static void Main(string[] args)
{
// match 0+ whitespace, then mixed fraction or [im]proper fraction or whole number followed by space
string fractionPattern = @"\s*((?<whole>\d+)_(?<num>\d+)/(?<denom>\d+)|(?<num>\d+)/(?<denom>\d+)|(?<whole>\d+\s*))";
// match 0+ whitespace then any of 4 allowed operators
string operatorPattern = @"\s*(?<oper>[\+\*-/])";
Regex queryPattern = new Regex(@"
\s* # match zero or more whitespace characters, then ...
[\?] # match query operator, then ...
(?<remainder>.*) # rest of input
", RegexOptions.IgnorePatternWhitespace);
long whole, num, denom;
Fraction first;
Console.WriteLine("Enter a math expression using whole numbers, fractions and operators. Begin with '?' symbol.");
Console.WriteLine("Valid operators are +, -, *, /.");
Console.WriteLine("Valid operands are whole numbers (x), mixed fractions (x_x/x), and proper/improper fractions (x/x).");
Console.WriteLine("If '?' symbol is omitted, or syntax error occurs, program ends.");
while (true)
{
string input = Console.ReadLine();
// verify query symbol included
MatchCollection mc = queryPattern.Matches(input);
if (mc.Count == 0)
{
Console.WriteLine("Query symbol '?' missing.");
break;
}
// get first whole number or fraction
input = mc[0].Groups["remainder"].Value;
string firstFractionPattern = fractionPattern + @"(?<remainder>.*)";
Regex firstRegex = new Regex(firstFractionPattern);
mc = firstRegex.Matches(input);
if (mc.Count == 0)
{
Console.WriteLine("First operand incorrectly specified.");
break;
}
long.TryParse(mc[0].Groups["whole"].Value, out whole);
long.TryParse(mc[0].Groups["num"].Value, out num);
long.TryParse(mc[0].Groups["denom"].Value, out denom);
first = new Fraction(whole, num, denom == 0 ? 1 : denom);
input = mc[0].Groups["remainder"].Value;
// Get rest of operators and whole number/fractions
string opFractionPattern = operatorPattern + fractionPattern;
Regex restRegex = new Regex(opFractionPattern);
mc = restRegex.Matches(input);
if (mc.Count == 0)
{
Console.WriteLine("Invalid expression found.");
break;
}
//Calculate output result
first.convert();
foreach (Match m in mc)
{
string oper = m.Groups["oper"].Value;
long.TryParse(m.Groups["whole"].Value, out whole);
long.TryParse(m.Groups["num"].Value, out num);
long.TryParse(m.Groups["denom"].Value, out denom);
Fraction next = new Fraction(whole, num, denom == 0 ? 1 : denom);
next.convert();
switch (oper)
{
case "+":
first.add(next);
break;
case "-":
first.subtract(next);
break;
case "*":
first.multiply(next);
break;
case "/":
first.divide(next);
break;
}
}
first.writeResult();
}
}
