Cannot bind variables with let

[angerman]

let x = 5

results in

<hint>:3:23: error: parse error on input ‘}’

Using just

x = 5

results in the very helpful message:

<hint>:2:3: error:
    parse error on input ‘=’
    Perhaps you need a 'let' in a 'do' block?
    e.g. 'let x = 5' instead of 'x = 5'

:)

[homam]

Try

let x = 5 in
show x

let 
  f = (* 2)
  x = 5
in
  show $ f x

[angerman]

Sure! That does work. However, x = 5 or let x = 5 would be what would work in ghci, and I probably foolishly expected it to work in HyperHaskell as well.

[HeinrichApfelmus]

Sorry about the confusion. At the moment, only Haskell expressions (as opposed to statements) can be parsed and evaluated. Statements (e.g. let x = …, x <- someIO etc) are planned for Level β.

[HeinrichApfelmus]

As of commit 83d4963 , you can execute monadic statements. In particular, you can introduce new variables with <-, e.g.

test <- return "haskell"

The let statement is not supported just yet.

[HeinrichApfelmus]

The let statement is now supported in version 0.2.1.0.