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@jawher jawher/RdpExprParser.java Secret
Created Aug 25, 2013

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public Expression expr() {
return or();
}
public Expression or() {
Expression left = and();
while (found(Token.Type.KEYWORD, "or")) {
String operator = token.text;
Expression right = and();
left = new EOp(operator, left, right);
}
return left;
}
public Expression and() {
Expression left = comp();
while (found(Token.Type.KEYWORD, "and")) {
String operator = token.text;
Expression right = comp();
left = new EOp(operator, left, right);
}
return left;
}
public Expression comp() {
Expression left = add_rem();
if (found(Token.Type.SYM, "<") || found(Token.Type.SYM, "<=")
|| found(Token.Type.SYM, ">") || found(Token.Type.SYM, ">=")
|| found(Token.Type.SYM, "=")) {
String operator = token.text;
Expression right = add_rem();
return new EOp(operator, left, right);
} else {
return left;
}
}
public Expression add_rem() {
Expression left = mul_div();
while (found(Token.Type.SYM, "+") || found(Token.Type.SYM, "-")) {
String operator = token.text;
Expression right = mul_div();
left = new EOp(operator, left, right);
}
return left;
}
public Expression mul_div() {
Expression left = app();
while (found(Token.Type.SYM, "*") || found(Token.Type.SYM, "/") || found(Token.Type.SYM, "%")) {
String operator = token.text;
Expression right = app();
left = new EOp(operator, left, right);
}
return left;
}
public Expression app() {
Expression fn = atom();
List<Expression> args = new ArrayList<Expression>();
while (peek(Token.Type.NUM) || peek(Token.Type.BOOL) || peek(Token.Type.NAME) || peek(Token.Type.SYM, "(")
|| peek(Token.Type.KEYWORD, "not") || peek(Token.Type.KEYWORD, "if")) {
args.add(atom());
}
if (args.isEmpty()) {
return fn;
} else {
return new EAp(fn, args);
}
}
public Expression atom() {
if (found(Token.Type.NUM)) {
return new ENum(Integer.parseInt(token.text));
} else if (found(Token.Type.BOOL)) {
return new EBool(Boolean.parseBoolean(token.text));
} else if (found(Token.Type.NAME)) {
return new EName(token.text);
} else if (found(Token.Type.SYM, "(")) {
Expression expr = expr();
expect(Token.Type.SYM, ")");
return expr;
} else if (found(Token.Type.SYM, "-")) {
Expression operand = atom();
return new EOp("-", operand, null);
} else if (found(Token.Type.KEYWORD, "not")) {
Expression operand = atom();
return new EOp("not", operand, null);
} else if (found(Token.Type.KEYWORD, "if")) {
Expression cond = expr();
expect(Token.Type.KEYWORD, "then");
Expression thenExpr = expr();
expect(Token.Type.KEYWORD, "else");
Expression elseExpr = expr();
return new EIf(cond, thenExpr, elseExpr);
} else {
throw error("Unexpected input");
}
}
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