I have a 2D list of structs that must be sequentially passed into a series of loops. Each loop will change the function in a way that affects the output from the following loop. All elements must have completed the first loop before the second loop can be started.
Currently, I have a system that looks like this:
self.list.iter().flatten().for_each(|e| { e.funcOne() });
self.list.iter().flatten().for_each(|e| { e.funcTwo() });
.....
While this does work, it is not elegant - it also requires the 2d list to be repeatedly flattened. One solution could be to store the self.list.iter().flatten() into its own variable, however, this would require the cloning of said variable each time I wanted to loop through it.
My Ideal solution would include something syntactically similar to this:
self.list.iter().flatten().for_each(|e| e.funcOne()).for_each(|e| e.funcTwo()) ....... ;
Performance-wise flattening is fine as #Chayim Friedman mentioned.
If you take a look at the flatten() source, it is not really converting the 2D-array into 1D-array. What it does is it lazily iterates over one row via a row iterator, and when the row exhausts, it switches to iterate over the next row iterator, and so on until there's no next row.
If you want a functional (one line) solution, consider this:
let functions = [
ElemType::funcOne,
ElemType::funcTwo,
];
functions.iter().for_each(|f| self.list.iter().flatten().for_each(f));
Related
Possibly very stupid question I cannot seem to find an answer for (I am beginning with code)
I want to create a simple loop which appends myArray with three objects, which are members of a custom class MyClass. The objects have the following names: "object1", "object2", "object3".
When I write the following code, there is no issue:
myArray.append(object1)
But I want to write a loop to add all three. Again, very dumb, but I can't figure out how to insert the number in the name of the object as a variable. E.g., here was something I tried
let x = 3
for i in 1...x {
myArray.append(object[i])
}
This gives an error. The reason I want to do it using a loop, and not simply write in the three objects manually, is that I won't always loop three times. Sometimes I'll just want the first two objects, sometimes just the first.
I assume there's some easy way to do this, but when I search it tends to turn up more complex questions
hash_test.pl
#a=("f","a","b");
$K{"f"}{"aa"}=1;
$K{"a"}{"aa"}=1;
$k{"b"}{"bb"}=1;
foreach(#a){
#c= sort keys %{$k{$_}};
}
print "#c\n";
foreach(#c) {...}
perl hash_test.pl
bb
I want to keep the keys of the hash into an array, so that I can use the array as an input for the following statements.
But it seemed that the assay #c just only hold the last element.
Could anyone tell me why or help me to improve the script?
You assign the array every time in the foreach, thus overwriting it every time. So you end up with only having the last thing assigned to it. If you move the print inside the foreach you'll see that they are all there.
To store those keys you need to add them to the array, not assign the array. I've corrected the typo $k to $K, and changed aa that goes with f to ff (expecting it to be a typo as well).
my #c;
foreach my $el (#a) {
push #c, sort keys %{$K{$el}};
}
print "#c\n";
This prints the line: ff aa bb. Every time through the loop all keys found in the hash for a particular array element are added to #c, each as a separate element. So #c will contain all bottom-level keys across the whole data structure.
However, there is more that I would like to suggest.
Always use strict; and use warnings; This is not pedantry but it directly helps. I never write code without them. The typo would be caught here, for example.
Use descriptive variable names. Specifically, single-letter variable names are just too easy to confuse, unless in very short loops or where it is crystal clear what they are. (For example, a typo like this couldn't really happen.) Most importantly, the code is going to be far nicer to work with. That generally results in better code.
Please use good indentation and spacing. It helps a lot, in many ways.
A useful core package for nested data structures is Data::Dumper, which can print the whole thing nicely formatted so we can see it. Try to add to the end of your code
use Data::Dumper;
print Dumper(\%K);
There are yet others that do the same or similar.
Here is another way to do what you ask.
my #lowest_keys = map { sort keys %{$K{$_}} } #a;
I call them lowest_keys to emphasize that these are the ones from the last hash in your data structure, the bottom of it. The map applies processing in the block { ... } to each element of #a in turn, returning a list with all these results. (If any one result itself is a list, with more elements than one, it gets merged into the overall output list. So this may create the output list with many more elements than the input.) This list can then be assigned to an array, as above, or passed on to another function that expects a list as input, or interated over.
The map is generally used to transform an array into another, by doing to each element what is in { ... } block. Its close cousin grep is used to filter, so passing through only the elements of the input list for which the condition in { ... } evaluates to true, forming the output list. For example, filter out undefined array elements: my #good = grep { defined } #all
Variable names are case sensitive, so %K... and %k... are not the same.
Always use
use strict;
use warnings;
and declare your variables with my. That prevents you from making this kind of mistakes.
this is the problematic:
I got a master array, it's an array that have all the entities in the game.
When an entity (unit, building, etc) dies, I remove that entity from the array.
Now, I got other several arrays that are "subgroups" from that array. Like, enemyEntities, alliedEntities, movingEntities, etc. Everytime I create a new entity I add it to the corresponding array.
Everything works ok, but, when I remove one element from the master array, I'd like to somehow automatically remove it from the other arrays, let say, in an elegant way.
Any ideas?
Have a remove-method which takes care of it all. Make it first remove it from the master array, and then from each sub arrays (if the object is found). A nicer way of doing it might be to put all arrays in a another array, and do that to each of them in a loop.
I am working with an older and undocumented set of ActionScript (AS2) and I have found that an array, when looping through it the second time, does not give the proper results. It has been a while since I used ActionScript - does the array need to be reset before the second time through another for loop?
For instance PHP has reset() which returns the array's pointer back to the first item in the array.
There's is no such thing as pointers in ActionScript.
You can target each and every item in an Array by simply targeting it with myArray[index], and no pointer needs to be reset to be able to re-read it.
If your two loops produce different results, I would suggest looking into code that could change anything in it between the two loops or in the first one.
Maybe you could post it here ?
I'm sure others have already asked this, but is it possible to insert an element into the next available index of an array without using a for-loop to find that index first? Almost like a list.add() function but for arrays in C.
no, you will have to loop through the array.
If it's really list functionality you want you could implement a simple linked list instead of using arrays, for example like this: http://www.cprogramming.com/tutorial/c/lesson15.html