Program / Task Name:

   HP Calculator

Level:

 

 Advanced

Point Value:

 

 13

 

Task Description

Some hp calculators, such as the 12c, use an entry system logic called RPN. Sometimes this is called the ‘enter method’ because the calculator has no EQUAL key, but uses an ENTER key instead. Many scientists and engineers prefer this entry system logic. You will write a program to process RPN expressions.

In summary, RPN does not use parentheses, and operators (like plus and minus) follow their operands. A few examples are shown below:

Algebraic Expression

RPN

3 + 5

3 5 +

6 * ( 7 + 8 )

6 7 8 + *

( 9 + 5 ) * ( 7 + 8 )

9 5 + 7 8 + *

( ( 4 * ( 2 – 3 ) ) / ( 5 – 6 )

4 2 3 – * 5 6 – /

Program Input

Each line of the input file (prob12.in) contains a series of numbers and operators. The program must evaluate these lines as RPN expressions. All tokens are separated by one or more spaces. Numbers may be negative. Valid operators are +(addition), -(subtraction), *(multiplication) and /(division). The last line of the file contains only the word END:

16 3 7 + *
4 32.125 13 – * 20 +
5 –3 * 4 2 / 6 3 1 – / + +
END

Program Output

The program will print the computed result of each RPN expression on a separate line.

160
96.5
-10

 

 

   
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