function trouble not in scope: data constructor

Question

I am trying to write a function removeSpaces that once handed a string it will remove any spaces found within it.
What I got so far is:

import Data.Char
removeSpaces :: [Char] -> [Char]
removeSpaces [] = []
removeSpaces xs = filter isAlpha xs

This however keeps giving me the message "not in scope: data constructor" with the pieces of the string that are before and after any spaces within the String. Any help with this would be great.

It works for me, what version of what compiler/interpreter are you using and what is the exact output? Also `removeSpaces "Hello World!!11!" == "HelloWorld", which may not be what you want. — Paul Visschers
– Paul Visschers, Commented Sep 23, 2013 at 15:05

Alex · Accepted Answer · 2013-09-23 15:01:35Z

2

That function looks fine although you don't need the case for the empty list as filter deals with that case.

import Data.Char
removeSpaces :: [Char] -> [Char]
removeSpaces xs = filter isAlpha xs

Can you give an example of how you are calling the function

answered Sep 23, 2013 at 15:01

Alex

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5 Comments

user2807679 Over a year ago

I am calling the funnction as removeSpaces "no spaces" which should return nospaces, as I understand.

Thomas M. DuBuisson Over a year ago

Are you using GHCi or are you just typing removeSpaces "no spaces" as a top level expression in your file?

Alex Over a year ago

Are you sure you have quotation marks around your string where you call it?

user2807679 Over a year ago

I go into the directory where the script is and use ghci then use :l a2 and type the command in.

user2807679 Over a year ago

It finally worked, it was somehow picking up an older version of the script. I just pasted it into a different file to get around that. Thanks everyone.

Thomas M. DuBuisson · Accepted Answer · 2013-09-23 15:06:55Z

1

It works fine:

$ echo "import Data.Char
> removeSpaces :: [Char] -> [Char]
> removeSpaces [] = []
> removeSpaces xs = filter isAlpha xs" > so.hs

$ ghci so.hs
GHCi, version 7.6.2: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( so.hs, interpreted )
Ok, modules loaded: Main.
*Main> removeSpaces "no spaces"
"nospaces"
*Main>

answered Sep 23, 2013 at 15:06

Thomas M. DuBuisson

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