/// <summary>
/// Calculates a Subtraction of a two ALong absolute values, a.k.a "School" method.
/// </summary>
/// <param name="num1">Minuend</param>
/// <param name="num2">Subtrahend</param>
/// <returns>ALong instance representing a difference between absolute values of minuend and subtrahend.</returns>
private static ALong AbsSub(ALong num1, ALong num2)
{
if (num1 == num2)
{
return(new ALong(0));
}
var big = AMath.Max(Abs(num1), Abs(num2));
var small = AMath.Min(Abs(num1), Abs(num2));
var result = String.Empty;
int carry = 0;
for (int i = 0; i < big.Length(); i++)
{
var n1 = big.GetRNumAtIndex(i);
var n2 = small.GetRNumAtIndex(i);
var ns = n1 - carry;
carry = 0;
if (ns < n2)
{
ns += 10; carry = 1;
}
ns = ns - n2;
result = ns.ToString() + result;
}
return(new ALong(result));
}
/// <summary>
/// Converts string representation of a number in a given base to ALong number.
/// Extension does not check if you provide invalid numbers, e.g. '1010102' in base 2 - you will just get incorrect answer.
/// </summary>
/// <param name="number">String representation of a number</param>
/// <param name="aBase">Base number is presented in</param>
/// <param name="sym">String of symbols used to represent a number.</param>
/// <returns>ALong number</returns>
public static ALong FromArbitraryBase(this string number, int aBase, string sym = null)
{
if (String.IsNullOrEmpty(sym))
{
sym = GetSymbols(aBase);
}
if (aBase < 37)
{
number = number.ToLower();
} // Ignore case if base <= 36
var r = number.Reverse();
var resp = new ALong(0);
var i = 0;
foreach (var c in r)
{
var index = sym.IndexOf(c);
resp = resp + AMath.Pow(new ALong(aBase), i) * index;
i++;
}
return(resp);
}
