CODEWITHSUNDEEP
haskell
user266003
user266003

Reputation:

Struggle trying to simplify code

I have the following methods:

mainFunction arg1 = "http://someBaseUrl.com/" ++ arg1
url1 x = mainFunction x ++ "/subUrl1"
url2 x = mainFunction x ++ "/subUrl2"
url3 x = mainFunction x ++ "/subUrl3"
url4 x = mainFunction x ++ "/subUrl4"

My gut tells me that it has to be simplified. But I can't figure out how.

I can't do this, though, because it's not the same:

url1 = (mainFunction .) ++ "/subUrl1"

Your suggestions?

Upvotes: 0

Views: 129

Answers (3)

mb14
mb14

Reputation: 22626

You can do

url s x = mainFunction x ++ s
url1 = url "/subUrl1"
url2 = url "/subUrl2"

etc ...

If you really to write as less code as possible and avoid to call url tree times, you can use this trick (however, I'm not sure it is recommended) 

[url1, url2, url3, url4] = map url ["/subUrl1", "/subUrl2", "subUrl3", "subUrl4"]

This will declare the four functions url1, ... url4.

Upvotes: 5

brooksbp
brooksbp

Reputation: 1986

You can concatenate strings to make your URL. To convert a non-string value to a string, you can use show if it is an instance of Show.

url a b = "http://someBaseUrl.com/" ++ a ++ "/subUrl" ++ (show b)

The url function takes a "string" (list of chars) [Char] and another type 'a' (which is also an instance of Show) and returns a new "string".

Prelude> let url a b = "http://someBaseUrl.com/" ++ a ++ "/subUrl" ++ (show b)
Prelude> url "foo" 3
"http://someBaseUrl.com/foo/subUrl3"
Prelude> :t url
url :: Show a => [Char] -> a -> [Char]

Upvotes: 0

gxtaillon
gxtaillon

Reputation: 1076

Why are you not using a single function with two arguments?

url :: (Show a) => String -> a -> String
url x n = "www" ++ x ++ "/vvv" ++ show n

You should also use Text when dealing with URLs and unicode in general.

Upvotes: 1

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