[Haskell-beginners] Do I understand this well

[Lyndon Maydwell]

Top-level bindings are done in ghci with let:

let (x, y) = addVectors (3.0, 4.5, -3.4, -5.6)

On Mon, Jun 27, 2011 at 11:49 PM, Roelof Wobben <rwobben at hotmail.com> wrote:
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> ________________________________
>> Date: Mon, 27 Jun 2011 16:14:28 +0100
>> Subject: Re: [Haskell-beginners] Do I understand this well
>> From: colinpauladams at gmail.com
>> To: rwobben at hotmail.com
>>
>> No.
>>
>> You are onfusing defining a function with using it.
>>
>>
>> addVectors (x1, y1) (x2, y2) = (x1 + x2, y1 + y2)
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>> defines the function addVectors
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>> (x, y) = addVectors (3.0, 4.5, -3.4, -5.6)
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>> calls the function, and binds x and y to the components of the result
>> (pattern matching).
>>
>> Alternatively:
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>> fst . addVectors (3.0, 4.5, -3.4, -5.6)
>>
>> will return the x-compnent of the result (by composing functions)
>>
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> Oke,
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> I understand that I think
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> But when I ghci I enter :
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> (x, y) = addVectors (3.0, 4.5, -3.4, -5.6)
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> after I made a file with the file defenition.
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> I get this error :
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> :1:7 parse error on input =
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> So something is not right here.
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> Roelof
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