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?

Indent the `z =...` line so that the z lines up under the x. Use spaces, tabs can cause problems in Haskell. — bheklilr, Nov 07 '15 at 14:15
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) — Random Dev, Nov 07 '15 at 14:15
Hugs hasn't been maintained in years. Only a handful of people still use it. Why do you? — dfeuer, Nov 07 '15 at 14:59

ErikR · Answer 1 · 2015-11-07T15:24:29.490

4

(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>

edited Nov 07 '15 at 15:24

answered Nov 07 '15 at 14:26

ErikR

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Why is it sad for hugs to declare `let`s? (`:{`) – Kapol Nov 07 '15 at 15:32

score 4 · Accepted Answer · answered Nov 08 '15 at 07:41

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

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

2 Answers2