The professor provided us with code and we are suppose to alter it. In order to get the proper outputs. I'm unsure why mines is wrong. It is graded...

The professor provided us with code and we are suppose to alter it. In order to get the proper outputs. I'm unsure why mines is wrong.

It is graded on:

calculator(expr) :The grading script will feed 4 randomly chosen test inputs, each for 1.5 points. One of them will be an input that should cause an error such as "4 */2+5", whose expected returned value is an error message.

findNextOpr(txt): 2 randomly chosen test inputs checking the correct returned values.

isNumber(txt): 2 randomly chosen test inputs checking the correct returned values. 

 getNextNumber(expr, index): 1 randomly chosen test input checking the correct returned value.