Hi Alexander,

You could quote the whole do-block:

> $(strictify [| do y .= x; ... |])

And then strictify :: ExpQ -> ExpQ manipulates the AST a bit: x .= y does parse as an expression, so you can change a NoBindS containing that .= function into a BindS or LetS. Unfortunately the quotes built into TH complain about undefined variables, so you'll probably have to use a quasiquote instead (haskell-src-meta can help here).

Also, you may want to desugar to "let !x = y `deepseq` y", or involve (return $!) since "let x = y `deepseq` y where y = undefined :: Int" only crashes when you seq the x.

Adam

On Wed, Feb 5, 2014 at 7:37 AM, Alexander Alexeev <mail@eax.me> wrote:

Hello!

I'm wondering, is there any way to declare assignment operators
in Haskell? For example, strict assignment operators:

x .= y -- equals: let x = y `deepseq` y
x := y -- equals: x <- y `deepseq` y

As far as I can tell, Template Haskell is not able to do anything like
this, because I can't event quote expressions like `let x = y` or `x <-
y`. Is there any other way (plugin for GHC, etc)? Or maybe I'm doing
something wrong and TH is quite able to handle this task?

I'm pretty sure that I could use a preprocessor, but I wonted to find
a better solution.

--
Best regards,
Alexander Alexeev
http://eax.me/
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