41 lines
1.2 KiB
Java
41 lines
1.2 KiB
Java
package function.builtin;
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import function.*;
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import sexpression.*;
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public class MULTIPLY extends LispFunction {
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private ArgumentValidator argumentValidator;
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public MULTIPLY() {
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this.argumentValidator = new ArgumentValidator("*");
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this.argumentValidator.setEveryArgumentExpectedType(LispNumber.class);
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}
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public LispNumber call(Cons argumentList) {
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argumentValidator.validate(argumentList);
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return callTailRecursive(new Cons(LispNumber.ONE, argumentList));
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}
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private LispNumber callTailRecursive(Cons argumentList) {
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Cons remainingArguments = (Cons) argumentList.getCdr();
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SExpression firstArgument = argumentList.getCar();
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LispNumber number1 = (LispNumber) firstArgument;
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if (remainingArguments.nullp())
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return number1;
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SExpression secondArgument = remainingArguments.getCar();
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LispNumber number2 = (LispNumber) secondArgument;
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LispNumber product = new LispNumber(number1.getValue().multiply(number2.getValue()));
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SExpression remainingNumbers = remainingArguments.getCdr();
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if (!remainingNumbers.consp())
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return product;
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return callTailRecursive(new Cons(product, remainingNumbers));
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}
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}
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