/**
* When the name of this ParserExtension is encountered by a parser with which the extension is
* registered, the parser calls this routine to parse the summation subexpression. The
* subexpression has the form (<variable>,<lower-limit>,<upper-limit>,<expression>). This method
* is not meant to be called directly
*/
public void doParse(Parser parser, ParserContext context) {
int tok = context.next();
String open = context.tokenString;
if (tok == ParserContext.OPCHARS
&& (open.equals("(")
|| (open.equals("[") && (context.options & Parser.BRACKETS) != 0)
|| (open.equals("{") && (context.options & Parser.BRACES) != 0))) {
String close = open.equals("(") ? ")" : (open.equals("[") ? "]" : "}");
tok = context.next(); // Must be an identifier.
if (tok != ParserContext.IDENTIFIER)
throw new ParseError(
"Expected the summation variable as the first argument of " + name + ".", context);
String varName = context.tokenString;
tok = context.next();
if (tok != ParserContext.OPCHARS || !context.tokenString.equals(","))
throw new ParseError(
"Exprected a comma after the index variable, " + varName + ".", context);
parser.parseExpression(context);
tok = context.next();
if (tok != ParserContext.OPCHARS || !context.tokenString.equals(","))
throw new ParseError(
"Exprected a comma after the lower limit expression for " + name + ".", context);
parser.parseExpression(context);
tok = context.next();
if (tok != ParserContext.OPCHARS || !context.tokenString.equals(","))
throw new ParseError(
"Exprected a comma after the upper limit expression for " + name + ".", context);
Variable v = new Variable(varName);
context.mark(); // Temporoarily add the summation variable to the symbol table.
context.add(v);
ExpressionProgram saveProg = context.prog;
context.prog = new ExpressionProgram(); // Compile the expression into a new program.
parser.parseExpression(context);
tok = context.next();
if (tok != ParserContext.OPCHARS || !context.tokenString.equals(close))
throw new ParseError(
"Expected a \"" + close + "\" at the end of the paramter list for " + name + ".",
context);
context.revert(); // Restore the state of the ParserContext.
saveProg.addCommandObject(new Cmd(v, context.prog));
context.prog = saveProg;
} else throw new ParseError("Parentheses required around parameters of summation.", context);
} // end doParse()
