# Binary (or String) interpolation **URL:** \ **Category:** Questions / Help\ **Tags:** binary\ **Created:** [October 10, 2023, 7:20am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940 "2023-10-10T07:20:21Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 10, 2023, 7:20am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/1 "2023-10-10T07:20:21Z")
Hi all, I would like to interpolate a string or a binary. I’d like to get: `"Some Foo text"` or `<<"Some Foo text">>` Given `X = "Foo"` or `X = <<"Foo">>` This snippet is working: ```erlang X = "Foo", Result = lists:flatten(io_lib:format("Some ~s text", [X])), ``` I am wondering if there are more concise way to achieve the same result. I read about the bit syntax, but can’t make it work. This is what I tried (which is not working): ```erlang X = <<"Foo">>, Title = <<"Some ",X/utf8," text">>, ``` Thanks a lot Cheers! ---
**Author:** ![TD5](https://erlangforums.com/user_avatar/erlangforums.com/td5/32/1590_2.png) [@TD5](https://erlangforums.com/u/TD5)\ **Post date:** [October 10, 2023, 8:49am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/2 "2023-10-10T08:49:08Z")
Try: ```erlang X = <<"Foo"/utf8>>, Title = <<"Some ",X/binary," text">>, ``` In the future, [there may be more convenient ways to do a similar thing](https://github.com/erlang/otp/pull/7343). ---
**Author:** ![dgud](https://erlangforums.com/user_avatar/erlangforums.com/dgud/32/191_2.png) [@dgud](https://erlangforums.com/u/dgud)\ **Post date:** [October 10, 2023, 9:09am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/3 "2023-10-10T09:09:53Z")
Though it might be cheaper to keep them as iolists, ["Some “, X, " text”] or [\<\<“Some “\>\>, X, \<\<” text”\>\>] Most io functions take iolists as input, so the lists:flatten/1 can/should be avoided. ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 10, 2023, 9:18am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/4 "2023-10-10T09:18:58Z")
In this context the formatting with placeholders is preferred, as the word order may change in different languages. I tried removing the `flatten` and it is indeed working the same 🙂 I tried searching for `iolist` in the documentation but I cannot find any useful info, can someone point me where `iolist` is documented? Thank you ---
**Author:** ![dgud](https://erlangforums.com/user_avatar/erlangforums.com/dgud/32/191_2.png) [@dgud](https://erlangforums.com/u/dgud)\ **Post date:** [October 10, 2023, 9:36am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/5 "2023-10-10T09:36:21Z")
See the iodata and iolists in table 7.1 [https://www.erlang.org/doc/reference\_manual/typespec#types-and-their-syntax](https://www.erlang.org/doc/reference_manual/typespec#types-and-their-syntax) Even better is to look at [Unicode chardata or charlist](https://www.erlang.org/doc/man/unicode#type-chardata) ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 10, 2023, 9:39am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/6 "2023-10-10T09:39:11Z")
Thank you, will do. ---
**Author:** ![eproxus](https://erlangforums.com/user_avatar/erlangforums.com/eproxus/32/452_2.png) [@eproxus](https://erlangforums.com/u/eproxus)\ **Post date:** [October 11, 2023, 1:27pm UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/7 "2023-10-11T13:27:46Z")
> [@carlotm](#): > > In this context the formatting with placeholders is preferred, as the word order may change in different languages. I/O lists are the preferred way to concatenate data like this in Erlang. You can easily do dynamic stuff, e.g. `["foo", dynamic(Input), "bar"]` which will get rendered properly and efficiently when it leaves the system through a socket, file, standard out etc. ---
**Author:** ![fancycade](https://erlangforums.com/user_avatar/erlangforums.com/fancycade/32/1187_2.png) [@fancycade](https://erlangforums.com/u/fancycade)\ **Post date:** [October 12, 2023, 3:50am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/8 "2023-10-12T03:50:57Z")
This is the real answer. Nice way to take advantage of iolist behavior. ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 12, 2023, 4:51am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/9 "2023-10-12T04:51:44Z")
> [@eproxus](#): > > I/O lists are the preferred way to concatenate data like this in Erlang. You can easily do dynamic stuff, e.g. `["foo", dynamic(Input), "bar"]` which will get rendered properly and efficiently when it leaves the system through a socket, file, standard out etc. Ok. I suppose I will ignore translations for now. I know they will come though, (will search for a gettext library that day, and hopefully one that supports interpolation) Cheers! ---
**Author:** ![eproxus](https://erlangforums.com/user_avatar/erlangforums.com/eproxus/32/452_2.png) [@eproxus](https://erlangforums.com/u/eproxus)\ **Post date:** [October 12, 2023, 7:33am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/10 "2023-10-12T07:33:41Z")
> [@carlotm](#): > > I suppose I will ignore translations for now. If you use IO lists you get both performance and dynamic content, such as translations. Example: ```erlang [?TXT2("Hello", LangCode), $\s, UserName, $!] ``` Which would generate for e.g. Swedish `["Hej", $\s, "Carlo", $!]` which when outputted would be concatenated by the Erlang VM to `"Hej Carlo!"`. ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 12, 2023, 7:45am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/11 "2023-10-12T07:45:37Z")
> [@eproxus](#): > > If you use IO lists you get both performance and dynamic content But I am stuck with the order of the list. In many cases the order of the dynamic and static content changes based on the language. Example: English → `The user "UUU" has finished the task "TTT".` Deutsch → `Der Benutzer "UUU" hat die Aufgabe "TTT" abgeschlossen.` Where `UUU` and `TTT` are the dynamic parts. Or am I missing something here? Cheers! ---
**Author:** ![eproxus](https://erlangforums.com/user_avatar/erlangforums.com/eproxus/32/452_2.png) [@eproxus](https://erlangforums.com/u/eproxus)\ **Post date:** [October 12, 2023, 8:11am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/12 "2023-10-12T08:11:40Z")
I haven’t used gettext at all, but I would think a good translation libraries should have some templating functionality. English → `The user "${USER}" has finished the task "${TASK}"` Deutsch → `Der Benutzer "${USER}" hat die Aufgabe "${TASK}" abgeschlossen.` ```erlang ``` ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 12, 2023, 8:14am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/13 "2023-10-12T08:14:23Z")
Yeah yeah, pretty sure as well. This one looks sick: > **[GitHub - ergenius/t\_\_: Erlang gettext](https://github.com/ergenius/t__#singular-terms-with-interpolation)** > > Erlang gettext. Contribute to ergenius/t\_\_ development by creating an account on GitHub. I’ll stick with iolists for now and see when I’ll need some more advanced stuff Cheers! ---
**Author:** ![williamthome](https://erlangforums.com/user_avatar/erlangforums.com/williamthome/32/471_2.png) [@williamthome](https://erlangforums.com/u/williamthome)\ **Post date:** [October 12, 2023, 12:08pm UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/14 "2023-10-12T12:08:54Z")
FWIW, I created just for fun a lib that does string interpolation: > **[GitHub - williamthome/interpolate: An Erlang library to interpolate strings.](https://github.com/williamthome/interpolate)** > > An Erlang library to interpolate strings. Contribute to williamthome/interpolate development by creating an account on GitHub. > **[Erlang Interpolate - Visual Studio Marketplace](https://marketplace.visualstudio.com/items?itemName=williamthome.erlang-interpolate)** > > Extension for Visual Studio Code - Syntax highlighter to the Erlang Interpolate lib. BTW, I recommend the use of [IO lists](https://github.com/gar1t/erlang-patterns/blob/master/patterns/iolist.md). ---
**Author:** ![eproxus](https://erlangforums.com/user_avatar/erlangforums.com/eproxus/32/452_2.png) [@eproxus](https://erlangforums.com/u/eproxus)\ **Post date:** [October 12, 2023, 12:52pm UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/15 "2023-10-12T12:52:25Z")
> [@williamthome](#): > > BTW, I recommend the use of [IO lists](https://github.com/gar1t/erlang-patterns/blob/master/patterns/iolist.md). Yeah, it is often I see superfluous `iolist_to_binary/1` or `lists:flatten/1` calls when they are not necessary in Erlang. It’s a common beginner anti-pattern. ---
**Author:** ![nzok](https://erlangforums.com/letter_avatar_proxy/v4/letter/n/4af34b/32.png) [@nzok](https://erlangforums.com/u/nzok)\ **Post date:** [October 13, 2023, 4:44am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/16 "2023-10-13T04:44:33Z")
Is the word order the only thing that may change with language? I used to teach students about internationalisation, and there’s a long long list of things. - Dates and times are a big one. It’s not just that months and days have different names in different languages, the whole structure of the calendar may be different. What if your customer wants dates displayed on the Hindu traditional calendar? (In this country there are the Gregorian calendar with English words, the Gregorian calendar with Maori words, and N versions of “the” traditional Maori calendar, with different ideas about when to start a new year. You are NOT going to be able to format dates on any of the traditional calendars with C’s strftime() or its analogues in other languages.) - Numbers. Different rules for which characters are grouping characters and where they go. And of course there are different digits. Unicode 13 had 64 honest-to-goodness sets of digits, not counting 21 oddballs. - Currency. It’s not just formatting, it’s conversion. I have free account with [OpenExchangeRates.com](http://OpenExchangeRates.com), but that limits how often I can access it. Speaking of formatting, there is a fundamental problem with relying on C’s locale support. If you want guidance for how to display Yuan in Australia, you’re out of luck. The C locale model says “if you’re in Australia you only deal with Australian dollars, so XXXX you.” This really is not the kind of stuff that you can reasonably encode in a string. - Weights and measures. Obvious. But there are formatting differences as well as differences in what the units are. - Place names. The same place may have different names even in the same country (Wellington vs Pōneke, for example). We really need a decent multilingual gazeteer. ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 13, 2023, 6:30am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/17 "2023-10-13T06:30:31Z")
Yeah. Indeed making an application truly “international” involves much more than just translate messages. BTW in Elixir I am using this library [GitHub - elixir-cldr/cldr: Elixir implementation of CLDR/ICU](https://github.com/elixir-cldr/cldr) which does a very good job. ---
**Author:** ![carlotm](https://erlangforums.com/user_avatar/erlangforums.com/carlotm/32/1870_2.png) [@carlotm](https://erlangforums.com/u/carlotm)\ **Post date:** [October 13, 2023, 6:30am UTC](https://erlangforums.com/t/binary-or-string-interpolation/2940/18 "2023-10-13T06:30:53Z")
Nice one! Thanks