Why do libraries define their own true and false?
from crimsonpoodle@pawb.social to programming@programming.dev on 15 Jan 23:23
https://pawb.social/post/18723915
from crimsonpoodle@pawb.social to programming@programming.dev on 15 Jan 23:23
https://pawb.social/post/18723915
I’m working through the vulkan tutorial and came across GLFW_TRUE and GLFW_FALSE. I presume there’s a good reason but in looking at the docs it’s just defining 1 and 0, so I’m sorta at a loss as to why some libraries do this (especially in cpp?).
Tangentially related is having things like vk_result which is a struct that stores an enum full of integer codes.
Wouldn’t it be easier to replace these variables with raw int codes or in the case of GLFW just 1 and 0?
Coming mostly from C, and having my caps lock bound to escape for vim, the amount of all caps variables is arduous for my admittedly short fingers.
Anyway hopefully one of you knows why libraries do this thanks!
#programming
threaded - newest
This is often done for backward compatibility, as stdbool.h which provides true and false wasn’t standard before C99 and even though that’s more than 25 years ago now a lot of old habits die hard.
Ahh this makes some sense
Also, plenty of embedded systems don’t use the C standard library.
stdbool.h (along with float.h, limits.h, stdarg.h, stddef.h, stdint.h, and some other library facilities) is required to be provided even in freestanding environment so, at least as long as you use an ISO C conformant compiler, you can always include those even if you don’t have a libc implementation
Yeah in the late 90's I was coding in C++ and I'm pretty sure I had to define true and false manually.
I seem to recall using the true and false literals C++ in the late '90s … looks like they were in the C++98 standard, but it’s not clear which pre-standard compilers might have supported them.
Probably readability. Correct typing maybe too. Also better error checking.
I’m not sure I understand readability? I guess is disambiguates numeric variables if you used 1 and 0. But with true and false available that would seemingly do the same thing. You still have to know what the arguments your passing are for regardless.
Does C have a logical type these days? Never use to.
I guess in reading not until c99(see other comment); they just used integers in place of Booleans, in which case your readability statement makes more sense given the historical context
For what it is worth. I learned C in 1990. Switched largely to Python in 1998.
True is not one in C. You can always compare a value to 0 if you need false but comparing to any single value for true is wrong. Often functions will return some calculated value which would be zero for false and who cares - it isn't zero so return it for true. Thus all defines of true are suspect.
stdbool.h’s true and false are macros that expand to integers 1 and 0
C23 adds a proper bool type
Only 50 years after it’s creation.
C99 has a proper boolean (_Bool), C23 makes true and false booleans (and properly gives _Bool the name bool without the macro)
A function call of “MyFunction(parameter: GLFW_TRUE)” is more readable than “MyFunction(parameter: 1)”. Not by much, mind you, but if given the choice between these two, one is clearly better. It requires no assumptions about what the reader may or may not already know about the system.It communicates intent without any ambiguity.
Some languages define True as -1, which is NOT False…
You really didn’t need this; I would have just assumed that you were speaking the truth.
CONST False = 0, True = NOT False
NOT as in the binary operator. What’s NOT of 0 in a 32 bit space? 0xFFFFFFFF, which is -1, which is ≠ 1
Different languages, and even different programmers might interpret the concept and definition of True and False differently, so to save any ambiguity and uncertainty, defining your own critical constants in your own library helps make sure your code is robust.
So… all that is NOT False either, I presume?
they mean every bit is different
I don’t know; their comment seemed pretty much the same throughout…
I once wrote a library to replace an older one. Someone did this, and users were multiplying variables by booleans and negating them in formulas.
I just made the new library less stupid and left the users to clean up their mess when migrating.
My boss insisted, before I arrived at the company, that everything in the database be coded so that 1 = Yes and 2 = No, because that’s the way he likes to think of it. It causes us daily pain.
Now I have heard everything. What is zero? Missing value?
Zero is something you always have to watch out for and handle, because he likes to use NULL for “don’t know”. I should really have deleted the database while it was still young, before they had backups.
Something like
if (stupid_bool & 0x01)should work for those.Yeah of course we convert, but it effectively means you need this little custom conversion layer between every application and its database. It’s a pain.
I imagine this would still lead to a never ending stream of subtle logic errors.
from bossland import billysbool, billysand from geography import latlong import telephony def send_missile_alert(missiles_incoming: billysbool, is_drill: billysbool, target: latlong): if billysand(missiles_incoming, not is_drill): for phone in telephony.get_all_residents(target): phone.send_alert("Missiles are inbound to your location")Can you spot the bug?
The conventional ‘not’ would not behave differently for the two non-zero values. Insidious.
Correct! I made a number of other mistakes (edited away now due to shame), but that’s the one I made on purpose.
I mean, if you have a billysbool class anyway, you’d make its truthiness correct according to bossman’s scheme, and then the not operator would work correctly.
Does your boss frequently browse the database table records outside the API?
Oh you have no idea. There is no teaching this guy.
If that is something your boss is managing, get the fuck out of there.
Microsoft SQL Server has a bit type and you always use 0 and 1 and cast/convert them. No native bool type. It’s a hassle.
Well that would be ok, because any standard tool for interfacing with the database would transparently treat bit in the DB as bool in the code. I think many DBs call it a bit rather than a bool.
that assumes you don’t write any SQL
I’m used to ORM layers where you can write SQL queries but you’re basically converting the results to objects before you use them. These kinds of things tend to handle bits OK, and bit parameters can usually be set as booleans directly. I haven’t used SQL Server in a while though so maybe it isn’t as convenient as that.
why not just take it a step further and make true = “Yes” and false = “No”
It would probably carry less risk, but in terms of bytes used this would be even worse. And we have other problems there that I’d tell you about but it would make me too sad.
I have seen this, but with “Y”, “N” instead. That was the way the database stored it and the way the UI displayed it, but everything inbetween converted to boolean instead, because there was logic depending on those choices. It wasn’t that bad, all things considered, just a weird quirk in the system. I think there was another system that did just use those strings plain (like
WHERE foo = ‘Y’in stored procedures), but nothing I had to work with. We just mapped “Y” to true when reading the query results and were done with it.(And before anyone asks, yes, we considered any other value false. If anyone complained that their “Yes”, “y” or empty was seen as false, we told them they used it wrong. They always accepted that, though they didn’t necessarily learn from it.)
Get a better boss
I’m reminded of an old job’s database where every key was named “id_foo” instead of “foo_id”
You didn’t have user_id. You had id_user. You didn’t have project_id, you had id_project. Most of the time, anyway. It was weird and no one could remember why it was like that. (Also changes to the DB were kind of just yolo, there wasn’t like a list of migrations or anything)
It’s because the Booleans sometimes are flipped in display-server technology from the 1980s, particularly anything with X11 lineage, and C didn’t have Boolean values back then. More generally, sometimes it’s useful to have truthhood be encoded low or 0, as in common Forths or many lower-level electrical-engineering protocols. The practice died off as popular languages started to have native Boolean values; today, about three quarters of new developers learn Python or ECMAScript as their first language, and FFI bindings are designed to paper over such low-level details. You’ll also sometimes see newer C/C++ libraries depending on newer standards which add native Booleans.
As a fellow vim user with small hands, here are some tricks. The verb
gUwill uppercase letters but not underscores or hyphens, so sentences likegUiwcan be used to uppercase an entire constant. The immediate action~which switches cases can be turned into a verb by:set tildeop, after which it can be used in a similar way togU. If constants are all namespaced with a prefix followed by something unique like an underscore, then the prefix can be left out of new sections of code and added back in with a macro or a:%sreplacement.In VisualBasic “true” would be represented as -1 when converted to an int because it’s all 1’s in twos complement.
By the way, you can use
g~to get the effects of tildeop without needing to set it.Seriously helpful thanks! One of my friends working on a G15 restoration project pointed out this notation to be after you did— yet while they use 0 for truth they used 20 for false so not sure were they got the second idea. And your vim tip saved me a bunch of hand ache!
It’s for the extra helpful documentation. You see, in this fantastic example, after the author set GLFW_TRUE to 1, he explained the deep and profound meaning of the value. This exemplifies that the number 1 can also be written as a word: “One”! Some people might be able to figure this out, but the author clearly went above and beyond to make the code accessible to the open source community, encouraging contributions from anyone who’s considering improving the code. Furthermore, this follows the long held tradition of man pages - explaining the nuance of the code, in preparation for telling others to RTFM when they arrogantly ask a question.
My brain is so used to seeing political content that I read “why do liberals define their own true and false” and was already like “what kind of shit take am I going to have fun reading today”
I can give you a shit take if you want one, but I don’t have shiitake mushrooms.
I like my shit takes wrapped in beef rolls, in case you come across some more :)
That should probably be red alert wakeup call for you right?
Why?
I found the comments/answers about backwards compatibility of not defined booleans and negative true interesting and plausible.
What I first thought of was that TRUE and FALSE can be redefined, so it serves as ensurance that within the library consistent values are being used no matter what other libs and callers do with their typing and definitions.
I love the description as well. “One.” “Zero.”
I work with young people starting out in IT, so I’m used to getting screenshots, and I’m so used to screenshots made with a phone instead of just capturing the screen, that I’ve stopped complaining… But come on! At least evaluate the result of the first picture and maybe do another if it’s illegible.
Yeah that’s fair— this is my focus workstation so don’t have any messaging apps or email to send the screenshot but def could have taken a second picture.
GLFW is a C library, not a C++ one, and an old one at that, and so the reason is that a long time ago, there was no bool in C. Every library would make their own true and false bc it’s handy to have.
Nowadays, the type
_Boolhas been added to C, and C++ has built-inbool, but you can still see the legacy of no boolean in C as to use the type name “bool” as well as the key words “true” and “false” for 1 and 0, you have to include “stdbool.h,” as well as in custom types in these old GL-adjacent libraries.Because JavaScript exists
i just like namespacing my variables anyway so there’s no chance of any conflicts and so you can easily change something one place instead of everywhere