# [Haskell-cafe] Homework help - calculator function

SM Design social_media at abv.bg
Wed Jun 22 22:39:30 CEST 2011

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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
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     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;
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"].                    Thank you an advance!
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