how to refer to an input of a function in haskell

Question

I have a function that takes 4-tuple of type list, in the function I need to refer to the input of the function to do some other stuff such as taking the first element of that tuple or get length of the first element of the 4-tuple my function takes as following

foo (a:_,b:_,c:_,d:_) = do something

in the do some thing part i need to do some comparisons but I need the refer to the input of foo and I don't know how . I went like this

let input = (a:_,b:_,c:_,d:_) in foo input // generates error

Can anyone help me out?

tempestadept · Accepted Answer · 2013-10-14 07:30:31Z

4

You can write

foo args@(a:_,b:_,c:_,d:_) = if bar args then (a,c) else (b,d)

In the second case you get an error because wildcards cannot appear on the right side of binding expression

answered Oct 14, 2013 at 7:30

tempestadept

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2 Comments

user2277918 Over a year ago

I used it like this but not working

zed args@(a:_,b:_,c:_,d:_) =  	if ( length ( get1th ( bar args ) ) == 2 )  		then get1th ( bar args ) 		else get1th ( bar args)

tempestadept Over a year ago

Please show your code. I suppose you have a type error since this is syntactically correct

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