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Issue 517 - add some interim error checking and reporting

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git-svn-id: http://google-refine.googlecode.com/svn/trunk@2420 7d457c2a-affb-35e4-300a-418c747d4874
This commit is contained in:
Tom Morris 2012-01-12 06:20:28 +00:00
parent 8ec10a6ea6
commit fa2e6fe608
2 changed files with 14 additions and 7 deletions
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9
main/src/com/google/refine/expr/functions/math/Combin.java
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@ -59,16 +59,17 @@ public class Combin implements Function {
return Combin.combination(((Number) args[0]).intValue(), ((Number) args[1]).intValue());
}
public static int combination(int n, int k){
public static long combination(long n, long k){
if (k > n) {
throw new IllegalArgumentException ("the number of elements, n, should be larger than the number of combinations, k");
}
if (n < 1) {
throw new IllegalArgumentException ("the number of elements, n, cannot be less than 1");
}
int nFact = FactN.factorial(n, 1);
int rFact = FactN.factorial(k, 1);
int nminusrFact = FactN.factorial(n - k, 1);
// TODO: This needs to use a more efficient Binomial Coefficient algorithm
long nFact = FactN.factorial(n, 1);
long rFact = FactN.factorial(k, 1);
long nminusrFact = FactN.factorial(n - k, 1);
return nFact / (rFact * nminusrFact);
}

12
main/src/com/google/refine/expr/functions/math/FactN.java
View File

@ -65,11 +65,17 @@ public class FactN implements Function {
* e.g. A double factorial would have a step of 2.
* Returns 1 for zero and negative integers.
*/
public static int factorial(int i, int step){
if(i <= 1) {
public static long factorial(long i, long step){
if (i < 0) {
throw new IllegalArgumentException("Can't compute the factorial of a negative number");
} else if(i <= 1) {
return 1;
} else {
return i * FactN.factorial(i - step, step);
long result = i * FactN.factorial(i - step, step);
if (result < 0) {
throw new ArithmeticException("Integer overflow computing factorial");
}
return result;
}
}