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package bjc.utils.dice;
import java.util.Stack;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.FunctionalStringTokenizer;
import bjc.utils.parserutils.ShuntingYard;
/**
* Parse a dice expression from a string
*
* @author ben
*
*/
public class DiceExpressionParser {
/**
* Parse a dice expression from a string
*
* @param exp
* The string to parse an expression from
* @return The parsed dice expression
*/
public IDiceExpression parse(String exp) {
/*
* Create a tokenizer over the strings
*/
FunctionalStringTokenizer fst = new FunctionalStringTokenizer(exp);
/*
* Create a shunter to rewrite the expression
*/
ShuntingYard<String> yard = new ShuntingYard<>();
/*
* Add our custom operators to the yard
*/
yard.addOp("d", 5); // dice operator: use for creating variable
// size dice groups
yard.addOp("c", 6); // compound operator: use for creating compound
// dice from expressions
/*
* Shunt the expression to postfix form
*/
FunctionalList<String> ls = yard.postfix(fst.toList(s -> s),
s -> s);
/*
* Create a stack for building an expression from parts
*/
Stack<IDiceExpression> dexps = new Stack<>();
/*
* Create the expression from parts
*/
ls.forEach((tok) -> {
/*
* Handle compound dice
*/
if (tok.contains("c") && !tok.equalsIgnoreCase("c")) {
String[] strangs = tok.split("c");
dexps.push(new CompoundDice(LazyDice.fromString(strangs[0]),
LazyDice.fromString(strangs[1])));
} else if (tok.contains("d") && !tok.equalsIgnoreCase("d")) {
/*
* Handle dice groups
*/
dexps.push(LazyDice.fromString(tok));
} else {
try {
/*
* Handle scalar numbers
*/
dexps.push(new ScalarDie(Integer.parseInt(tok)));
} catch (NumberFormatException nfex) {
/*
* Apply an operation to two dice
*/
IDiceExpression l = dexps.pop();
IDiceExpression r = dexps.pop();
switch (tok) {
case "+":
dexps.push(new CompoundDiceExpression(l, r,
DiceExpressionType.ADD));
break;
case "-":
dexps.push(new CompoundDiceExpression(l, r,
DiceExpressionType.SUBTRACT));
break;
case "*":
dexps.push(new CompoundDiceExpression(l, r,
DiceExpressionType.MULTIPLY));
break;
case "/":
dexps.push(new CompoundDiceExpression(l, r,
DiceExpressionType.DIVIDE));
break;
case "c":
dexps.push(new CompoundDice(l, r));
break;
case "d":
dexps.push(new LazyDice(l, r));
break;
default:
/*
* Tell the user the operator is invalid
*/
throw new IllegalStateException(
"Detected invalid operator " + tok);
}
}
}
});
/*
* Return the built expression
*/
return dexps.pop();
}
}
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