Re: foo_cs = foo{:} - feature or bug ? (octave-3.4.2); also, sizeof(foo{:})

[John W. Eaton]

On  8-Aug-2011, Sergei Steshenko wrote:

| comma separated list is _not_ converted when 'sizeof' is called, but
| some _deafault_ conversion is called in case of
| 
| "
| octave:4> foo_cs = foo{:}
| foo_cs = a

The expression

  foo = {a, b, c}
  foo{:}

behaves as if you had typed

  foo = {a, b, c}
  a, b, c

In other words, a "comma-separated list" is a set of
independent expressions, not a single expression.

If you write

  foo = {a, b, c}
  x = foo{:}

This is equivalent to

  foo = {a, b, c}
  x = foo{1}, foo{2}, foo{3}

but the results of the expressions foo{2} and foo{3} are not printed.
FWIW, this behavior is compatible with Matlab, and we have this syntax
and semantics for compatibility with Matlab; we did not invent it
solely to confuse you.

| I.e. why for arithmetic expressions in case of "sizeof(1 + 2)" I see
| something like:
| 
| invisible_result = 1 + 2; sizeof(invisible_result)

Because 1+2 is an expression that produces a single value.

| but for comma-separated list in case of "sizeof(foo{:})" I do _not_ see
| 
| invisible_result = foo{:}; sizeof(invisible_result)

Because, assuming that foo in the expression above is a cell array,
the expression

  invisible_result = foo{:}

is equivalent to writing

  invisible_result = foo{1}, foo{2}, ..., foo{end}

and

  sizeof (foo{:})

is equivalent to

  sizeof (foo{1}, foo{2}, ..., foo{end})

but sizeof does not accept multiple arguments, so it is an error to
call it this way.

jwe