward, as a pattern is already compiled to a tree of if-then-else while also building the bindings introduced by pattern variables. After all the conditions coming from the pattern have been tested, we just additionally check for the guard (injecting the bindings in the condition since the guard can - and most often does - use variables bound by the pattern).
I expect this feature to be particularly nice for writing custom contracts, which are currently in practice sizeable nested if-then-else trees, which could hopefully be aggressively flattened with patterns and guards.