51 lines
1.5 KiB
Java
51 lines
1.5 KiB
Java
package frontend.ast.exp;
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import frontend.ast.Node;
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import frontend.ast.NodeStack;
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import frontend.ast.SyntaxType;
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import frontend.lexer.TokenStream;
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import frontend.lexer.TokenType;
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import frontend.ast.token.TokenNode;
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import error.Errors;
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public class RelExp extends Node {
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public RelExp(TokenStream ts) {
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super(SyntaxType.REL_EXP, ts);
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}
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public void parse(Errors errors) {
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NodeStack stack = new NodeStack();
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while (true) {
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AddExp addexp = new AddExp(this.ts);
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addexp.parse(errors);
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stack.push(addexp);
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if (isRelOp()) {
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stack.push(new TokenNode(ts)); // relop
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} else {
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break;
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}
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}
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if (stack.size() == 1) {
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this.addChild((AddExp)stack.pop());
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} else {
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RelExp temp = this;
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while(stack.size() > 1) {
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RelExp rexp = new RelExp(this.ts);
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AddExp addexp = (AddExp)stack.pop();
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TokenNode relop = (TokenNode)stack.pop();
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temp.addChild(rexp);
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temp.addChild(relop);
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temp.addChild(addexp);
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temp = rexp;
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}
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temp.addChild((AddExp)stack.pop());
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}
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}
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public boolean isRelOp() {
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TokenType t = getCurrToken().getType();
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return t == TokenType.LSS || t == TokenType.GRE
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|| t == TokenType.LEQ || t == TokenType.GEQ;
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}
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}
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