Maurício wrote:

Hi,

This is valid code:

module Main where main = do let a = 3 return ()

That desugars to main = do let a=3 in do return ()

Why isn't this one?

module Main where main = do { let a = 3; return (); };

main = do { let a = 3 in return (); }

Thanks for your help, Maurício

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Maurício writes:

Why isn't this one [valid code]?

module Main where main = do { let a = 3; return (); };

My guess is that the compiler is confused about whether you mean do let a = 3 return () or (your intended): do let a = 3 return () A solution which appears to work with GHCi is: do let {a=3}; return () (Note that you don't need the enclosing {}s (although everybody seem to use them), nor the terminating semicolons (they are for statement separation, not termination - Pascal not C) -- they seem to be harmless, though. -k -- If I haven't seen further, it is by standing in the footprints of giants