public static long GetExpressionStringValue(
string expressionString,
MathRules rules)
{
long result;
expressionString = expressionString.Trim();
if (Regex.IsMatch(expressionString, @"^\d+$"))
{
result = long.Parse(expressionString);
}
else
{
var topLevelOperatorIndexes = GetTopLevelOperatorIndexes(expressionString);
var termExpressionStrings = GetTermExpressionStrings(
expressionString,
topLevelOperatorIndexes);
var termExpressionStringValues = termExpressionStrings
.Select(s => GetExpressionStringValue(s, rules))
.ToList();
var operators = GetOperators(
expressionString,
topLevelOperatorIndexes);
result = GetExpressionValue(
termExpressionStringValues,
operators,
rules);
}
return(result);
}
public static long GetExpressionValue(
IList <long> termValues,
IList <MathOperator> operators,
MathRules rules)
{
if (termValues.Count != operators.Count + 1)
{
throw new Exception($"Invalid term/operator counts");
}
while (operators.Count > 0)
{
EvaluatePrimaryOperator(termValues, operators, rules);
}
return(termValues[0]);
}
public static void EvaluatePrimaryOperator(
IList <long> termValues,
IList <MathOperator> operators,
MathRules rules)
{
var operatorIndex = 0;
if (rules.IsPerformingAdditionBeforeMultiplication)
{
for (int i = 0; i < operators.Count; i++)
{
var testOperator = operators[i];
if (MathOperator.Addition.Equals(testOperator))
{
operatorIndex = i;
break;
}
}
}
var expressionOperator = operators[operatorIndex];
var leftValue = termValues[operatorIndex];
var rightValue = termValues[operatorIndex + 1];
long resultValue = 0;
if (MathOperator.Addition.Equals(expressionOperator))
{
resultValue = leftValue + rightValue;
}
else if (MathOperator.Multiplication.Equals(expressionOperator))
{
resultValue = leftValue * rightValue;
}
termValues.RemoveAt(operatorIndex);
termValues.RemoveAt(operatorIndex);
termValues.Insert(operatorIndex, resultValue);
operators.RemoveAt(operatorIndex);
}