good first issuelanguage / concrete syntaxshovel-ready
描述
With @dougalm.
A use-case is when binding a large expression to a name, e.g.
x = case stuff of
A -> ...
B -> ...
C -> ...
...
<x only enters scope down here>
Perhaps it would be nicer to write
case stuff of
A -> ...
B -> ...
C -> ...
...
x =^
where =^ is a new lexeme meaning "bind to the previous value in the block". There is also precedent in other languages, especially at a REPL, for a magic identifier that means "the previous value".
Reactions? Discuss!