private static int GetNCharOperatorLength(CharacterStream cs) {
// R allows user-defined infix operators. These have the form of
// a string of characters delimited by the ‘%’ character. The string
// can contain any printable character except ‘%’.
if (cs.CurrentChar == '%' && !char.IsWhiteSpace(cs.NextChar)) {
// In case of broken or partially typed operators
// make sure we terminate at whitespace or end of the line
// so in 'x <- y % z' '% z' is not an operator.
int start = cs.Position;
int length;
cs.MoveToNextChar();
while (!cs.IsEndOfStream() && !cs.IsWhiteSpace()) {
if (cs.CurrentChar == '%') {
cs.MoveToNextChar();
length = cs.Position - start;
cs.Position = start;
return length;
}
if (cs.IsAtNewLine()) {
// x <- y %abcd
cs.Position = start;
return 1;
}
cs.MoveToNextChar();
}
}
return Get3CharOrShorterOperatorLength(cs);
}
public static void SkipIdentifier(CharacterStream cs, Func<CharacterStream, bool> isIdentifierLeadCharacter, Func<CharacterStream, bool> isIdentifierCharacter) {
if (!isIdentifierLeadCharacter(cs))
return;
if (cs.IsEndOfStream())
return;
while (!cs.IsWhiteSpace()) {
if (!isIdentifierCharacter(cs))
break;
if (!cs.MoveToNextChar())
break;
}
}
public static string NormalizeWhitespace(this string s) {
if(s == null || s.Length == 0) {
return s;
}
var cs = new CharacterStream(new TextStream(s));
var sb = new StringBuilder();
while (!cs.IsEndOfStream()) {
var current = cs.Position;
cs.SkipWhitespace();
if (cs.Position - current > 0) {
sb.Append(' ');
}
while (!cs.IsEndOfStream() && !cs.IsWhiteSpace()) {
sb.Append(cs.CurrentChar);
cs.MoveToNextChar();
}
}
return sb.ToString().Trim();
}
internal static void SkipWhitespace(CharacterStream cs) {
while (!cs.IsEndOfStream() && cs.IsWhiteSpace()) {
cs.MoveToNextChar();
}
}
internal static int HandleExponent(CharacterStream cs, int start) {
Debug.Assert(cs.CurrentChar == 'E' || cs.CurrentChar == 'e');
bool hasSign = false;
cs.MoveToNextChar();
if (cs.IsWhiteSpace() || cs.IsEndOfStream()) {
// 0.1E or 1e
return 0;
}
if (cs.CurrentChar == '-' || cs.CurrentChar == '+') {
hasSign = true;
cs.MoveToNextChar();
}
int digitsStart = cs.Position;
// collect decimals
while (cs.IsDecimal()) {
cs.MoveToNextChar();
}
if (hasSign && digitsStart == cs.Position)
return 0; // NaN like 1.0E-
// Technically if letter or braces follows this is not
// a number but we'll leave it alone for now.
// TODO: This code is not language specific and yet it currently
// handles complex 'i' as well as R-specific 'L' suffix.
// Ideally this needs to be extended in a way so language-specific
// tokenizer can specify options or control number format.
if (char.IsLetter(cs.CurrentChar) && cs.CurrentChar != 'i' && cs.CurrentChar != 'L') {
return 0;
}
return cs.Position - start;
}