/**
* Attempts to parse a syntactic assignment expression from token stream. If parsing fails the
* stream is reset to its initial position.
*
* @param tokens source token stream
* @return Expression object or null if tokens don't form a valid expression
*/
public static Expression parse(TokenStream tokens) {
Position pos = tokens.getPosition();
tokens.pushMark();
Expression expr = BinaryExpression.parse(tokens);
if (expr != null) {
tokens.pushMark();
Expression right = null;
String op = tokens.read().toString();
if (assignmentOperators.containsKey(op)) right = AssignmentExpression.parse(tokens);
tokens.popMark(right == null);
if (right != null) expr = new AssignmentExpression(op, expr, right, pos);
}
tokens.popMark(expr == null);
return expr;
}
/**
* Attempts to parse a break statement from token stream. If parsing fails the stream is reset to
* its initial position.
*
* @param tokens source token stream
* @return BreakStatement object or null if tokens don't form a valid break statement
*/
public static BreakStatement parse(TokenStream tokens) {
Position pos = tokens.getPosition();
tokens.pushMark();
BreakStatement breakStatement = null;
if (tokens.read().toString().equals("break")) {
if (tokens.read().toString().equals(";")) breakStatement = new BreakStatement(pos);
}
tokens.popMark(breakStatement == null);
return breakStatement;
}
/**
* Attempts to parse a parameter list from token stream. If parsing fails the stream is reset to
* its initial position.
*
* @param tokens source token stream
* @return ParameterList object or null if tokens don't form a valid parameter list
*/
public static ParameterList parse(TokenStream tokens) {
int line = tokens.getLine(), column = tokens.getColumn();
tokens.pushMark();
ParameterList paramList = null;
if (tokens.read().toString().equals("(")) {
List<Parameter> params = new LinkedList<Parameter>();
Parameter param = Parameter.parse(tokens);
while (param != null) {
tokens.pushMark();
params.add(param);
param = null;
if (tokens.read().toString().equals(",")) param = Parameter.parse(tokens);
tokens.popMark(param == null);
}
if (tokens.read().toString().equals(")")) paramList = new ParameterList(params, line, column);
}
tokens.popMark(paramList == null);
return paramList;
}