97 lines
4.6 KiB
Text
97 lines
4.6 KiB
Text
%% title = "operator overloading is good, but getters and setters are not"
|
|
|
|
% id = "01HPEQ01JR57B057439SY90BQ9"
|
|
- this one stems from an argument I had today, so I'll write my thoughts for future generations' enjoyment here
|
|
|
|
% id = "01HPEQ01JR4YWC9Q6VYS82J0E3"
|
|
- I'll start by prefacing that I think operator overloading is good [_iff_][def:word/iff] it's implemented in a way that a single operator has only one, well-defined meaning
|
|
|
|
% id = "01HPEQ01JRBB8Z3P0KFJSR0SJN"
|
|
- this means `+` really means _addition_ and nothing else.
|
|
|
|
% id = "01HPEQ01JRJJBP9C701B36ZR4N"
|
|
- this is practically impossible to enforce at a language level - what prevents the standard library authors from overloading `+` to mean string concatenation after all?
|
|
|
|
% id = "01HPEQ01JRY7R5QGJ2AM762PPN"
|
|
- however we can at least do our best by writing good defaults and coding standards that gently suggest what to do and what not to do
|
|
|
|
% id = "01HPEQ01JR4ZC0M68818EDVDBF"
|
|
- for example, allow users to define their own arbitrary operators that are explicitly _not_ addition, to incentivize inventing new syntax for these things
|
|
|
|
% id = "01HPEQ01JRTWHH6PVNTFBDXPVT"
|
|
- the way I'd like to do it in [my dream language][def:rokugo/repo] is by a few means
|
|
|
|
% id = "01HPEQ01JRAAK5MQCZ7CFZ75FA"
|
|
- `(+)` is defined to be a polymorphic operator which calls into a module implementing the `AddSub` interface, which means you have to implement both addition _and_ subtraction for `(+)` to work on your type
|
|
|
|
```rokugo
|
|
let AddSub = interface {
|
|
type T
|
|
fun add (a : T) (b : T) : T
|
|
fun subtract (a : T) (b : T) : T
|
|
}
|
|
|
|
fun (+) (a : let T) (b : T) : T
|
|
use AS : AddSub with { T } =
|
|
AS.add a b
|
|
```
|
|
|
|
% id = "01HPEQ01JR71RV53NNSFFDV6XN"
|
|
- note how this operator _does not_ have any effects declared on it - this means addition and subtraction must not have any side effects such as I/O
|
|
|
|
% id = "01HPEQ01JRJR3ZAY24BP8TF5HH"
|
|
+ the `(add AND subtract)` rule enforces types like strings to take a different operator, because `(-)` does not have a well-defined meaning on strings
|
|
|
|
% id = "01HPEQ01JRGCPT2PGY5HK7HK7F"
|
|
- is `"foobar" - "bar" == "foo"`?
|
|
|
|
% id = "01HPEQ01JR3CVNNACZ6EGQ7NWM"
|
|
- by extension, is `"foofoobarbar" - "bar" == "foofoobar"` or `"foofoobarbar" - "bar" == "foofoo"`?
|
|
|
|
% id = "01HPEQ01JRK25NHG72ZX5XHEEJ"
|
|
- maybe characters are subtracted from the left string one by one? such that `"foobar" - "bar" == "\x04\x0e\xfcbar"` (wtf)
|
|
|
|
% id = "01HPEQ01JR25J5BY54J6RJ0KEC"
|
|
- so now getters and setters: what's so bad about them?
|
|
|
|
% id = "01HPEQ01JRQPZJEDDXV4BJN1GP"
|
|
- the problem is that given the rule above - _one operator means one thing_ - getters and setters completely destroy your assumptions about what `=` might do
|
|
|
|
% id = "01HPEQ01JR0E8C0VJZ1D9TJRAG"
|
|
- what's that? you didn't expect `camera.angle_z = 420` to throw because 420 is out of the `[-π/2, π/2]` range? oops!
|
|
|
|
% id = "01HPEQ01JR0T4C2YC7TE9ZHXHT"
|
|
- what's that? you didn't expect `camera.angle_z` to return a different value every time you access it? oh, well!
|
|
|
|
% id = "01HPEQ01JR2KWGJVP7T4SH1SXD"
|
|
- at least when it's spelled `camera.angle_z()` it suggests that it might do something weird, like access the thread RNG.
|
|
|
|
% id = "01HPEQ01JRDNA35YPYV30CJG42"
|
|
- not to mention all the infinite recursion annoyance that sometimes happens when implementing them manually
|
|
|
|
% id = "01HPEQ01JRQFSFVPQA41MFZ91T"
|
|
- this is less of a problem in languages that feature automatic generation of getters and setters - such as Kotlin
|
|
|
|
```kotlin
|
|
var someVariable: String
|
|
get
|
|
private set
|
|
// no infinite recursion to be seen here!
|
|
```
|
|
|
|
but it's still an issue in e.g. JavaScript, where one mistake can send your call stack down the spiral:
|
|
|
|
```javascript
|
|
class Example {
|
|
#someVariable = "";
|
|
|
|
get someVariable() { return this.someVariable; } // typo!!!!
|
|
set someVariable(value) { this.someVariable = value; } // typo again!!!!!!!!!! dammit!
|
|
}
|
|
```
|
|
|
|
and the error is not caught until runtime.
|
|
|
|
% id = "01HPEQ01JRMMS1B400DP6DV5M9"
|
|
- it's easy to fix but still an annoyance whenever you write a getter/setter pair.
|
|
|