feat: wildcards #1049

brprice · 2023-05-30T00:47:56Z

No description provided.

brprice · 2023-05-30T00:49:06Z

Status: ready for review/merge

brprice · 2023-05-30T10:47:38Z

primer/src/Primer/Core/DSL.hs

 case_ :: MonadFresh ID m => m Expr -> [m CaseBranch] -> m Expr
 case_ e brs = Case <$> meta <*> e <*> sequence brs <*> pure CaseExhaustive

+-- | A non-exhaustive case
+caseFB_ :: MonadFresh ID m => m Expr -> [m CaseBranch] -> m Expr -> m Expr
+caseFB_ e brs fb = Case <$> meta <*> e <*> sequence brs <*> (CaseFallback <$> fb)


We leave case_ alone to avoid churn.

brprice · 2023-05-30T10:49:22Z

primer/src/Primer/API.hs

      viewFallback = case fb of
        CaseExhaustive -> Nothing
+        CaseFallback rhs ->
+          let
+            -- these IDs will not clash with any others in the tree,
+            -- since node IDs in the input expression are unique,
+            -- and don't contain non-numerical characters
+            boxId = nodeId <> "Pwild"
+            patternRootId = boxId <> "B"
+           in
+            Just $
+              Tree
+                { nodeId = boxId
+                , body =
+                    BoxBody . RecordPair Flavor.Pattern $
+                      ( Tree
+                          { nodeId = patternRootId
+                          , body = TextBody $ RecordPair Flavor.PatternWildcard (Name Nothing "_")


It is somewhat odd to render the wildcard match as a text "_" node...
Any better ideas?

We are currently thinking that we should render this as a pattern box, but the contents being a NoBody, with a new flavor of PatternWildcard

We also considered not rending the pattern box at all in this case and going straight into the output. However, we realized that while this might be the nicest solution for the wildcard pattern, it wouldn't mesh well with deep patterns (once we can support them) that have nested wildcard patterns.

We now render it as its own flavor with no body

brprice · 2023-05-30T10:53:33Z

primer/src/Primer/Action.hs

+addCaseBranch :: ActionM m => QualifiedText -> ExprZ -> m ExprZ
+addCaseBranch rawCon ze = case target ze of


In general, all our "add/delete case branches" actions (both high and low level) are (will) be offered/accepted on the case node itself. This feels a bit odd but is I think the best we can do for now, since we don't have the ability to select one branch -- we can only select things in branches or binders in patterns. A different choice would be to give "add" at the root of the wildcard RHS and "delete" at the root of each non-wildcard branch's rhs

primer/src/Primer/Action/Available.hs

This is setup for adding fallback branches / wildcard matches, which will add another constructor to the `CaseFallback'` type (and remove `CaseFallbackUseParams`). BREAKING CHANGE: this changes the AST of primer programs, which affects programs stored in a database and the strongly-typed API. Signed-off-by: Ben Price <[email protected]>

We make three changes: - `transformCaseBranches` now modifies the new (currently trivial) fallback/wildcard branches - define a new `transformNamedCaseBranches` that only modifies the non-fallback branches - define a new `transformNamedCaseBranch` that modifies only one particular branch Signed-off-by: Ben Price <[email protected]>

Signed-off-by: Ben Price <[email protected]>

This means that a pattern match can explicitly match on a subset of the constructors of a type, and give a final "catch-all" branch to match any other constructor. This does not give any extra expressivity, since it is possible to exhaustively list every branch, duplicating the output (since all ADTs are finitely branching). However, this is setup to enable pattern matching on primitives in future work, since primitives are infinitely (or impractically large, but finitely) branching. Note that we expose a new DSL combinator `caseFB_` instead of modifying the existing `case_` to avoid churn and the noise of having `CaseExhaustive` in many places. BREAKING CHANGE: this changes the AST of core primer terms, affecting programs stored in a database and the strongly-typed API. This also adds some new flavors to the OpenAPI. Signed-off-by: Ben Price <[email protected]>

BREAKING CHANGE: this adds a new action, which may show up in `Prog`'s logs, which are visible over the strongly-typed API and in saved databases. Signed-off-by: Ben Price <[email protected]>

BREAKING CHANGE: this expands the OpenAPI Signed-off-by: Ben Price <[email protected]>

Consider a pattern match which has only a falllback branch: `case e of _ -> t`; before this commit, evaluating this would force `e` to WHNF before reducing the `case`; after this commit this will reduce to `t` even if `e` diverges. Note that a case with at least one explict match must still force `e`, so one can recover the old behaviour by writing `case e of C x y z -> t ; _ -> t`, duplicating the `t`; however, this is only possible for non-empty types. We make this design decision so that when a future extension enables deep pattern matching the semantics are more obvious and consistent (since a wildcard is then the same as a pattern variable which happens not to be referenced). Signed-off-by: Ben Price <[email protected]>

As setup for enabling moving to a fallback branch, we introduce a notion of a `BranchMove`. This is currently just the `ValConName` of the branch to move to, but later will have another option to move to the fallback branch. BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

As setup for enabling pattern matching on primitives, we introduce a notion of a `Pattern`. This is currently just a `ValConName` (since all pattern matches are specified up to alpha equivalence by their head constructor) , but later will have another option to be a `PrimCon` naming branches on a primitive type. BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

BREAKING CHANGE: this expands the AST of primer programs, visible in stored databases and via the strongly-typed API; it also adds a new flavor to the OpenAPI. Signed-off-by: Ben Price <[email protected]>

BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

Note that there is no way in our API to say "this action requires an argument, and the argument can be any Int except 3 or 7". Thus when adding a branch to a pattern match of primitive type, we cannot request a frontend to give a branch that does not currently exist. We will give an error if an attempt to add a currently-existing branch is made. It would be possible to augment the API's notion of `FreeInt` and `FreeChar` to include a finite list of illegal entries, but we leave this as a possibility for future work. BREAKING CHANGE: this expands the OpenAPI Signed-off-by: Ben Price <[email protected]>

Previously we emitted it as a TextBody with contents "_". This is a rendering decision that should be left to a frontend. BREAKING CHANGE: this changes the OpenAPI Signed-off-by: Ben Price <[email protected]>

brprice mentioned this pull request May 30, 2023

feat: wildcards hackworthltd/primer-app#917

Closed

brprice commented May 30, 2023

View reviewed changes

primer/src/Primer/Action/Available.hs Show resolved Hide resolved

brprice force-pushed the brprice/wildcards branch 2 times, most recently from ba4cc75 to bc1b6de Compare May 30, 2023 15:31

brprice mentioned this pull request Jun 1, 2023

test: adjust distributions to make duplicates more likely #1053

Merged

brprice force-pushed the brprice/wildcards branch from bc1b6de to fd25c52 Compare June 1, 2023 16:44

brprice requested a review from georgefst June 1, 2023 16:44

brprice force-pushed the brprice/wildcards branch from fd25c52 to 69d75cc Compare June 1, 2023 16:48

brprice added 13 commits June 1, 2023 18:00

refactor: caseBranchName helper

bfc267d

Signed-off-by: Ben Price <[email protected]>

feat!: add a low-level "add branch" action

c33f33a

BREAKING CHANGE: this adds a new action, which may show up in `Prog`'s logs, which are visible over the strongly-typed API and in saved databases. Signed-off-by: Ben Price <[email protected]>

feat!: add low-level delete branch action

3061705

BREAKING CHANGE: this adds a new action, which may show up in `Prog`'s logs, which are visible over the strongly-typed API and in saved databases. Signed-off-by: Ben Price <[email protected]>

feat!: add high-level add/remove case branch action

747db5d

BREAKING CHANGE: this expands the OpenAPI Signed-off-by: Ben Price <[email protected]>

feat!: ability to move into fallback branches

076a26a

BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

feat!: enable pattern matching on terms of primitive type

b7c4767

BREAKING CHANGE: this expands the AST of primer programs, visible in stored databases and via the strongly-typed API; it also adds a new flavor to the OpenAPI. Signed-off-by: Ben Price <[email protected]>

feat!: low-level actions for case on primitives

50b0625

BREAKING CHANGE: this changes actions, which are stored in programs logs. These are visible via the strongly-typed api and in saved databases. Signed-off-by: Ben Price <[email protected]>

brprice force-pushed the brprice/wildcards branch from 69d75cc to 03ffeca Compare June 1, 2023 17:23

brprice mentioned this pull request Jun 1, 2023

FR: Pattern matching wildcards and actions #996

Closed

brprice added 2 commits June 1, 2023 20:07

feat!: render wildcards as NoBody

2037646

Previously we emitted it as a TextBody with contents "_". This is a rendering decision that should be left to a frontend. BREAKING CHANGE: this changes the OpenAPI Signed-off-by: Ben Price <[email protected]>

brprice force-pushed the brprice/wildcards branch from 03ffeca to 2037646 Compare June 1, 2023 19:09

georgefst approved these changes Jun 6, 2023

View reviewed changes

dhess added this pull request to the merge queue Jun 6, 2023

Merged via the queue into main with commit a99aa5e Jun 6, 2023

dhess deleted the brprice/wildcards branch June 6, 2023 10:21

georgefst mentioned this pull request Aug 8, 2023

Wildcard patterns #335

Closed

brprice mentioned this pull request Aug 9, 2023

Pattern-matching on primitive constructors #969

Closed

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feat: wildcards #1049

feat: wildcards #1049

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		addCaseBranch :: ActionM m => QualifiedText -> ExprZ -> m ExprZ
		addCaseBranch rawCon ze = case target ze of

feat: wildcards #1049

feat: wildcards #1049

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