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

Solution:<lang j> isInt =: = <.</lang> Alternative solution (remainder after diving by 1?): <lang j> isInt=: 0 = 1&|</lang> Example:<lang j> isInt 3.14 7 0 1</lang>

Perl 6

<lang perl6>for pi, 1e5, 1+0i {

   say .narrow ~~ Int;

}</lang>

Output:

False
True
True

Python

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

   return complex(f).imag == 0 and complex(f).real.is_integer()

>>> [isint(f) for f in (1.0, 2, (3.0+0.0j), 4.1, (3+4j), (5.6+0j))] [True, True, True, False, False, False] >>> </lang>

REXX

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

• 20.06.2014 Walter Pachl
• 22.06.2014 WP add complex numbers such as 13-12j etc.
• (using 13e-12 or so is not (yet) supported)
• --------------------------------------------------------------------*/

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 '1.000-3i' Call test_integer '1.000-3.3i' Call test_integer '4j' Call test_integer '2.00000000+0j' Call test_integer '0j' Call test_integer '333' Call test_integer '-1-i' Call test_integer '1+i' Call test_integer '.00i' Call test_integer 'j' Call test_integer '0003-00.0j' Exit

test_integer: Parse Arg xx Numeric Digits 1000 Parse Value parse_number(xx) With x imag If imag<>0 Then Do

 Say left(xx,13) 'is not an integer (imaginary part is not zero)'
 Return
 End

Select

 When datatype(x)<>'NUM' Then
   Say left(xx,13) 'is not an integer (not even a number)'
 Otherwise Do
   If datatype(x,'W') Then
     Say left(xx,13) 'is an integer'
   Else
     Say left(xx,13) 'isnt an integer'
   End
 End

Return parse_number: Procedure

 Parse Upper Arg x
 x=translate(x,'I','J')
 If pos('I',x)>0 Then Do
   pi=verify(x,'+-','M')
   Select
     When pi>1 Then Do
       real=left(x,pi-1)
       imag=substr(x,pi)
       End
     When pi=0 Then Do
       real=0
       imag=x
       End
     Otherwise /*pi=1*/Do
       p2=verify(substr(x,2),'+-','M')
       If p2>0 Then Do
         real=left(x,p2)
         imag=substr(x,p2+1)
         End
       Else Do
         real=0
         imag=x
         End
       End
     End
   End
 Else Do
   real=x
   imag='0I'
   End
 pi=verify(imag,'+-','M')
 If pi=0 Then Do
   Parse Var imag imag_v 'I'
   imag_sign='+'
   End
 Else
   Parse Var imag imag_sign 2 imag_v 'I'
 If imag_v= Then
   imag_v=1
 imag=imag_sign||imag_v

 Return real imag</lang>

output

3.14          isn't an integer
1.00000       is an integer
33            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
1.000-3i      is not an integer (imaginary part is not zero)
1.000-3.3i    is not an integer (imaginary part is not zero)
4j            is not an integer (imaginary part is not zero)
2.00000000+0j is an integer
0j            is an integer
333           is an integer
-1-i          is not an integer (imaginary part is not zero)
1+i           is not an integer (imaginary part is not zero)
.00i          is an integer
j             is not an integer (imaginary part is not zero)
0003-00.0j    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