In Scheme, on can "quote" code, so that it becomes data. Microsoft's F#
and C# 3.0 also have something similar that turns code into "expression
trees". The latter is used extensively in LINQ which translates plain C#
code into SQL code or any other code at runtime (this idea came from FP
I heared)
I can't find something similar for Haskell? Maybe I am looking at the
wrong places?
In Haskell, I know one can use a data constructor as a function (as in
(map Just [1..3])), but a function cannot be turned into a data
constructor (= "quoting"), can it?
Now this is all really fuzzy for a newbie like me, because aren't all
functions initially just data constructors waiting to be evaluated in a
lazy language?
I'm actually looking for something like (loose terminilogy follows)
"context-based-semi-quoting". The idea is to only quote a set of
functions, while evaluating all the others.
For example, in the code
1 `add` 2 `mul` 3
where
add = (+)
mul = (*)
I want to write something like
selectiveQuote [add] (1 `add` 2 `mul` 3)
which would result in an expression tree like
add
/ \
1 6
So the `mul` is not quoted because it is not part of the "context" = [add]
Maybe this is just impossible, I did not dig deep into this.
Thanks,
Peter
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