Re: [OctDev] Can we implement isinteger this way?

[William P. Y. H <wil...@ya...>]

--- Quentin Spencer <qsp...@ie...> wrote:
> 
> If we're aiming for compatibility with the Matlab functions isinteger 
> and isfloat, we should look at what they do:
>  >> isinteger(1)
> ans =
>      0
> 
>  >> isinteger(int8(1))
> ans =
>      1
> 
> So, the outputs of these functions are based not on whether the contents 
> of the array happen to be integers, which can happen with a double 
> array, but on whether they are _stored_ as integers. In addition to the 
> compatibility issue, checking all elements of an array to see if they 
> are an integer could be much slower with a large array than just 
> checking the array type. Given this, it would seem that the correct 
> implementation of isinteger would involve parsing the output of the 
> typeinfo function.
> 
> -Quentin
> 

Yeah, sorry, I don't have access to a legal copy of Matlab, so... OK, then this
should be correct, right?

isfloat.m:

function retval = isfloat(A)
## -*- texinfo -*-
## @deftypefn {Function File} {} isfloat (@var{A})
## Return 1 if @var{A} is a floating point array.  Otherwise, return 0.
## @end deftypefn
##
## @seealso{isa, isinteger, isnumeric}

if (nargin ~= 1)
  usage("isfloat (A)");
end

# Octave doesn't have a single-precision floating point data type
switch (class(A))
case "double" retval = 1;
otherwise     retval = 0;
endswitch


isinteger.m:

function retval = isinteger(A)
## -*- texinfo -*-
## @deftypefn {Function File} {} isinteger (@var{A})
## Return 1 if @var{A} is an integer array.  Otherwise, return 0.
## @end deftypefn
##
## @seealso{isa, isnumeric, isfloat}

if (nargin ~= 1)
  usage("isinteger (A)");
end

switch class(A)
case  "int8"  retval = 1;
case  "int16" retval = 1;
case  "int32" retval = 1;
case  "int64" retval = 1;
case "uint8"  retval = 1;
case "uint16" retval = 1;
case "uint32" retval = 1;
case "uint64" retval = 1;
otherwise     retval = 0;
endswitch


issorted.m:

function retval = issorted(A,r)
## -*- texinfo -*-
## @deftypefn {Function File} {} issorted (@var{A}, ["rows"])
## Return 1 if @var{A} is equal to sort(@var{A}), otherwise return 0.
## If "rows" is specified, return 1 if @var{A} is equal to sortrows(@var{A}).
## @end deftypefn
##
## @seealso{sort, sortrows}

switch nargin
case 1
  retval = isequal(A,sort(A));
case 2
  if strcmp(r,"rows")
    retval = isequal(A,sortrows(A));
  else
    usage("issorted (A, [\"rows\"])");
  endif
otherwise
  usage("issorted (A, [\"rows\"])");
endswitch


isstudent.m:

function retval = isstudent
## -*- texinfo -*-
## @deftypefn {Function File} {} isstudent
## Always returns 0, because when you accept Octave's License Agreement
## you always get all the features of Octave and not a stripped-down
## "student" version.
## @end deftypefn
##
## @seealso{ispc, isunix}

if (nargin ~= 0)
  usage("isstudent");
end

retval = 0;


P.S.: I got excited and wrote those functions too...


William Poetra Yoga Hadisoeseno


	
		
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