How to use two let's on the same line?

Question

I'm using Hugs interpreter and I want to execute the following code (by Haskell 2010 language report):

let x = 1
z = x+y
in z+1

Is it possible only creating a .hs file and loading? Can I do it by command line directly?

Isolated

Indent the z =... line so that the z lines up under the x. Use spaces, tabs can cause problems in Haskell. – Irvinirvine

doesn't ` let x = 1 in let z = x+y in z + 1` or let x=1; z=x+y in z + 1 work? (I can only test in ghci and basically have no clue about hugs - sorry) – Giaimo

Hugs hasn't been maintained in years. Only a handful of people still use it. Why do you? – Carbone

@Carsten booth works. Thanks! – Isolated

@Isolated I added it as an answer - I hope you don't mind – Giaimo

@Carbone it's probably the FP101xGate thing ;) – Giaimo

Answer 1

Even if you cannot enter multi-line statements into hugs in this case it is possible to do it all in one line.

You can use two let ... in ... like this:

let x = 1 in let z = x+y in z + 1

or you can use ; for multiple definitions like this:

let x=1; z=x+y in z + 1

Giaimo

Answer 2

(Sorry - didn't realize your question was about hugs not ghci.)

You can use :{ in ghci to enter a multiline expression:

shell$ ghci
GHCi, version 7.10.2: http://www.haskell.org/ghc/  :? for help
Prelude> :{
Prelude|   let z = 1
Prelude|       w = 3
Prelude|   in z + w
Prelude| :}
4
Prelude>

Cosmonautics

Why is it sad for hugs to declare lets? (:{) – Schutt