Stack Demonstration w/ Parens

Stack Operation Demonstration Program w/ Parens

An parenthetic expression is evaluated as follows.

The expression is scanned from left to right.
If an opening paren is encountered, it is pushed onto the stack.
If a closing paren is encountered, it is compared to the top opening paren on the stack. If they correspond, the applet continues. If they do not, the applet finishes with a message that the expression is unacceptable.
When you provide an expression to be evaluated, separate chars with spaces as in [ ( ) [ ( ) ] ],