c++问题，谢谢

不好意思，学了几节课又不知道怎么入手了。。


题目是
In reverse Polish notation the operators follow their operands;
To add 3 and 4, one would write "3 4 +" rather than "3 + 4".
If there are multiple operations, the operator is given immediately after its second operand
The expression written "3 − 4 + 5” would be written "3 4 − 5 +" in RPN: first subtract 4 from 3, then add 5 to that
An advantage of RPN is that it obviates the need for parentheses that are required by infix notation.

* Produce a Reverse Polish Notation calculator that operates on input files.
* First, ask the user for the location of an input file. Open this file.
* Read in the input file, and interpret the input data as RPN. Each new line should be interpreted as its own math problem.
* Display the resulting answers to the screen.
* If a math problem has an error in its syntax, display SYNTAX ERROR for that line and continue with the next problem.
* Do not support unary operators.
* Add support for the following operators, written exactly as shown: + - * / % pow
* Math problems are guaranteed to not have more than 5 total operands. As a result, you do not need to use arrays (which we have not yet covered).

Sample Input:
3 4 5.0 * −
7
4. * 8 30 +
banana
9 10 + 30 -

Sample Output:
-17
7
SYNTAX ERROR
SYNTAX ERROR
-11



一开始需要输入文件的位置，然后根据这个地址来读取这个文件。。。用户输入file location（比如c:\Download\abc.txt）后不知道怎么写code来调用了。。。我只会ifstream myfile ("C:\\Users\\Daniel\\Documents\\Visual Studio 2012\\Projects\\Lab2\\Lab2\\input.txt");这种已知地址的调用。。。长长的一串地址不知道怎么用ifstream调用。。。

接下来调用文件中每个数字符号，然后分析计算，我应该能够写出来，就是一开始怎么根据用户输入的地址调用文件不会，有大神帮我一下吗？

谢谢