[Haskell-beginners] Homework help - calculator function
social_media at abv.bg
Wed Jun 22 22:38:21 CEST 2011
I have a homework which is very important to be done but I can't complete the task at all. The program i should write is: Make 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
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 name = ... where the site stands blank corresponding value. 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;
part , if
any . Variables
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"]. Thank you an advance!
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