Change/add symbol for omitted default arguments?

[Judd Storrs]

Octave allows default values for function arguments such as

function [a,b,c] = myfunc(d,e=3,f)

    ....

endfunction

When calling the function the default parameter can be used by entering the ":" symbol.

[a,b,c] = myfunc(3,:,5)

http://www.network-theory.co.uk/docs/octave3/octave_104.html

Recent versions of octave (and Matlab apparently) have adopted ~ to mark ignored output parameters. Given this change I think it would be congruous for the octave language to also adopt the ~ for omitted default input arguments.

[a,~,b] = myfunc(3,~,5)

An alternative would be to allow : to also mark ignored output parameters.

[a,:,b] = myfunc(3,:,5)

"~" carries the meaning of "not" in octave and seems semantically more correct than ":" which carries the meaning "all".

--judd

[According to comments on StackOverflow Matlab additionally uses ~ inside function declarations to mark positional parameters that are ignored by the function definition. I'm not entirely sure what this achieves due to the copy-on-write parameter passing except that perhaps Matlab may be able to skip evaluating the arguments. I don't think that particular optimization can play nice with octave's evaluation model which allows things like myfunc(3,f=myfunc2(g=5),5) with the second parameter marked ~ in the function definition]