[Haskell-cafe] Couple of questions about *let* within *do*

[Job Vranish]

Yes, and yes :)

For example:

import Data.Char

main = do
  let prompt s = do
      putStrLn s
      getLine
  firstName <- prompt "What's your first name?"
  lastName <- prompt "What's your last name?"
  let bigFirstName = map toUpper firstName
      bigLastName = map toUpper lastName
  putStrLn $ "hey " ++ bigFirstName ++ " " ++ bigLastName ++ ", how are
you?"

- Job

On Tue, Aug 10, 2010 at 12:40 PM, michael rice <nowgate at yahoo.com> wrote:

>
> From: Learn You a Haskell
>
> ===================
>
> Remember let bindings? If you don't, refresh your memory on them by reading
> this section. They have to be in the form of let bindings in expression,
> where bindings are names to be given to expressions and expression is the
> expression that is to be evaluated that sees them. We also said that in list
> comprehensions, the in part isn't needed. Well, you can use them in do
> blocks pretty much like you use them in list comprehensions. Check this out:
>
>
>   import Data.Char
>
>     main = do
>       putStrLn "What's your first name?"
>       firstName <- getLine
>       putStrLn "What's your last name?"
>       lastName <- getLine
>       let bigFirstName = map toUpper firstName
>           bigLastName = map toUpper lastName
>       putStrLn $ "hey " ++ bigFirstName ++ " " ++ bigLastName ++ ", how are
> you?"
>
> ===================
>
> Questions:
>
> 1) Is there an implicit *in* before the last line above?
>
> 2) Within a do "in" the IO monad (or any other monad), can a *let* do
> something like this?
>
>       let x = do   -- in a different monad
>
>
> Michael
>
>
>
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