func findUnaryMinus(exprTokens) {
    index = 0
    toReturn = []

    while index < len(exprTokens) {
        token = exprTokens[index] // e.g ('number', '5')

        if token.TYPE is 'operator' {
            if token.VALUE is '-' {
                if index == 0 OR exprTokens[index-1].VALUE is "("
                    OR exprTokens[index-1].TYPE is 'operator' {

                    // These are the three rules for unary minus ^^
                    toReturn += "_"
                    // replace '-' with '_' to represent unary minus
                } else toReturn += token
            } else toReturn += token
        } else toReturn += token

        index += 1
    }
}