Traditional Functions and Operators

Traditional Functions and Operators are the original user-defined functions and operators that are part of the APL standard. They are referred to herein as Traditional or TradFns to distinguish them from Dfns and Dops which are unique to Dyalog.

TradFns may be defined and edited using the Dyalog Editor or may be instantiated from an array containing source code using the system function ⎕FX. The converse system functions ⎕CR, ⎕VR, ⎕NR return the original source code.

A defined function or operators is composed of lines. The first line (line 0) is called the header. Remaining lines are APL statements, called the body.

The header consists of the following parts:

  1. its model syntactical form,
  2. an optional list of local names, each preceded by a semi-colon (;) character,
  3. an optional comment, preceded by the symbol ⍝.

Only the model is required. If local names and comments are included, they must appear in the prescribed order.