Re: Functions in scripts

[John W. Eaton]

On 01/24/2017 02:52 PM, Rik wrote:

> Thanks.  So Matlab is reading through the entire script once and
> accepting forward declarations.  There should be a way to accomplish the
> same thing in Octave because Octave already knows how to do this for
> function files and forward declarations of subfunctions.

Octave also reads a script file completely and creates a parse tree that 
is executed later.  A parsed script is stored as an octave_user_script 
object, which is slightly different from an octave_user_fcn object (no 
arguments or return values and different behavior when it is executed).

Within a script, Octave stores an object in the parse tree for each 
function definition.  When the script is executed, function objects are 
inserted in the symbol table as they are encountered in the parse tree. 
It should be fairly straightforward to instead make a list of all the 
function objects in the script and evaluate them first, before the rest 
of the statements in the script.

It should also be reasonably easy to make the functions local to the 
script if that is what Matlab is doing.  But that is incompatible with 
the way Octave currently works, so we'd have to make a choice about 
exactly what we want the behavior to be, whether we want to try to 
maintain backward compatibility with older versions of Octave, etc.

jwe