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Questions tagged [enumerable]

"enumerable" refers to an ordering scheme that enables items in a set, sequence or collection to be readily addressed or traversed.

Enumerable is a Ruby module which can be included in other Ruby classes in order to allow iteration via #map/#collect, #select, #each, and so on.

Enumerable also manifests as the class Enumerator (documentation), which is returned when an iteration method is called without a block (e.g., array.each instead of array.each { |x| puts x }).

Enumerable objects may also utilize chained iteration, e.g., array.each.with_indices instead of array.each_with_indices.

Ruby 2.0 also introduces the concept of lazy enumeration.

In .NET, Enumerable is the class that wraps most common LINQ extension methods.

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How to create a TypeScript @enumerable(false) decorator for a property

I want to create a decorator in TypeScript in order to be able to make a class property not enumerable. I found an example of @enumerable here: https://www.typescriptlang.org/docs/handbook/decorators.html#method-decorators but that only seems to…
mvermand
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Performance of Enumerable.Range vs for loop

I wondered what the performance overhead is of using Enumerable.Range was against using a foreach loop. For example: var stringArray = Enumerable.Range(0, 4).Select(i => string.Empty).ToArray(); VS. var stringArray = new string[4]; for (int i = 0;…
jolySoft
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Enumerate existing text in Vim (make numbered list out of existing text)

I have a source document with the following text Here is a bunch of text ... Collect underpants ??? Profit! ... More text I would like to visually select the middle three lines and insert numbers in front of them: Here is a bunch of text ... 1.…
user1717828
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Sort an enumerable in descending order

What's the best way to sort an Enumerable in descending order? I've been doing @array.sort.reverse or @array.sort_by{|song| song.title }.reverse I suppose I could do something like @array.sort{|a, b| b.title <=> a.title}, but I find this hard to…
Tom Lehman
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How to get Enum object by value in C#?

I recently encountered a case when I needed to get an Enum object by value (to be saved via EF CodeFirst), and here is my Enum: public enum ShipmentStatus { New = 0, Shipped = 1, Canceled = 2 } So I needed to get ShipmentStatus.Shipped object…
mikhail-t
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refer an enumerator value with specified index

Assume I have an enumerable object enum and now I want to get the third item. I know one of a general approach is convert into an array and then access with index like: enum.to_a[2] But this way will create a temporary array and it might be…
shouya
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Returning the differences between two enumerables

I'm trying to determine the differences between two collections. private ObservableCollection _objectList = null; private ObservableCollection _cachedObjectList = null; SomeObject implements IEquatable I'm using…
Michael G
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Why does repeated Enumerable to Observable conversion block

This is a rather educational, out of curiosity question. Consider the following snippet: var enumerable = Enumerable.Range(0, 5); var observable = enumerable.ToObservable(); var enu =…
Martin Zikmund
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Can a Ruby method accept either a block OR an argument?

I'm doing the lessons on The Odin Project and now I have to write myself a new #count method (with another name) that behaves like the normal one from the Enumerable module. The documentation on count says the following…
Nikolay D
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Why would #each_with_object and #inject switch the order of block parameters?

#each_with_object and #inject can both be used to build a hash. For example: matrix = [['foo', 'bar'], ['cat', 'dog']] some_hash = matrix.inject({}) do |memo, arr| memo[arr[0]] = arr memo # no implicit conversion of String into Integer…
mbigras
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Ruby Enumerable: first truthy value of a block

In ruby we can do something like: stuff_in_trash.detect(&:eatable?) => :pack_of_peanuts stuff_in_trash.detect(&:drinkable?) => nil But what if we are interested in the value of the block the first time it is truthy, rather than the first item for…
sunless
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C# infinite iteration

Is there anything similar in C# to Java's Stream.iterate? The closest thing I could find was Enumerable.Range but it is much different. The reason I'm asking is that I've been just watching some presentation about good programming principles and…
SOReader
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Does `map` use `each` or not?

In Ruby, the Enumerable module mixes into collection classes and relies on the class serving up an each method which yields each item in the collection. Okay, so if I want to use Enumerable in my own class, I'll just implement each [1]: class…
Erik Trautman
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Elixir: how to make struct enumerable

I have a struct: my_struct = %MyStruct{a: 1, b: 2} how do I make it enumerable, so I can use the Enum methods on it?
tldr
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How does to_enum(:method) receive its block here?

This code, from an example I found, counts the number of elements in the array which are equal to their index. But how ? [4, 1, 2, 0].to_enum(:count).each_with_index{|elem, index| elem == index} I could not have done it only with chaining, and the…
Dean Radcliffe
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