Add pattern-matching for direct definition notation
Add pattern-matching for direct definition notation

These are basically APL's version of lambda functions. Dyalog allows the
reading of arguments through the special variables ⍺ and ⍵ (representing
left and right-hand argument lists, respectively). GNU APL also supports
these variables, as well as additional variables: χ λ ⍶ ⍹. Their support
by other APL implementations is unknown.

Sources:
  * http://progopedia.com/implementation/dyalog-apl/
  * http://www.gnu.org/software/apl/apl.html#Named-Lambdas

Alhadis/language-apl