# Write IEEE 754 floats in binary stream

**URL:** <https://swi-prolog.discourse.group/t/write-ieee-754-floats-in-binary-stream/7024>\
**Category:** Help!\
**Created:** [December 2, 2023, 8:40pm UTC](https://swi-prolog.discourse.group/t/write-ieee-754-floats-in-binary-stream/7024 "2023-12-02T20:40:11Z")\
**Posts on this page:** 1\
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**Author:** ![kuniaki.mukai](https://avatars.discourse-cdn.com/v4/letter/k/c67d28/32.png) [@kuniaki.mukai](https://swi-prolog.discourse.group/u/kuniaki.mukai)\
**Post date:** [December 5, 2023, 6:13am UTC](https://swi-prolog.discourse.group/t/write-ieee-754-floats-in-binary-stream/7024/6 "2023-12-05T06:13:52Z")

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> [@CapelliC](#):
>
> ```prolog
> :- use_module(library(macros)).
> 
> #define(filename, 'binserialize.bin').
> 
> ```

What is `#define` ? I tested the same lines on the latest SWIPL, but it just said “ERROR: Unknown procedure: (#)/1 (DWIM could not correct goal)”. Could you point where to read this new feature ?

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