C++ Programming

Write a function named evaluate that accepts an input stream and an output stream as parameters. The input stream represents an input file containing a series of tokens representing a numeric expression involving addition and subtraction and that returns the value of the expression. For example, if an input stream called data contains the following tokens: 4.23.4-4.1 The call of evaluate(data, cout); should evaluate the result as (4.2+3.4-4.1) = (7.6-4.1) 3.5 and should return this value as its result. Every expression will begin with a real number and then will have a series of operatorumber pairs that follow. The operators will be either + (addition) or (subtraction). As in the example above, there will be spaces separating numbers and operators. You may assume the expression is legal Your function should evaluate operators sequentially from left to right. For example, for this expression: 7.5-4.25 2.0 Your function should evaluate the operators as 7.5-4.25-2.0-(7.5-4.25)-2.0 = 3.25- 2.0= 1.25. The input stream might contain just a number, in which case your function should return that number as its result