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PlantUML is a component that allows to quickly write diagrams from text.
// THIS FILE HAS BEEN GENERATED BY A PREPROCESSOR.
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package net.sourceforge.plantuml.tim.expression;
import java.util.ArrayDeque;
import java.util.Deque;
import net.sourceforge.plantuml.tim.EaterException;
import net.sourceforge.plantuml.tim.EaterExceptionLocated;
// https://en.wikipedia.org/wiki/Shunting-yard_algorithm
// https://en.cppreference.com/w/c/language/operator_precedence
public class ShuntingYard {
final private TokenStack ouputQueue = new TokenStack();
final private Deque operatorStack = new ArrayDeque<>();
private static final boolean TRACE = false;
private void traceMe() {
if (TRACE == false)
return;
System.err.println("-------------------");
System.err.println("operatorStack=" + operatorStack);
System.err.println("ouputQueue=" + ouputQueue);
System.err.println("");
}
public ShuntingYard(TokenIterator it, Knowledge knowledge) throws EaterException, EaterExceptionLocated {
while (it.hasMoreTokens()) {
final Token token = it.nextToken();
traceMe();
if (TRACE)
System.err.println("token=" + token);
if (token.getTokenType() == TokenType.NUMBER || token.getTokenType() == TokenType.QUOTED_STRING) {
ouputQueue.add(token);
} else if (token.getTokenType() == TokenType.FUNCTION_NAME) {
operatorStack.addFirst(token);
} else if (token.getTokenType() == TokenType.PLAIN_TEXT) {
final String name = token.getSurface();
final TValue variable = knowledge.getVariable(name);
if (variable == null) {
if (isVariableName(name) == false)
throw EaterException.unlocated("Parsing syntax error about " + name);
ouputQueue.add(new Token(name, TokenType.QUOTED_STRING, null));
} else {
ouputQueue.add(variable.toToken());
}
} else if (token.getTokenType() == TokenType.OPERATOR) {
while ((thereIsAFunctionAtTheTopOfTheOperatorStack() //
|| thereIsAnOperatorAtTheTopOfTheOperatorStackWithGreaterPrecedence(token) //
|| theOperatorAtTheTopOfTheOperatorStackHasEqualPrecedenceAndIsLeftAssociative(token)) //
&& theOperatorAtTheTopOfTheOperatorStackIsNotALeftParenthesis(token))
ouputQueue.add(operatorStack.removeFirst());
// push it onto the operator stack.
operatorStack.addFirst(token);
} else if (token.getTokenType() == TokenType.OPEN_PAREN_FUNC) {
operatorStack.addFirst(token);
} else if (token.getTokenType() == TokenType.OPEN_PAREN_MATH) {
operatorStack.addFirst(token);
} else if (token.getTokenType() == TokenType.CLOSE_PAREN_FUNC) {
while (operatorStack.peekFirst() != null
&& operatorStack.peekFirst().getTokenType() != TokenType.OPEN_PAREN_FUNC)
ouputQueue.add(operatorStack.removeFirst());
final Token first = operatorStack.removeFirst();
ouputQueue.add(first);
} else if (token.getTokenType() == TokenType.CLOSE_PAREN_MATH) {
while (operatorStack.peekFirst().getTokenType() != TokenType.OPEN_PAREN_MATH)
ouputQueue.add(operatorStack.removeFirst());
if (operatorStack.peekFirst().getTokenType() == TokenType.OPEN_PAREN_MATH)
operatorStack.removeFirst();
} else if (token.getTokenType() == TokenType.COMMA) {
while (operatorStack.peekFirst() != null
&& operatorStack.peekFirst().getTokenType() != TokenType.OPEN_PAREN_FUNC)
ouputQueue.add(operatorStack.removeFirst());
} else {
throw new UnsupportedOperationException(token.toString());
}
}
while (operatorStack.isEmpty() == false) {
final Token token = operatorStack.removeFirst();
ouputQueue.add(token);
}
// System.err.println("ouputQueue=" + ouputQueue);
}
private boolean isVariableName(String name) {
return name.matches("[a-zA-Z0-9.$_]+");
}
private boolean thereIsAFunctionAtTheTopOfTheOperatorStack() {
final Token top = operatorStack.peekFirst();
return top != null && top.getTokenType() == TokenType.FUNCTION_NAME;
}
private boolean thereIsAnOperatorAtTheTopOfTheOperatorStackWithGreaterPrecedence(Token token) {
final Token top = operatorStack.peekFirst();
if (top != null && top.getTokenType() == TokenType.OPERATOR
&& top.getTokenOperator().getPrecedence() > token.getTokenOperator().getPrecedence())
return true;
return false;
}
private boolean theOperatorAtTheTopOfTheOperatorStackHasEqualPrecedenceAndIsLeftAssociative(Token token) {
final Token top = operatorStack.peekFirst();
if (top != null && top.getTokenType() == TokenType.OPERATOR && top.getTokenOperator().isLeftAssociativity()
&& top.getTokenOperator().getPrecedence() == token.getTokenOperator().getPrecedence())
return true;
return false;
}
private boolean theOperatorAtTheTopOfTheOperatorStackIsNotALeftParenthesis(Token token) {
final Token top = operatorStack.peekFirst();
if (top != null && top.getTokenType() == TokenType.OPEN_PAREN_MATH)
return true;
return true;
}
public TokenStack getQueue() {
return this.ouputQueue;
}
}