Link

, or  in J, is a dyadic primitive function which builds a nested vector out of the two arguments. Link is useful for building a nested array when stranding by juxtaposition is not available. Link first appeared as an extension to SHARP APL.

Examples
Link implements  or , that is, the concatenation of enclose of the left argument and nest (enclose if simple) of the right argument. This allows to chain the function over multiple arrays to form a nested array. Note that both SHARP APL and J use flat array model, so they allow boxing of a simple scalar.

Because of the function's asymmetric nature, oddities may appear if the arrays are chained in a wrong order:

Similarly, the chaining fails if the rightmost array is already nested:

What we really wanted was:

Link is different from Pair, as Pair simply encloses both arguments and always produces a length-2 vector, so it cannot be used to construct a long nested array of uniform depth like Link does.

Documentation

 * J Dictionary, NuVoc