Hi,
Andreas Abel wrote:
To your amusement, I found the following in the Agda source:
abstractToConcreteCtx :: ToConcrete a c => Precedence -> a -> TCM c
abstractToConcreteCtx ctx x = do
scope <- getScope
let scope' = scope { scopePrecedence = ctx }
return $ abstractToConcrete (makeEnv scope') x
where
scope = (currentScope defaultEnv) { scopePrecedence = ctx }
I am surprised this is a legal form of shadowing. To understand which
definition of 'scope' shadows the other, I have to consult the formal
definition of Haskell.
Isn't this just an instance of the following, more general rule:
To understand what a piece of code means, I have to consult the formal
definition of the language the code is written in.
In the case you cite, you "just" have to desugar the do notation
abstractToConcreteCtx :: ToConcrete a c => Precedence -> a -> TCM c
abstractToConcreteCtx ctx x =
getScope >>= (\scope ->
let scope' = scope { scopePrecedence = ctx } in
return $ abstractToConcrete (makeEnv scope') x)
where
scope = (currentScope defaultEnv) { scopePrecedence = ctx }
and it becomes clear by the nesting structure that the lambda-binding
shadows the where-binding. It seems that if you argue against this case,
you argue against shadowing in general. Should we adopt the Barendregt
convention as a style guide for programming?
Tillmann
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