{name} ← ##.fix rep                         ⍝ Fix function/operator rep.

Fixes  the function or operator from its [rep]resentation. The name of the fixed
function is returned as a shy result.

Technical note:

[fix]  uses  a technique suggested by Maurice Jordan for re-establishing the ⎕or
of a function. It works as follows:

Taking the ⎕or of a function is fast because it doesn't do anything! A _pointer_
to  the  function  is  marked as _value_, rather than _function_ in the parser's
internal  state. This  causes a name assigned to the value to have a class of 2,
rather  than  3.  Conversely, the ⎕fx of a ⎕or is fast because the parser merely
marks the pointer as _function_.

A  D-  (or  traditionally  defined) _operator_ may be given either an array or a
function  as operand. On receipt of an operand, the operator looks at the inter-
nal  structure  of  the value  passed and allocates a name class accordingly. If
the  operator  receives the ⎕or of a function as operand, it deduces that it has
been  passed  a function and sets the class (of ⍺⍺, in the case of a d:op) to 3.
Maurice's traditionally defined operator looked like this:

        ∇ Z←(QOR APPLY)A    ⍝ Apply ⎕OR of function to A
    [1]   Z←QOR A

In  the  case  of  a derived function, [fix] passes the ⎕or as _operand_ and the
[name]  as  _argument_, to an inner operator. Notice that as ⍺⍺ is quoted in the
argument  to  ⍎  that is used to effect the assignment, a dummy, unvisited ⍺⍺ is
placed  on the following line. This is in order to force the enclosing {}s to be
an operator and so receive the ⎕or as left operand, rather than left argument.

        fix←{                   ⍝ Fix function/operator rep.
            ⍺{                  ⍝ ⎕or (operand to inner operator).
                ⍎⍵,'←⍺⍺ ···'    ⍝ name derived/primitive/system function.
                ⍺⍺              ⍝ (dummy ⍺⍺ forces class).
            }⍵                  ⍝ name for assignment.


    vec                         ⍝ vector of function reps.
│ ∇tfn │ ∇dfn │┌───┬────┐│
│      │      ││afn│ ×/ ││
│      │      │└───┴────┘│

    fix¨vec                     ⍝ fix functions.

    ⎕cr¨'afn' 'dfn' 'tfn'       ⍝ function 'source'.
│  │         │z←⎕TS│

      afn dfn tfn                   ⍝ test functions.

See also: rep

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