private static bool TryReadHatPower(string text, ref int pos, out int power)
{
if (text[pos] != '^')
{
// leaving this even if it is a try method. Getting here means something should have been checked before
throw new InvalidOperationException("Check that there is a hat power to read before calling this");
}
pos++;
WhiteSpaceReader.TryRead(text, ref pos);
var ps = OperatorReader.TryReadSign(text, ref pos);
if (ps == Sign.None)
{
ps = Sign.Positive;
}
if (OperatorReader.TryReadSign(text, ref pos) != Sign.None)
{
// not allowing a^--2 as it is most likely a typo
power = 0;
return(false);
}
WhiteSpaceReader.TryRead(text, ref pos);
if (IntReader.TryReadInt32(text, ref pos, out power))
{
power *= (int)ps;
return(true);
}
power = 0;
return(false);
}
internal static bool TryRead(string text, ref int pos, out IReadOnlyList <SymbolAndPower> result)
{
var start = pos;
var sign = Sign.Positive;
List <SymbolAndPower> saps = null;
while (pos < text.Length)
{
WhiteSpaceReader.TryRead(text, ref pos);
if (!TryRead(text, ref pos, out SymbolAndPower sap))
{
pos = start;
result = null;
return(false);
}
if (sap.Power < 0 &&
sign == Sign.Negative)
{
pos = start;
result = null;
return(false);
}
if (sign == Sign.Negative)
{
sap = new SymbolAndPower(sap.Symbol, -1 * sap.Power);
}
if (saps == null)
{
saps = new List <SymbolAndPower>();
}
saps.Add(sap);
var op = OperatorReader.TryReadMultiplyOrDivide(text, ref pos);
if (op != MultiplyOrDivide.None)
{
WhiteSpaceReader.TryRead(text, ref pos);
if (OperatorReader.TryReadMultiplyOrDivide(text, ref pos) != MultiplyOrDivide.None)
{
pos = start;
result = null;
return(false);
}
if (op == MultiplyOrDivide.Division)
{
if (sign == Sign.Negative)
{
pos = start;
result = null;
return(false);
}
sign = Sign.Negative;
}
}
}
if (saps == null || !IsUnique(saps))
{
result = null;
return(false);
}
result = saps;
return(true);
}
internal static bool TryReadInt32(string text, ref int pos, out int result)
{
if (pos == text.Length)
{
result = 0;
return(false);
}
var sign = OperatorReader.TryReadSign(text, ref pos);
var start = pos;
var end = Math.Min(text.Length, pos + MaxDigits - 1);
result = 0;
while (pos < end)
{
var c = text[pos] - '0';
if (c < 0 || c > 9)
{
break;
}
result *= 10;
result += c;
pos++;
}
if (pos == start)
{
if (sign != Sign.None)
{
pos--;
}
return(false);
}
if (pos < end ||
!IsDigit(text, pos))
{
switch (sign)
{
case Sign.Negative:
result = -result;
return(true);
case Sign.None:
case Sign.Positive:
return(true);
default:
throw new InvalidEnumArgumentException(nameof(sign), (int)sign, typeof(Sign));
}
}
// getting here means we must handle the last digit and potential overflows.
long temp = result;
temp *= 10;
temp += text[pos] - '0';
switch (sign)
{
case Sign.Negative:
{
temp = -temp;
if (temp >= int.MinValue)
{
result = (int)temp;
pos++;
return(true);
}
pos = start - 1;
result = 0;
return(false);
}
case Sign.None:
case Sign.Positive:
{
if (temp <= int.MaxValue)
{
result = (int)temp;
pos++;
return(true);
}
pos = start - sign == Sign.Positive
? 1
: 0;
result = 0;
return(false);
}
default:
throw new InvalidEnumArgumentException(nameof(sign), (int)sign, typeof(Sign));
}
}