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https://github.com/idris-lang/Idris2.git
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a972778eab
They don't all pass yet, for minor reasons. Coming shortly... Unfortunately the startup overhead for chez is really noticeable here!
78 lines
2.1 KiB
Idris
78 lines
2.1 KiB
Idris
module Main
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record Point where
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constructor MkPoint
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x : Double
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y : Double
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-- a record creates two projections:
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--
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-- .x : Point -> Double
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-- .y : Point -> Double
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--
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-- because %undotted_record_projections are on by default, we also get:
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--
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-- x : Point -> Double
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-- y : Point -> Double
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-- to prevent cluttering the ordinary name space with short identifiers
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%undotted_record_projections off
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record Rect where
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constructor MkRect
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topLeft : Point
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bottomRight : Point
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-- .topLeft : Rect -> Point
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-- .bottomRight : Rect -> Point
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--
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-- For Rect, we don't get the undotted projections:
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--
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-- Main> :t topLeft
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-- (interactive):1:4--1:11:Undefined name topLeft
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-- Main> :t .topLeft
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-- \{rec:0} => .topLeft rec : ?_ -> Point
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pt : Point
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pt = MkPoint 4.2 6.6
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rect : Rect
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rect =
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MkRect
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(MkPoint 1.1 2.5)
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(MkPoint 4.3 6.3)
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-- New lexical structure:
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--
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-- Foo.bar.baz with uppercase F is one lexeme: NSIdent ["baz", "bar", "Foo"]
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-- foo.bar.baz with lowercase f is three lexemes: foo, .bar, .baz
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-- .foo.bar.baz is three lexemes: .foo, .bar, .baz
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--
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-- If you want Constructor.field, you have to write (Constructor).field.
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--
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-- New syntax of simpleExpr:
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--
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-- Expressions binding tighter than application (simpleExpr),
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-- such as variables or parenthesised expressions,
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-- have been renamed to simplerExpr,
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-- and an extra layer of syntax has been inserted.
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--
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-- simpleExpr ::= (.field)+ -- parses as PRecordProjection
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-- | simplerExpr (.field)+ -- parses as PRecordFieldAccess
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-- | simplerExpr -- (parses as whatever it used to)
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--
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-- (.foo) is a name, so you can use it to e.g. define a function called .foo (see .squared below)
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-- (.foo.bar) is a parenthesised expression
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--
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-- New desugaring rules
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--
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-- (.field1 .field2 .field3) desugars to (\x => .field3 (.field2 (.field1 x)))
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-- (simpleExpr .field1 .field2 .field3) desugars to ((.field .field2 .field3) simpleExpr).
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--
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-- There are more details such as namespacing; see below.
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-- user-defined projections work, too (should they?)
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(.squared) : Double -> Double
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(.squared) x = x * x
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