One argument that is repeated, one argument in c from itertools import repeat for result in executor.map(f, repeat(a), c): pass Need to unpack items of c, and can unpack c from itertools import izip for result in executor.map(f, *izip(*c)): pass Need to unpack items of c, can’t unpack c Change f to take a single … Read more
Your iterator type is Iterator<Item = Self::Item>, but Iterator is a trait. Traits are implemented by structs, they don’t exist on their own. You could also have a reference trait object (&Iterator), a boxed trait object (Box<Iterator>) or an anonymous trait implementation (impl Iterator), all of which have a known sizes. Instead, we create a … Read more
You want to use generics here: fn find_min<‘a, I>(vals: I) -> Option<&’a u32> where I: Iterator<Item = &’a u32>, { vals.min() } Traits can be used in two ways: as bounds on type parameters and as trait objects. The book The Rust Programming Language has a chapter on traits and a chapter on trait objects … Read more
First of all, there are 2 kinds of for loops, which behave very differently. One uses indices: for (int i = 0; i < list.size(); i++) { Thing t = list.get(i); … } This kind of loop isn’t always possible. For example, Lists have indices, but Sets don’t, because they’re unordered collections. The other one, … Read more
You can use the Iterator::enumerate method: fn main() { let v = vec![1; 10]; for (pos, e) in v.iter().enumerate() { println!(“Element at position {}: {:?}”, pos, e); } } Playground
Am I doing that right, as far as iterating through the Arraylist goes? No: by calling iterator twice in each iteration, you’re getting new iterators all the time. The easiest way to write this loop is using the for-each construct: for (String s : arrayList) if (s.equals(value)) // … As for java.lang.ArrayIndexOutOfBoundsException: -1 You just … Read more
Just do a simple .keys() >>> dct = { … “1”: “a”, … “3”: “b”, … “8”: { … “12”: “c”, … “25”: “d” … } … } >>> >>> dct.keys() [‘1’, ‘8’, ‘3’] >>> for key in dct.keys(): print key … 1 8 3 >>> If you need a sorted list: keylist = dct.keys() … Read more
What is the difference between them … “Fail-safe” (in engineering) means that something fails in a way that causes no or minimal damage. Strictly speaking, there is no such thing in Java as a fail-safe iterator. If an iterator fails (in the normal sense of “fail”), you can expect damage to occur. I suspect that … Read more
It’s lazy. It’s fairly easy to prove that’s the case: >>> def abc(): … letters = [‘a’,’b’,’c’] … for letter in letters: … print letter … yield letter … >>> numbered = enumerate(abc()) >>> for i, word in numbered: … print i, word … a 0 a b 1 b c 2 c
I’ll give this a try. Note that I’m not affiliated with ECMA and have no visibility into their decision-making process, so I cannot definitively say why they have or have not done anything. However, I’ll state my assumptions and take my best shot. 1. Why add a for…of construct in the first place? JavaScript already … Read more