# Set prolog flag: prefer\_rationals
**URL:** https://swi-prolog.discourse.group/t/set-prolog-flag-prefer-rationals/6582
**Category:** General
**Created:** [May 27, 2023, 7:29pm UTC](https://swi-prolog.discourse.group/t/set-prolog-flag-prefer-rationals/6582 "2023-05-27T19:29:50Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@ppadilcdx](https://swi-prolog.discourse.group/u/ppadilcdx)
#### Post date: [May 27, 2023, 7:29pm UTC](https://swi-prolog.discourse.group/t/set-prolog-flag-prefer-rationals/6582/1 "2023-05-27T19:29:50Z")
Pardon if this is a duplicate - I’m new to swipl forums. I set the prefer\_rationals to true, the manual says that integer division (//) should produce a rational number but I’m getting 0 from `X is 3//7.`. Am I missing something? Thanks.
PS. Apologies if duplicate topic. I did search but didn’t find anything appropriate.
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### Author:  [@ppadilcdx](https://swi-prolog.discourse.group/u/ppadilcdx)
#### Post date: [May 27, 2023, 7:48pm UTC](https://swi-prolog.discourse.group/t/set-prolog-flag-prefer-rationals/6582/2 "2023-05-27T19:48:08Z")
My bad. Misread the manual. Please ignore…