package jscl.text;
import java.util.Arrays;
import java.util.List;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import jscl.math.Generic;
import jscl.text.msg.Messages;
public class Identifier implements Parser<String> {
public static final Parser<String> parser = new Identifier();
private final static List<Character> allowedCharacters = Arrays.asList('√', '∞', 'π', '∂', '∏', 'Σ', '∫');
private Identifier() {
}
private static boolean isValidFirstCharacter(char ch) {
return Character.isLetter(ch) || allowedCharacters.contains(ch);
}
private static boolean isValidNotFirstCharacter(@Nonnull String string, @Nonnull MutableInt position) {
final char ch = string.charAt(position.intValue());
return Character.isLetter(ch) || Character.isDigit(ch) || ch == '_';
}
// returns getVariable/constant getName
@Nonnull
public String parse(@Nonnull Parameters p, @Nullable Generic previousSumElement) throws ParseException {
int pos0 = p.position.intValue();
ParserUtils.skipWhitespaces(p);
final StringBuilder result;
if (p.position.intValue() < p.expression.length() && isValidFirstCharacter(p.expression.charAt(p.position.intValue()))) {
result = new StringBuilder();
result.append(p.expression.charAt(p.position.intValue()));
p.position.increment();
} else {
throw ParserUtils.makeParseException(p, pos0, Messages.msg_5);
}
while (p.position.intValue() < p.expression.length() && isValidNotFirstCharacter(p.expression, p.position)) {
result.append(p.expression.charAt(p.position.intValue()));
p.position.increment();
}
return result.toString();
}
}