Clarifying two situations of overflow.

QuantEcon · Jan 7, 2018 · a645c2d · a645c2d
1 parent 1e44060
commit a645c2d
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/src/util.jl b/src/util.jl
@@ -340,10 +340,10 @@ the descending sequences of the elements, following
 
 # Notes
 
-`InexactError` exception will be thrown if overflow occurs during
-the computation. It is the user's responsibility to ensure
-that the rank of the input array fits within the range of `T`;
-a sufficient condition for it is 
+`InexactError` exception will be thrown, or an incorrect value will be
+returned without warning if overflow occurs during the computation.
+It is the user's responsibility to ensure that the rank of the input
+array fits within the range of `T`; a sufficient condition for it is 
 `binomial(BigInt(a[end]), BigInt(length(a))) <= typemax(T)`.
 
 # Arguments

diff --git a/test/test_util.jl b/test/test_util.jl
@@ -113,10 +113,16 @@
 
         @test k_arrays_computed == k_arrays
 
+        # test InexactError when ranking is out of range
         n, k = 100, 50
         @test k_array_rank(BigInt, collect(n-k+1:n)) == binomial(BigInt(n), BigInt(k))
         @test_throws InexactError k_array_rank(collect(n-k+1:n))
 
+        # test returning wrong value when ranking is out of range
+        n, k = 68, 29
+        @test k_array_rank(BigInt, collect(n-k+1:n)) == binomial(BigInt(n), BigInt(k))
+        @test k_array_rank(collect(n-k+1:n)) != binomial(BigInt(n), BigInt(k))
+
     end
 
 end