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package bjc.utils.dice.ast;
import org.apache.commons.lang3.StringUtils;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.FunctionalStringTokenizer;
import bjc.utils.parserutils.AST;
import bjc.utils.parserutils.ShuntingYard;
import bjc.utils.parserutils.TreeConstructor;
/**
* Create an AST from a string expression
*
* @author ben
*
*/
public class DiceASTParser {
/**
* The yard to use for shunting expressions
*/
private static ShuntingYard<String> yard;
static {
yard = new ShuntingYard<>();
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
yard.addOp(":=", 0); // binding operator: Bind a name to a variable
// expression
}
/**
* Build an AST from a string expression
*
* @param exp
* The string to build from
* @return An AST built from the passed in string
*/
public AST<IDiceASTNode> buildAST(String exp) {
FunctionalList<String> tokens =
FunctionalStringTokenizer.fromString(exp).toList((s) -> s);
FunctionalList<String> shunted = yard.postfix(tokens, (s) -> s);
AST<String> rawAST =
TreeConstructor.constructTree(shunted, this::isOperator);
AST<IDiceASTNode> bakedAST = rawAST.transmuteAST((tok) -> {
if (isOperator(tok)) {
return OperatorDiceNode.fromString(tok);
} else if (isLiteral(tok)) {
return new LiteralDiceNode(tok);
} else {
return new VariableDiceNode(tok);
}
});
return bakedAST;
}
/**
* Check if a token represents a literal
*
* @param tok
* The token to check
* @return Whether or not the token represents a literal
*/
private static boolean isLiteral(String tok) {
if (StringUtils.countMatches(tok, 'c') == 1
&& !tok.equalsIgnoreCase("c")) {
return true;
} else if (StringUtils.countMatches(tok, 'd') == 1
&& !tok.equalsIgnoreCase("d")) {
return true;
} else {
try {
Integer.parseInt(tok);
return true;
} catch (NumberFormatException nfx) {
return false;
}
}
}
/**
* Check if a token represents an operator
*
* @param tok
* The token to check if it represents an operator
* @return Whether or not the token represents an operator
*/
private boolean isOperator(String tok) {
switch (tok) {
case ":=":
case "+":
case "-":
case "*":
case "/":
case "c":
case "d":
return true;
default:
return false;
}
}
}
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