Help with Algorithm to the code!

[sfe23]

Hi,
I really am trying to write the code. It has been almost a week that I am working on this and I am really stuck.
I am trying to write a code that converts an infix expression into prefix. i.e. 3+4 becomes + 34. I already have the algorithm and I just simply try to convert that into the code but I need help on the part where I need to compare the current operator with the one on top of the stack as you may see in my comments!!

Below is my code:
Nopaste - No description

I truly appreciate your help since this is a part of a way bigger assignment and if I don't do this part I cannot move on!

[angryboy]

what kind of algorithm are you using?

for the record, what i'd did was... reverse the string.
so (A+B)/C becomes: C/(B+A).
then use the shunting-yard algorithm to convert infix 2 postfix, which= CBA+/.
then again, reverse the string, which = /+ABC
(referring to prefix here...)