[Octave-bug-tracker] [bug #37390] In matlab repmat can have empty inputs

[Richard]

Follow-up Comment #3, bug #37390 (project octave):

Incidentally, there are further differences in behaviour, for example the
following in ML:

>> repmat(1, [2,2], 3)

ans(:,:,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,3) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000

>> repmat(1, [2,2], 3, 3)
Error using repmat
Too many input arguments.
 
>> repmat(1, [2,2,2], 3)

ans(:,:,1,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,1,2) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2,2) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,1,3) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2,3) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000

>> repmat(1, [2,2,2], [3,3])

ans(:,:,1,1,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2,1,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,1,2,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000


ans(:,:,2,2,1) =

     1.0000e+000     1.0000e+000
     1.0000e+000     1.0000e+000
... lots more output

So it seems m and n need not be scalar in ML, the dimensions are in fact just
tacked onto each other. This is consistent with what was seen with empty
inputs. Therefore you could get rid of the error and just do something like:

# check second arg first so it will be one if both
# m and n are empty
if (isempty (n))
n = 1;
endif
if (isempty (m))
m = n;
n = 1;
endif

if isvector(m) && isvector(n)
idx = [m(:)',n(:)'];
else
error('M and N must be scalars or vectors')
endif


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