Done in Cygwin using g++ compiler

This is a three part project:

• Part one - build a program that:
  • Prompts the user for a string of user input .
  • Treat that string as a mathematical expression in an infix form.
  • Convert the string into a series of tokens where each token is an operator, or a value delimited by whitespace , operator, or
• Part two -
  • Convert to postfix and print out the results. ( or print out an error if badly formed)
• Part Three - further.
  • Do the math to evaluate the expression when all operands are values ( not variables)

For this project the operators you will support are:

Plus +

Minus -

Times *

Divide /

Modula %

When I test the program I would expect to see something like this: ( Bold is what I enter on the command line)

Input an expression: A+ B * 31

Tokens: A + B * 31

Postfix: A B + 31 *

Value: Cannot be calculated

Input and Expression: 3+4*12

Tokens: 3 + 4* 12

Postfix: 3 4 12* +

Value: 51

If the input expression is invalid, print out that fact. Use exceptions to catch any error conditions.

(Note - put a space between each Token for clarity)

How do you look at a string and know what the operands vs operators. IE if the input string is:

A+FRED+23*13-GG OR A + FRED +23* -GG

How do you identify that the tokens are A, FRED, 23, * etc. - and which tokens are operands vs operators?

The easiest way is with a stack.

Put the first character on the stack.

Keep putting characters on until you see an unpend char ( a space) OR an operator or a

Pop the chars off the first stack onto a second

Pop the chars off the second stack ( now they are in proper order)

Pass the token to your infx to postgix code.

If you have an operator.Send that

Repeat until no more characters.