68 lines
2.3 KiB
Java
68 lines
2.3 KiB
Java
package function.builtin.predicate;
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import function.*;
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import function.builtin.cons.LIST;
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import sexpression.*;
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public class EQUAL extends LispFunction {
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private ArgumentValidator argumentValidator;
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public EQUAL() {
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this.argumentValidator = new ArgumentValidator("EQUAL");
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this.argumentValidator.setExactNumberOfArguments(2);
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}
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public SExpression call(Cons argumentList) {
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argumentValidator.validate(argumentList);
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return callRecursive(argumentList);
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}
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private SExpression callRecursive(Cons argumentList) {
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Cons cdr = (Cons) argumentList.getCdr();
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SExpression firstArgument = argumentList.getCar();
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SExpression secondArgument = cdr.getCar();
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if (!isListPair(firstArgument, secondArgument))
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return equal(firstArgument, secondArgument);
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Cons listOne = (Cons) firstArgument;
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Cons listTwo = (Cons) secondArgument;
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SExpression listOneCar = listOne.getCar();
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SExpression listTwoCar = listTwo.getCar();
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SExpression listOneCdr = listOne.getCdr();
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SExpression listTwoCdr = listTwo.getCdr();
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SExpression carEqual = callRecursive(makeArgumentList(listOneCar, listTwoCar));
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SExpression cdrEqual = callRecursive(makeArgumentList(listOneCdr, listTwoCdr));
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return logicalConjunction(carEqual, cdrEqual);
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}
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private boolean isListPair(SExpression firstArgument, SExpression secondArgument) {
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return firstArgument.consp() && secondArgument.consp();
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}
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private SExpression equal(SExpression firstArgument, SExpression secondArgument) {
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return isEqual(firstArgument, secondArgument) ? Symbol.T : Nil.getInstance();
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}
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private boolean isEqual(SExpression firstArgument, SExpression secondArgument) {
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return firstArgument.toString().equals(secondArgument.toString());
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}
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private Cons makeArgumentList(SExpression listOneCar, SExpression listTwoCar) {
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return new Cons(listOneCar, LIST.makeList(listTwoCar));
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}
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private SExpression logicalConjunction(SExpression carEqual, SExpression cdrEqual) {
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return bothAreTrue(carEqual, cdrEqual) ? Symbol.T : Nil.getInstance();
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}
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private boolean bothAreTrue(SExpression carEqual, SExpression cdrEqual) {
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return (carEqual == Symbol.T) && (cdrEqual == Symbol.T);
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}
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}
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