Test integerness

Test integerness is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Given a numeric, possibly complex value, test whether or not it is an integer.

To be clear, we're not talking about whether the number is stored with the specific data type for integers, but instead we want to test whether there exists an integer with the exact same value. In other words, we want to test for integerness in the mathematical sense, not as a data type.

J

This example is incomplete. Please ensure that it meets all task requirements and remove this message.

<lang J>(= <.) 3.14 7</lang>

Output:

0 1

Perl 6

<lang perl6>say pi.narrow ~~ Int; say 1e5.narrow ~~ Int; say (1+0i).narrow ~~ Int;</lang>

Output:

False
True
True

Python

This example is incomplete. Please ensure that it meets all task requirements and remove this message.

<lang python>>>> def isint(f):

   return int(f) == f

>>> isint(3.14) False >>> isint(3.0) True >>> </lang>

REXX

This example is incomplete. Please ensure that it meets all task requirements and remove this message.

<lang rexx>/* REXX ---------------------------------------------------------------

• 20.06.2014 Walter Pachl
• zero and negative whole numbers are integers, right?
• --------------------------------------------------------------------*/

Call test_integer 3.14 Call test_integer 1.00000 Call test_integer 33 Call test_integer 999999999 Call test_integer 99999999999 Call test_integer 1e272 Call test_integer 'AA' Call test_integer '0' Call test_integer '-3' Exit test_integer: Parse Arg x Numeric Digits 1000 Select

 When datatype(x)<>'NUM' Then
   Say x 'is not an integer (not even a number)'
 /***********************************************
 When x=0 Then
   Say x 'is zero and thus not an integer'
 When x<0 Then
   Say x 'is negative and thus not an integer'
 ***********************************************/
 Otherwise Do
   If datatype(x,'W') Then
     Say x 'is an integer'
   Else
     Say x 'isnt an integer'
   End
 End

Return </lang> output

3.14 isn't an integer
33 is an integer
1.00000 is an integer
999999999 is an integer
99999999999 is an integer
1E272 is an integer
AA is not an integer (not even a number)
0 is an integer
-3 is an integer

Tcl

This example is incomplete. Please ensure that it meets all task requirements and remove this message.

The simplest method of doing this is testing whether the value is equal to the value after casting it to a integral value. <lang tcl>proc isNumberIntegral {x} {

   expr {$x == entier($x)}

} foreach x {3.14 7 1000000000000000000000} {

   puts [format "%s: %s" $x [expr {[isNumberIntegral $x] ? "yes" : "no"}]]

}</lang>

Output:

3.14: no
7: yes
1000000000000000000000: yes