Haskell RecordDotSyntax language extension proposal (Accepted)

Re:Haskell RecordDotSyntax language extension proposal (Acce... by pbiggar on Monday September 21, 2020 @10:34AM (#24543944)

My goal isn't to look _exactly_ like C++/etc, but rather to have a fairly natural duality between read and write. You can read with:

    a.b.c.d

but a write is:

    let a = {a with b = { a.b with c = { a.b.c with d = 5 } } } }

which is much much more verbose than the OO/imperative:

    a.b.c.d = 5

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Re:Haskell RecordDotSyntax language extension proposal (Acce... by kqr on Tuesday September 22, 2020 @01:13AM (#24551082)

Yeah, lenses let you do

    a & b.c.d .~ 5

To construct a new version of `a` where those nested fields have the new value 5.

Or for an in-place update in a context where that is allowed,

    a.b.c.d .= 5

The lens concept is incredibly nice.

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