Questions tagged [optional]
Optional is an immutable type that may contain a value or reference.
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Partial specialization of class template with minimal code duplication
I have a class template that stores an std::optional<T>. A very reduced version of the class template looks like this:
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C++ std::optional implementation
Took a shot at implementing a subset of std::optional functionality. A lot of core features are there but some things like converting constructors, etc are missing ...
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std::optional<std::size_t> correct values comparison [closed]
I need to compare two std::optional<std::size_t> variables, considering all possible cases(both std::nullopt or one of ...
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2
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Java spring controller method to trigger e-mail verification procedure [closed]
For readability sake, is it better to use optionals or write my code in an iterative manner?
Here's a route I'm working on, does this look readable do you?
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411
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Filtering an Option Result using a boolean Result in Rust
I'm trying to rewrite one of my pet projects in Rust, and when I was faced with the problem of filtering a Result<Option<T>, E> via a ...
3
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Rust idiomatic option handling
Is there a neater way of handling the option response from req.cookie() in this code block (line 3 onwards)? Id like to avoid the nested if statements, and multiple ...
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3
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Concatenating optional strings in Scala
I have two optional strings, any of them can be None. I want to create their combination with a delimiter between them if they both exist.
I expect to be able to come with a more concise and nicer ...
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2
votes
2
answers
99
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Treating Optional values
I have a situation when there could be and could not be values in database, which is why i return optional, so the response object that goes back to the UI could be different depending on the ...
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Using Java Optional.ofNullable() instead of if/else or ternary conditional [closed]
I've recently reviewed code twice, from two different authors, where the author has cleverly used Thingy z = Optional.ofNullable(x).orElse(y) rather than using, say,...
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A Start button handler
I was told my code contains a lot of force unwrapping. I thought it's okay to do that if I am sure that the value operated won't be nil:
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Updates or creates an entity based on if a value is present in an Optional
I need to get car info from a 3rd party web service and persist the data in my application DB. If my DB already has the car, I only update property values that may have changed. Otherwise, I create ...
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Maybe with a structural pattern matching interface
With a reference implementation for PEP 622 now available in a Jupyter playground, I decided to copy over my favourite feature of Rust in full to Python.
Note: this won't be released until Python 3.10 ...
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Unwrapping optionals for max of a 2D array in swift
I'm working in swift and I've got a custom class Array2D to handle fixed-width, two-dimensional arrays of integers. What I'm trying to do is write a simple, ideally-...
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C++ Optional Reference
Here is a good article on an optional reference type in C++. They discuss std::optional<T&>, but as that doesn't compile I have made my own.
One purpose ...
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Best practice to initialize instance variables for a POJO when values are null
I am using Java 8. I haven't found another question that fits mine exactly, and I've come across some conflicting information on best practices with what I'm trying to do.
I'm creating a POJO which ...
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Coalescing lvalue references to std-optionals
I want to coalesce (lvalue references to) optionals of the same type, in C++17:
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Is there better alternative to making an optional set of elements from iterable in java?
I'm feeling uneasy with this service method that I wrote:
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Is it worth to use if-else statement as Java optional pattern?
I came to a point while refactoring using if {} else {} code with Java optionals. While optimizing code it turned to a result to this:
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Force-unwrapped property as a contract
I have a class, which is meant to show a full screen modal controller with a set of actions (apart from actions it also has some static content, a lot of labels and images which are irrelevant, so I ...
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`std::optional` under C++14 v1
This is a first version of an implementation of std::optional it is supposed to compile under C++14. The public interface of the class is complete, but there are ...
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Change Kotlin optional-like style [closed]
I have next method in client
fun authUser(loginRequest: LoginRequest): String?
I need to implement next logic: check if user already exists - nothing to do,
if ...
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C++ Maybe<T> implementation
In order to improve my understanding of C++ template meta-programming, SFINAE, references, and overall class design, I've tried to implement a Maybe<T> class ...
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Haskell/Yesod - Butchering use of MaybeT
The following is some code that is used to provide the frontend with certain parameters when rendering a form. The parameters are conditional based around what data is being changed, ...
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Conditionally display an Action depending on whether or not a player is connected
Is there a nicer way to write the maybeWhen portion of displayConnectionAction ? I want to conditionally display an ...
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7
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2
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147
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Class template for the encapsulation of datasheet specifications using optionals
A couple of years ago I wrote a pair of class templates to encapsulate specifications which have one or more of a minimum, typical, and/or maximum value, e.g. on a datasheet like this one for the 741 ...
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Fed Singleton struct class from plist
I have a plist file which has URLs in it and struct class is feeding from this plist. This struct class has static variable which I use to reach URLs in every part of the app. My question is that I'm ...
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Append /src to an Optional path
My method getProjectDir() will return an Optional which contains the path to the project directory, or an empty container:
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73
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Handling multiple IO operations that return optional values
The following Haskell code reads a Pandoc document from the DB and then serves it to the user after making a transformation, after the first run it is stored in memory via ...
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Optional<T> implementation
I wrote an Optional<T> implementation in C++14 in order to support pre-C++17 compiler.
Differences to ...
user51787
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1
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149
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Grab first successful pair from a list of maps
I have a function that parses geographic coordinates through a list of different providers. In this case I want to look up two addresses. The main problem of this question is - given a List of of ...
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143
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Confirming whether a user is registered, using Optional class in Java 8
I start to learn Java 8 and I wondering is that kind of using Optional class is correct?
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223
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deep_ptr<T>; a header-only, deep copying, value semantic smart pointer for optionally defined types
Edit: final revision here
A couple days ago I posted a similar question here. Since then, I have refined the implementation a bit further, as the solution I had previously posited was a bit off ...
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Nullable<T>; header-only value semantics for forward declared types
Edit: I have refined the concept a bit further, and my new implementation can be found here
Motivation: I found myself with class members of forward declared types in a header, such as:
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C++ Nullable template class
Today I implemented a C++11 template class which allows for Nullable types. The reason for this is that std::optional is not yet available, (I use C++11/14) and I wanted to practice a bit, so I ...
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Variant optional to return error string or value
I needed a class with more information than optionals give, I need to know why the optional is not valid in error states. I used a Boost variant for this. Since this will be wrapping almost all of my ...
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Implementing a Maybe for multidimensional data
The scenario is we're working with a REST endpoint that gives us nice JSON objects. We're using requests, and everything works wonderfully. But one day you notice that data you though was always being ...
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81
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Concatenating multiple feedback messages
The goal is to build a String from a given set where Feedback is an interface and ...
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979
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An optional_ref<T>
I omitted all free operators but the equality comparisons ones because of verbosity. I am glad about any comments and improvements.
Motivation
I know that optional references are equivalent to ...
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Select a list from a 2D list, take the last item from its nearest non empty left neighbour and put it at its head
I've just got into Haskell a few days ago and I love it. I'm looking for some pointers and best practices on how to organise and write Haskell code specifically when it comes to managing errors, which ...
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399
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Maybe type implementation
This supposed to implement a Maybe type that can either hold a value T or "nothing". It's designed to work well with vectors (...
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Seamlessly migrating <experimental/optional> to <optional>
From this Stack Overflow answer, I learned that C++17 will have __has_include, which can
[make] migrating from experimental to std almost seamless
This still ...
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Filtering out empty Optionals
I want to convert my list of optional strings to a list of strings by getting rid of the empty Optionals.
Is there a shorter version for achieving this than the ...
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Optional Consumer for ifNotPresent
As Optional have only ifPresent and not have another function to be run in false case so I did the below class for that, please check it and give me your feedback:
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2
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C++ Optional Implementation
I haven't done much programming in C++, so I figured I'd try making an Optional class. I'm mainly concerned that I didn't follow good conventions or that I didn't ...
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1
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An attempt at implementing Maybe in C++11
I gave a shot at implementing Maybe for C++ and a slight twist in my implementation is that it uses thread_local static instance ...
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1
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427
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Simple/Naive Implementation of Identity and Maybe Monad in Elixir
This is my first crack at a identity monad and a maybe monad in Elixir:
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344
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Adding two values in a map, if they exist
My code looks like imperative style code. I want to make my code more functional. How I can rewrite my program so it become functional style code?
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