Erm, no? You write f(w: Walrus) -> Walrus and then let the caller handle Walrus|None and Iterable[Walrus] however they wish!
And if someone decides the codebase needs an abstraction over (and therefore specific functions to handle) Iterable[Walrus|None] then you check the weather and suggest they take a break and go for a stroll. (You check the weather to see if you should lend them your brolly.)
Honestly, this just looks like one of those lingo-heavy-but-surface-level blog posts that used to make functional programming spaces so insufferable to everyone on the outside
These things are so divorced from the reality of programming, even when they involve actual code instead of fancy lingo. Like in Scala, not a pure functional language, tutorials used to find the most convoluted higher-order functional way to do simple things.
Can't speak for C# but in C/C++ the optimization can rarely be applied safely due to aliasing. If any part of the data you're working with involves a char* then C/C++ optimizers refrain from doing these kinds of optimizations because of how difficult it is to guarantee the absence of mutability.
At least in JVM land, it's pretty easy to thwart that optimization. Particularly if the condition is on a mutable yet unchanged in the loop value.
For example:
var map = new HashMap<String, String>();
map.put("foo", "bar");
for (var i : items) {
if ("bar".equals(map.get("foo")) {
doStuff(i);
}
}
Even though `map` isn't mutated, it's hard enough for the JVM to detect and the underlying `get` functions are complex enough that it'll run the `get("foo")` every time, which can be quiet expensive.
Didn’t see it mentioned in the article but isn’t leading with if-statement called a “guard clause”.
I like that pattern but it’s just general best practice I thought.
They're one of those good practices that look like bad practice to everyone who just got a CS degree. Seems ex-students are unsettled by asymmetry or want to minimize the number of return statements.
I think it's sort of obvious that the limit to this general rule is when data dependencies between fors and ifs forbid you from pushing things further up/down.
"the loop runs without a branch, and is a candidate for vectorization".
That's it, that's the article. This matters a lot in huge-scale / scientific computing / HPF, where if you can express something as an operation on vectors on matrices, you win big (those ops parallelize well, can be run on GPUs, clusters, what have you).
And if someone decides the codebase needs an abstraction over (and therefore specific functions to handle) Iterable[Walrus|None] then you check the weather and suggest they take a break and go for a stroll. (You check the weather to see if you should lend them your brolly.)
What am I missing?
Speed was almost never the reason.
Of note, as of C#9 (and maybe prior), the dotnet runtime does this automatically whenever it is deemed safe. https://devblogs.microsoft.com/dotnet/performance-improvemen...
The same technique is applied as an optimization, when deemed safe, in all current gen c compilers (gcc, llvm, etc).
I'm very confused why neither measurements nor references to when this is done automatically in most modern languages is included in the article.
For example:
Even though `map` isn't mutated, it's hard enough for the JVM to detect and the underlying `get` functions are complex enough that it'll run the `get("foo")` every time, which can be quiet expensive.They're one of those good practices that look like bad practice to everyone who just got a CS degree. Seems ex-students are unsettled by asymmetry or want to minimize the number of return statements.
https://docs.swift.org/latest/documentation/the-swift-progra...
https://github.com/taolson/Admiran/blob/main/examples/fizzBu...
/s
"the loop runs without a branch, and is a candidate for vectorization".
That's it, that's the article. This matters a lot in huge-scale / scientific computing / HPF, where if you can express something as an operation on vectors on matrices, you win big (those ops parallelize well, can be run on GPUs, clusters, what have you).