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This page is used to discuss _minor_ tweaks to the existing record system if it is decided that it will be left in basically unchanged. radical or brand new record systems should be discussed elsewhere.
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This page is used to discuss _minor_ tweaks to the existing record system if it is decided that it will be left in basically unchanged. radical or brand new record systems should be discussed elsewhere.
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- reallow punning, Foo {x,y,z} would be interpreted as Foo {x = x, y = y, z = z} in both declaration and pattern matching contexts.
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- update syntax should not bottom out when fields are undefined. as in
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```wiki
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data Foo = Foo { x :: String, y :: Int } | Bar { x :: String }
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foo = Bar { x = "hello }
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baz = foo { y = 3 }
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should not result in an error, but rather pass foo through unchanged. update should update the record if it exists, but pass the type through otherwise.
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this would make the update syntax actually useful
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```
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- label-based pattern matching
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the function:
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```wiki
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f val { x = "foo" } = 4
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```
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should match if passed a Foo or a Bar with x being equal to "foo" and val would be bound to its argument (like an @ pattern)
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```wiki
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g _ { y = 3 } = 4
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```
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would match only the Bar constructor since it is the only one with a y field.
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This would mitigate the problems caused by accessors being partial functions since you can use a simple case statement to get the effect of an accesor that returns its result in a Maybe
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- first class update and setting syntax (more advanced, needs better syntax)
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A syntax for updating and setting fields should be allowed.
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some possibilites are
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```wiki
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foo { x = }
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would be equivalant to (\v -> foo { x = v })
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foo { x \ }
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would be equivalant to
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(\f -> foo { x = case foo of _ {x} -> foo { x = f x }; _ -> foo })
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``` |
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\ No newline at end of file |