Erlang parse transform for permitting default arguments in functions

Presently the Erlang syntax doesn't allow function arguments to have default parameters. Consequently a developer needs to replicate the function definition multiple times passing constant defaults to some parameters of functions.

This parse transform addresses this shortcoming by extending the syntax of function definitions at the top level in a module to have a default expression such that for A / Default argument the Default will be used if the function is called in code without that argument.

   -export([t/2]).
  
   test(A / 10, B / 20) ->
     A + B.

   -export([t/2]).
   -export([t/0, t/1]).
  
   test()    -> test(10);
   test(A)   -> test(A, 20);
   test(A,B) -> A+B.

   test(A, B, C / 1) ->    %% This is valid
     ...
  
   test(A / 1, B, C) ->    %% This is invalid
     ...