Kotlin - Problems with while()

Question

I was making a calculator in Kotlin and I'm having trouble solving an issue that I'm having with while().On this particular part of the code, I'm trying to find the first operator in the equation, but I need to exclude the ones that indicate whether a number is negative - (or positive +, optional), which need to be indicated between parentheses like so: (-5)

var charay = charArrayOf('+', '-', '*', '/')

var op = 0

var reference = 0

var bol = false

while( bol == false && op != -1){

    println(op)
    println(bol)
    println(bol == false && op != -1)

    op = input.indexOfAny(charay, reference)

    if (!input.get(op - 1).equals('(')){

        bol = true

    }else{

        reference = op + 1
    }

    println(op)
    println(bol)
    println(bol == false && op != -1)
}

To test a normal equation I entered the equation 4+4 and the console looks like this:

0
false
true
1
true
false
0
false
true
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: 
String index out of range: -2
    at java.lang.String.charAt(String.java:658)
    at CalculatorKt.CalculateValue(Calculator.kt:67)
    at CalculatorKt.CalculateValue(Calculator.kt:108)
    at CalculatorKt.main(Calculator.kt:119)

Like I suspected, for some reason, the variables reset at the end of the while(), which is the reason why it never leaves said while(). Can anyone tell me why?

Andy Ray · Accepted Answer · 2017-08-27 02:40:09Z

3

Read the error. You're trying to read the character of a string at an index that doesn't exist with this statement:

input.get(op - 1)

You need to check what op is first to make sure it is found. indexOfAny returns -1 if not found in the string. Because we can't see what charay is, we can't help you further.

answered Aug 27, 2017 at 2:40

Andy Ray

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1 Comment

Migaloco Over a year ago

My bad, still new to this but i hope that I've given you all the information you need now

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