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Implement two combinatorics operators.

This commit is contained in:
Danila Fedorin 2017-08-09 12:34:02 -07:00
parent d6f4838f05
commit 4e042bd0eb
1 changed files with 44 additions and 0 deletions
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44
src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
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@ -136,6 +136,47 @@ public class StandardPlugin extends Plugin {
}*/
}
});
/**
* The permutation operator.
*/
public static final Operator OP_NPR = new Operator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0, new Function() {
@Override
protected boolean matchesParams(NumberInterface[] params) {
return params.length == 2 && params[0].fractionalPart().signum() == 0
&& params[1].fractionalPart().signum() == 0;
}
@Override
protected NumberInterface applyInternal(NumberInterface[] params) {
if(params[0].compareTo(params[1]) < 0 ||
params[0].signum() < 0 ||
(params[0].signum() == 0 && params[1].signum() != 0)) return fromInt(params[0].getClass(), 0);
NumberInterface total = fromInt(params[0].getClass(), 1);
NumberInterface multiplyBy = params[0];
NumberInterface remainingMultiplications = params[1];
while(remainingMultiplications.signum() > 0){
total = total.multiply(multiplyBy);
remainingMultiplications = remainingMultiplications.subtract(fromInt(params[0].getClass(), 1));
multiplyBy = multiplyBy.subtract(fromInt(params[0].getClass(), 1));
}
return total;
}
});
/**
* The combination operator.
*/
public static final Operator OP_NCR = new Operator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0, new Function() {
@Override
protected boolean matchesParams(NumberInterface[] params) {
return params.length == 2 && params[0].fractionalPart().signum() == 0
&& params[1].fractionalPart().signum() == 0;
}
@Override
protected NumberInterface applyInternal(NumberInterface[] params) {
return OP_NPR.getFunction().apply(params).divide(OP_FACTORIAL.getFunction().apply(params[1]));
}
});
/**
* The absolute value function, abs(-3) = 3
*/
@ -575,6 +616,9 @@ public class StandardPlugin extends Plugin {
registerOperator("^", OP_CARET);
registerOperator("!", OP_FACTORIAL);
registerOperator("npr", OP_NPR);
registerOperator("ncr", OP_NCR);
registerFunction("abs", FUNCTION_ABS);
registerFunction("exp", FUNCTION_EXP);
registerFunction("ln", FUNCTION_LN);