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## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
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########################################################################

## -*- texinfo -*-
## @deftypefn {} {} mustBeInteger (@var{x})
##
## Requires that input @var{x} is integer-valued (but not necessarily
## integer-typed).
##
## Raises an error if any element of the input @var{x} is not a finite,
## real, integer-valued numeric value, as determined by various checks.
##
## @end deftypefn

function mustBeInteger (x)
  if isinteger (x) || islogical (x)
    return
  endif
  but = [];
  if ! isnumeric (x)
    but = sprintf ("it was non-numeric (got a %s)", class (x));
  elseif any (! isfinite (x))
    but = "there were Inf values";
  elseif ! isreal (x)
    but = "it was complex";
  elseif ! all (floor (x) == x)
    but = "it had fractional values in some elements";
  end
  if ! isempty (but)
    label = inputname (1);
    if isempty (label)
      label = "input";
    endif
    error ("%s must be integer-valued; but %s", label, but);
  endif
endfunction

%!test
%! mustBeInteger ([])
%! mustBeInteger (42)
%! mustBeInteger (1:1000)
%! mustBeInteger (int32(42))

%!error mustBeInteger ()
%!error mustBeInteger (1.23)
%!error mustBeInteger ([1 2 3 4.4])
%!error mustBeInteger (Inf)
%!error mustBeInteger (NaN)
