/**
* Number parser generates token of type TokenType.Number.
* If successful, 'true' is returned, 'result' contains token, 'next' contains further index information.
* If not successful, 'false' is returned, other values can be arbitrary.
*/
public static bool ParseNumber(string source, int index, out NumberToken result, out int next)
{
result = null;
next = -1;
var index2 = index;
if (index2 >= source.Length)
{
return(false);
}
// parse sign (optional)
if (source[index] == '+' || source[index] == '-')
{
index2++;
}
if (index2 >= source.Length)
{
return(false);
}
// parse unsigned number
var ok = ParseUnsignedNumber(source, index2, out result, out var nnext);
// process result if OK
if (ok)
{
next = nnext;
result._from = index;
}
return(ok);
}
private static bool ParseUnsignedNumber(string source, int index, out NumberToken result, out int next)
{
if (ParseUnsignedReal(source, index, out result, out next))
{
return(AllowedAfterParsedNumber(source, result));
}
if (ParseUnsignedInteger(source, index, out result, out next))
{
return(AllowedAfterParsedNumber(source, result));
}
return(false);
}
private static bool AllowedAfterParsedNumber(string source, NumberToken result)
{
if (result == null)
{
return(false);
}
// check last character if any
if (result._to < source.Length && (
Char.IsLetterOrDigit(source[result._to]) ||
source[result._to] == '_')
)
{
return(false);
}
return(true);
}
private static bool ParseUnsignedReal(string source, int index, out NumberToken result, out int next)
{
// parse digit sequence
var ok = ParseDigitSequence(source, index, DEC, out result, out next);
if (!ok)
{
return(ok);
}
var nextIndex = result._to;
// and maybe .digit sequence
if (nextIndex >= source.Length)
{
return(ok);
}
if (source[nextIndex] == '.')
{
var ok2 = ParseDigitSequence(source, nextIndex + 1, DEC, out var result2, out var nnext);
if (ok2)
{
next = nnext;
nextIndex = result2._to;
}
else
{
return(false);
}
}
// and maybe scale factor
if (nextIndex < source.Length && (source[nextIndex] == 'e' || source[nextIndex] == 'E'))
{
if (ParseScaleFactor(source, nextIndex, out var result3, out var nnnext))
{
next = nnnext;
}
else
{
return(false);
}
}
private static bool ParseControlString(string source, int index, out StringToken result, out int next)
{
if (index >= source.Length || source[index] != '#')
{
result = null;
next = -1;
return(false);
}
var ok = NumberToken.ParseUnsignedInteger(source, index + 1, out var numberToken, out var nnext);
if (ok)
{
result = new StringToken();
result._from = index;
result._to = nnext;
next = nnext;
return(true);
}
result = null;
next = -1;
return(false);
}