packages - Is there a bug in AssociatePairs?

Bug introduced in 10.0 and fixed in 10.1.0

---

In Version 10, the GeneralUtilities package contain some useful functions. AssociatePairs is one of those functions included in the package and advertised to work as follows:

Needs["GeneralUtilities`"]

?AssociatePairs

Well, here is an input that matches a List of pairs:

lis = Table[{k, k^3}, {k, 2, 10}];

Now,

AssociatePairs[lis]

Gives the following error:

Well, the included PairQ function disagrees with this assertion:

AllTrue[lis, PairQ]

True

So, is this a bug? Since I can't get any list of pairs to work with this function. I'm on Windows 8.1

Answer

Using Simon Woods's Spelunk we see that the body of the function is:

Self : AssociatePairs[l_] := 
 Module[{r$}, 
  r$ = Which[! Quiet[TrueQ[MatrixQ[l, PairQ]]], Message[AssociatePairs::npairs, l];
    $FailRHS, True, HoldSequence[Associate @@ Transpose[l]]];
  ReleaseHoldSequence[r$] /; ! MatchQ[r$, $FailRHS | HoldSequence[$FailRHS]]

]

I draw your attention to:

TrueQ[MatrixQ[l, PairQ]]

Recalling the definition of MatrixQ:

This means that the function is checking that:

1. 
   
   

   l (input) is a matrix

   
   


2. 
   

   each element passes PairQ

   
   

This is apparently illogical.

One could correct this with one of many other possible checks, simplest perhaps:

MatchQ[l, {{_, _} ..}]

Or to allow for SparseArray input, as may have been the motivation for MatrixQ:

MatchQ[Dimensions[l], {_, 2}] && MatrixQ[l]