I found the library myself, and i already put the code in that site:
http://hpaste.org/48277
That's what i have tried to do for making the task by calling the one
string function by another one:
include kursovazadacha
parse :: [a] -> [a]
parse [] = []
parse (x:xs) = eval (x:xs)
The error from the compiler:
ERROR file:.\list.hs:3 - Syntax error in declaration (unexpected `;',
possibly due to bad layout)
On Fri, Jun 24, 2011 at 11:20 PM, Daniel Patterson
<lists.hask...@dbp.mm.st> wrote:
> What have you tried to do in order to make it work for the list, and what
> error results? What is confusing about the error message? More generally, how
> could you transform an operation on a single string into one that does the
> same thing to a list of strings? You've probably talked about higher order
> functions in your class - would any of the common ones (filter, map, foldr)
> be helpful here? Would any encapsulate what you are trying to do?
>
> If you include these kinds of things, I think you'll find this community to
> be very helpful; without that (showing what your thought process is, why it
> isn't working, what seems confusing about what the haskell compiler is
> telling you, etc), you are not going to get help here. People here are very
> friendly and willing to help people learn; this is not a place to come to get
> an assignment finished :)
>
> Also, could you put the library you are using (I'm assuming that this is
> provided by your university) and the code on somewhere like hpaste.org, so
> that the formatting is not messed up by email, and it is syntax highlighted?
>
> On Jun 24, 2011, at 3:57 PM, Stoyan Peev wrote:
>
>> Hello all,
>>
>> I am experiencing some issues to do my course task in university.
>>
>> I have to write a calculator- function in Haskell. The function
>> argument is a list of strings and also form such list, as each string
>> of the argument made definite action:
>> - If the string has the form of an arithmetic _expression_ - calculate
>> this _expression_. The string result becomes part of the list-result.
>> If the _expression_ contains a variable which is not assigned value,
>> the result is displayed "undefined".
>> - If the string has the form- Name = value calculated from the last
>> _expression_ is assigned to the variable with the corresponding name
>> in the list, and in the result list is formed a string with type
>> - If there is not a calculated _expression_ to be assigned to form a
>> string "no value".
>> - If the string is non-blank, but there is a species different from
>> the above two case, form the string "error".
>> - If the string is empty, incl. when it contains only spaces, in the
>> result there is not form a string.
>>
>> Expressions consist of integers without sign variables, operations +
>> (Addition), - (subtraction), * (multiplication) and / (divide) and
>> parentheses. Where no brackets, the operations are performed from left
>> to right, but * and / precede the + and -. Implementation of any
>> operation gives integer; in the division rejected the fractional part,
>> if any.
>> Variables have names of one letter - from the Latin small letter. In
>> the beginning, end or between the elements of each row can have spaces
>> - they are irrelevant to its correctness.
>> Example: the list-argument
>> ["3 +7 / 2" "2 + x", "= s", "2 * s +4", "", "2 + +4 / 5]
>> function should provide a result-list
>> ["6", "undefined", "s = 6", "16", "error"].
>>
>>
>> I say another person have the same task, but he didn't do anything. I
>> started doing this task myself but i get stuck in the middle. Then i
>> started searching for something that could help me and find out you :)
>>
>> The code i have written so far uses the library file "Parsing.lhs"
>> but what i have written is taking those actions that i already
>> described, only for a string. I cannot modify it to work for list of
>> string, and complete the whole task.
>>
>> I'll be glad to finish the task myself, but i am going to need some help.
>>
>> Here is the code i have already written:
>>
>>
>> import Parsing
>>
>> expr :: Parser Int
>> expr = do t <- term
>> do symbol "+"
>> e <- expr
>> return (t+e)
>> +++ do symbol "-"
>> e <- expr
>> return (t-e)
>> +++ return t
>> term :: Parser Int
>> term = do f <- factor
>> do symbol "*"
>> t <- term
>> return (f * t)
>> +++ do symbol "/"
>> t <- term
>> return (f-t)
>> +++ return f
>> factor :: Parser Int
>> factor = do symbol "("
>> e <- expr
>> symbol ")"
>> return e
>> +++ natural
>> eval :: String -> Int
>> eval xs = case (parse expr xs) of
>> [(n,[])] -> n
>> [(_,out)] -> error ("undefined")
>> [] -> error "error"
>>
>>
>>
>> Thanks all in advance :)
>>
>> --
>> Best Wishes
>> Stoyan Peev
>>
>> _______________________________________________
>> Haskell-Cafe mailing list
>> Haskell-Cafe@haskell.org
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
>
--
Поздрави,
Стоян Пеев
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