Shy Result

Dfns are usually 'pure' functions that take arguments and return explicit results. Occasionally, however, the main purpose of the function might be a side-effect such as the display of information in the session, or the updating of a file, and the value of a result, a secondary consideration. In such circumstances, you might want to make the result 'shy', so that it is discarded unless the calling context requires it. This can be achieved by assigning a dummy variable after a (true) guard:

      log←{                   ⍝ Append ⍵ to file ⍺.
          tie←⍺ ⎕fstie 0      ⍝ tie number for file,
          cno←⍵ ⎕fappend tie  ⍝ new component number,
          tie←⎕funtie tie     ⍝ untie file,        
          1:rslt←cno          ⍝ comp number, shy result.
      }