/// <summary>
/// Converts a string to a number (used in type coercion).
/// </summary>
/// <returns> The result of parsing the string as a number. </returns>
internal static double CoerceToNumber(string input)
{
var reader = new System.IO.StringReader(input);
// Skip whitespace and line terminators.
while (IsWhiteSpaceOrLineTerminator(reader.Peek()))
{
reader.Read();
}
// Empty strings return 0.
int firstChar = reader.Read();
if (firstChar == -1)
{
return(0.0);
}
// The number can start with a plus or minus sign.
bool negative = false;
switch (firstChar)
{
case '-':
negative = true;
firstChar = reader.Read();
break;
case '+':
firstChar = reader.Read();
break;
}
// Infinity or -Infinity are also valid.
if (firstChar == 'I')
{
string restOfString1 = reader.ReadToEnd();
if (restOfString1.StartsWith("nfinity", StringComparison.Ordinal) == true)
{
// Check the end of the string for junk.
for (int i = 7; i < restOfString1.Length; i++)
{
if (IsWhiteSpaceOrLineTerminator(restOfString1[i]) == false)
{
return(double.NaN);
}
}
return(negative ? double.NegativeInfinity : double.PositiveInfinity);
}
}
// Return NaN if the first digit is not a number or a period.
if ((firstChar < '0' || firstChar > '9') && firstChar != '.')
{
return(double.NaN);
}
// Parse the number.
NumberParser.ParseCoreStatus status;
double result = NumberParser.ParseCore(reader, (char)firstChar, out status, allowHex: true, allowOctal: false);
// Handle various error cases.
switch (status)
{
case ParseCoreStatus.NoDigits:
case ParseCoreStatus.NoExponent:
return(double.NaN);
}
// Check the end of the string for junk.
string restOfString2 = reader.ReadToEnd();
for (int i = 0; i < restOfString2.Length; i++)
{
if (IsWhiteSpaceOrLineTerminator(restOfString2[i]) == false)
{
return(double.NaN);
}
}
return(negative ? -result : result);
}
