private ExpressionType getExpressionType() {
skipWhiteSpace();
for (Pattern p : patternMap.keySet()) {
Matcher expMatch = p.matcher(myInput.substring(myCurrentPosition));
if (expMatch.lookingAt()) return patternMap.get(p);
}
throw new ParserException("Unexpected Character " + currentCharacter());
}
/**
* Converts given string into expression tree.
*
* @param input expression given in the language to be parsed
* @return expression tree representing the given formula
*/
public Expression makeExpression(String input) {
myInput = input;
myCurrentPosition = 0;
Expression result = parseExpression();
skipWhiteSpace();
if (notAtEndOfString()) {
throw new ParserException(
"Unexpected characters at end of the string: " + myInput.substring(myCurrentPosition),
ParserException.Type.EXTRA_CHARACTERS);
}
return result;
}
private Expression parseParenExpression() {
ArrayList<Expression> elements = new ArrayList<Expression>();
Matcher expMatcher = EXPRESSION_BEGIN_REGEX.matcher(myInput);
expMatcher.find(myCurrentPosition);
String commandName = expMatcher.group(1);
myCurrentPosition = expMatcher.end();
while (notAtEndOfString()) {
skipWhiteSpace();
if (currentCharacter() == ')') {
myCurrentPosition++;
return expressionCreator(commandName, elements);
}
elements.add(parseExpression());
}
throw new ParserException(
"Expected close paren, instead found " + myInput.substring(myCurrentPosition));
}