[Haskell-cafe] General Advice Needed ..
Gregory Crosswhite
gcross at phys.washington.edu
Thu Jan 14 12:44:58 EST 2010
Yes. An approach that I have always used that has worked well for me is to keep a list of "tricks" while I am studying. Whenever I get stuck on a practice problem but eventually figure it out (either by simply thinking harder, looking it up, or asking someone for help), I try to identify the missing link that had prevented me from seeing how to do it immediately, and then write it down on my "tricks" list so that I know that I need to keep that trick in mind while I am taking the test.
Cheers,
Greg
On Jan 14, 2010, at 8:53 AM, Ian675 wrote:
>
> thankyou.. that made more sense to me :)
>
> What im doing now is..
> Im still working through the "Craft of Functional Programming" book but I've
> found a site that has solutions to some of the excercise questions. So i'm
> noting them down and trying to make sense of them
>
> Is that a good approach?
>
>
> Henk-Jan van Tuyl wrote:
>>
>> On Thu, 14 Jan 2010 15:38:26 +0100, Ian675 <adam_khan_rfc at hotmail.com>
>> wrote:
>>
>>>
>>> Pretty much yeah.. Im going through the book and things like :
>>>
>>> Define a function rangeProduct which when given natural numbers m and n,
>>> returns the product m*(m+1)*....*(n-1)*n
>>>
>>> I got the solution from my lecture notes but I still dont understand it..
>>>
>>> rangeProduct :: Int -> Int -> Int
>>> rangeProduct m n
>>> | m > n = 0
>>> | m == n = m
>>> | otherwise = m * rangeProduct (m+1) n
>>>
>>
>> I'll try to give a clear explanation of this function:
>>
>>> rangeProduct :: Int -> Int -> Int
>>> rangeProduct m n
>> A function is defined with parameters m and n, both Int; the result of the
>> function is also an Int
>>
>>> | m > n = 0
>> If m > n, the result is 0; the rest of the function definition will be
>> skipped
>>
>>> | m == n = m
>> If m is not larger then n, evalution continues here; if m == n, the result
>> of the function is m
>>
>>
>>> | otherwise = m * rangeProduct (m+1) n
>> If previous predicates were False, this branch is evaluated ("otherwise"
>> is always True); the function calls itself with (m+1) as first parameter
>>
>> The boolean expressions in this function are called "guards"; the right
>> hand side after the first guard that evaluates to True, will give the
>> result of the function.
>>
>> Regards,
>> Henk-Jan van Tuyl
>>
>>
>> --
>> http://Van.Tuyl.eu/
>> http://members.chello.nl/hjgtuyl/tourdemonad.html
>> --
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>
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