this post was submitted on 19 Jun 2023
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A quick tip for better variable names (programming.dev)
submitted 1 year ago* (last edited 1 year ago) by sisyphean@programming.dev to c/programming@programming.dev
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Whenever you store a value that has a unit in a variable, config option or CLI switch, include the unit in the name. So:

  • maxRequestSize => maxRequestSizeBytes
  • elapsedTime => elapsedSeconds
  • cacheSize => cacheSizeMB
  • chargingTime => chargingTimeHours
  • fileSizeLimit => fileSizeLimitGB
  • temperatureThreshold => temperatureThresholdCelsius
  • diskSpace => diskSpaceTerabytes
  • flightAltitude => flightAltitudeFeet
  • monitorRefreshRate => monitorRefreshRateHz
  • serverResponseTimeout => serverResponseTimeoutMs
  • connectionSpeed => connectionSpeedMbps

EDIT: I know it’s better to use types to represent units. Please don’t write yet another comment about it. You can find my response to that point here: https://programming.dev/comment/219329

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[–] Ullallulloo@civilloquy.com 11 points 1 year ago (2 children)

Those are just types. You shouldn't write types in the names. That's just redundant. If you need to check the type of a variable, hover over it and your IDE should tell you that temperatureThreshold is type DegreesCelsius. No need to add extra cruft.

This is especially problematic if you later refactor things. If you change units, then you have to rename every variable. If you overload variables, it doesn't make any sense.

Plus, variables shouldn't really be tied to a specific unit. If you need to display in Fahrenheit, you ideally just pass temperatureThreshold and it converts types as needed. A Temperature type that that has degreesF() and degreesC() functions is even cleaner. Units should just be private to the type's struct.

[–] sisyphean@programming.dev 13 points 1 year ago* (last edited 1 year ago) (1 children)

I absolutely agree. But:

  • sometimes you need to modify existing code and you can't add the types necessary without a giant refactoring
  • you can't express units with types in:
    • JSON/YAML object keys
    • XML tag or attribute names
    • environment variable names
    • CLI switch names
    • database column names
    • HTTP query parameters
    • programming languages without a strong type system

Obviously as a Hungarian I have a soft spot for Hungarian notation :) But in these cases I think it's warranted.

[–] abhibeckert@lemmy.world 2 points 1 year ago

Not sure what languages you commonly work with, but in good modern languages you can simply declare "feet" as an alias of integer (or double?), and no refactoring would be required.

And any good toolchain to parse / generate JSON/etc can absolutely get the types right.

[–] JackbyDev@programming.dev 1 points 1 year ago

There are plenty of times where the type is just something generic like an integer and making a wrapper type is not worth the effort and this is a useful approach.

[–] vtr@programming.dev 6 points 1 year ago (1 children)

That seems akin to commenting. The problem with this approach is that text is not code. It's very easy to forget to change text. In that case it becomes the worst of both worlds, you have a variable name that actually misleads you.

Much safer than this is to encode this kind of information into the code itself in such a way the program won't compile of the types are incorrect.

[–] sisyphean@programming.dev 5 points 1 year ago

I understand what you mean, and I even agree with it, but just to be a little pedantic, variable names are code, or at least they are more code than comments or docs.

But yes, encoding units into the type system is a much better solution. It doesn't work however for config options, environment variables or CLI switches.

[–] thekernel@kbin.social 6 points 1 year ago

fileSizeLimitGB

Surely its fileSizeLimitGiB

/s

[–] cgtjsiwy@programming.dev 5 points 1 year ago (2 children)

In languages with static and convenient type systems, I try to instead encode units as types. With clever C++ templating, you can even get implicit conversions (e.g. second -> hour) and compound types (e.g. meter and second types also generate m/s, m/s^2 and so on).

[–] sisyphean@programming.dev 3 points 1 year ago

IIRC F# even has built-in support for units.

[–] CoderKat@kbin.social 1 points 1 year ago

A good example is Go's time package. You'd normally express durations like 5 * time.Second and the result is a time.Duration. Under the hood, it's just an int64 nanoseconds, but you'd never use it as a plain nanoseconds. You'd instead use it like d.Seconds() to get whichever unit you desire.

[–] lavafroth@programming.dev 4 points 1 year ago

I think some of the modern languages handle this pretty well. Rust has algebraic data types thanks to its brilliant use of enums. Go has a similar type system. Taking the elapsedTime example from the post, for solving this duration related problem, a Rust programmer would use Duration::from_millis(millis) or Duration::from_secs(secs) and forget about the unit. It's a duration, that's what you wanna care about.

[–] PopGreene@programming.dev 3 points 1 year ago (1 children)

Looks like Hungarian Notation

[–] sisyphean@programming.dev 8 points 1 year ago* (last edited 1 year ago)

Related: Making Wrong Code Look Wrong

TL;DR: there is good and bad Hungarian notation. Encoding types (like string or int) in variable names is bad. Encoding information that cannot be expressed in the type system is good. (Though with the development of type systems, more and more of those concepts can be moved into the types, keeping variable names clean.)

But as a Hungarian, I'm obviously a little biased :)

[–] kresten@feddit.dk 2 points 1 year ago (1 children)

It's so annoying when you have to figure out what unit a variable is describing :(

[–] sisyphean@programming.dev 1 points 1 year ago

That constant frustration is what made me write this post :)

[–] tim@lemmy.timwaterhouse.com 2 points 1 year ago

The better fix is to try to use types that represent those units or data types (e.g. duration instead of ms). Makes it harder to accidentally use the wrong units and documents the code / intent better.

[–] mirisbowring@lemmy.primboard.de 2 points 1 year ago (2 children)

But what if the FileSize can be „1G“, „1024M“, 518K“, etc.?

Documentation itself is much more important and modern IDEs and Editors will show you what to type in :)

[–] sisyphean@programming.dev 4 points 1 year ago

In that case I would call the variable fileSizeWithUnit and also document what the possible units are. I wouldn't say that documentation is categorically more important than good naming. Both are different aspects of good software development.

[–] starman@programming.dev 2 points 1 year ago

Then use bytes

[–] state_electrician@discuss.tchncs.de 1 points 1 year ago

Variables, meh. As long as the code is clear, I don't mind too much about naming. For config options? Absolutely.

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