Mailing List Archive: 49091 messages

# Math (division)

### [1/3] from: ammoncooke::yahoo::com at: 30-May-2001 19:38

I know there is a way to tell is a number is non-decimal, I just don't know the way! ;)) Could someone please help me?? Your help is appreciated. Ammon

### [2/3] from: larry:ecotope at: 30-May-2001 19:38

Hi Ammon If you just want to know if it is a REBOL integer: integer? x If you want to know if a number has no digits after the decimal place (i.e., it is an integer in the mathematical sense), regardless of its REBOL type:
>> math-int: func [x [number!]][x // 1 = 0] >> math-int pi
== false
>> x: to-decimal 2
== 2
>> type? x
== decimal!
>> math-int x
== true
>> type? 2 ** 52
== decimal!
>> math-int 2 ** 52
== true
>> math-int -2 ** 52
== true HTH -Larry ----- Original Message ----- From: "Ammon Cooke" <[ammoncooke--yahoo--com]> To: <[rebol-list--rebol--com]> Sent: Wednesday, May 30, 2001 4:38 AM Subject: [REBOL] Math (division) I know there is a way to tell is a number is non-decimal, I just don't know the way! ;)) Could someone please help me?? Your help is appreciated. Ammon

### [3/3] from: larry:ecotope at: 30-May-2001 21:34

Hi all Actually there is a flaw in the implementation of the REBOL comparison operators (=, >=, <=, equal?, greater?, lesser?, etc.) when applied to the decimal! type. To be sure the math-int function works correctly for ALL cases, it should be changed to: math-int: func [x [number!]][ zero? x // 1] An example of the problem:
>> math-int 1e-20
== false which is correct. The function below using equal will return true which is not correct. One manifestation of the flaw is:
>> 0 = 1e-20
== true
>> positive? 1e-20 - 0
== true
>> zero? 1e-20
== false
>>
The functions zero? positive? and negative? work correctly for the decimal! type, but = gives an incorrect answer. -Larry ----- Original Message ----- From: "Larry Palmiter" <[larry--ecotope--com]> To: <[rebol-list--rebol--com]> Sent: Wednesday, May 30, 2001 7:38 PM Subject: [REBOL] Re: Math (division) Hi Ammon If you just want to know if it is a REBOL integer: integer? x If you want to know if a number has no digits after the decimal place (i.e., it is an integer in the mathematical sense), regardless of its REBOL type:
>> math-int: func [x [number!]][x // 1 = 0] >> math-int pi
== false
>> x: to-decimal 2
== 2
>> type? x
== decimal!
>> math-int x
== true
>> type? 2 ** 52
== decimal!
>> math-int 2 ** 52
== true
>> math-int -2 ** 52
== true HTH -Larry