Yield
A language construct that yields control from a computation, optionally passing a value to another context, and may allow the suspended computation to continue later.
Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
A JavaScript keyword used inside generator functions to pause execution and produce or receive a value.
- How it is used
- Uses `yield` to pause generator functions, send values outward, and receive values when execution resumes.
- How deep it goes
- Works through generator lifecycle and `next()` results, including the unused first argument, while leaving broader generator applications for later.
- Examples
- Uses successive yields, infinite numbers, Fibonacci numbers, adaptive simulation objects, and a timed CPU turn.
- What you can do after
- Build it from scratch: create generators that yield requested values and accept feedback through `next()`.
Secrets of the JavaScript Ninja, Second Edition
An expression in a JavaScript generator that yields a value and evaluates to a value supplied when execution resumes.
- How it is used
- Uses yield to produce generator values on request while suspending execution between requests.
- How deep it goes
- Explains yield through iterator results and resumed expressions, then shows delegation and injected exceptions; stops short of runtime internals.
- Examples
- Uses weapon sequences, generator-to-generator delegation, and a two-way exchange through next().
- What you can do after
- Build it from scratch by yielding a sequence and receiving a value when the generator resumes.
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The Well-Grounded Rubyist, Fourth Edition
yield is a Ruby keyword that transfers execution to the block associated with the currently running method and then resumes the method afterward.
- How it is used
- Enables iterator methods to run caller-supplied blocks and resume their own work afterward.
- How deep it goes
- Works through repeated yielding, values passed to blocks, block results, and method returns using custom iterator implementations.
- Examples
- Uses `my_loop`, `Integer#my_times`, `Array#my_map`, and an indented-list generator to show successive uses of `yield`.
- What you can do after
- Build it from scratch: write iterators that pass values to blocks, collect their results, and choose a method return value.
Read how The Well-Grounded Rubyist, Fourth Edition explains yield →
Python Workout: 50 ten-minute exercises
yield is a Python statement that produces a value from a generator function while suspending its execution until the next value is requested.
- How it is used
- Deploys yield to write lazy generators that supply iterable values incrementally.
- How deep it goes
- Explains suspension, resumption, automatic termination, and retained locals, while contrasting generators with explicit iterator classes.
- Examples
- Demonstrates numbered values, filtered file lines, retained timing state, and chaining multiple iterables.
- What you can do after
- Builds generators that stream values, preserve state, filter input, and combine iterables without implementing iterator methods manually.
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C# Concurrency: Asynchronous and multithreaded programming
Yield return is a C# language feature that produces an iterator element and suspends execution until the iterator advances again.
- How it is used
- Uses iterator methods to generate sequences on demand and establish compiler-transformation fundamentals for async/await.
- How deep it goes
- Explains generated enumerable and enumerator classes, resumable chunks, state tracking, MoveNext, and asynchronous iterator extensions.
- Examples
- Demonstrates list-based and yield-based sequences producing 1 and 2, then extends the pattern to asynchronous data and work queues.
- What you can do after
- Build iterator methods and asynchronous sequences, consume them with foreach or await foreach, and understand their generated control flow.
Read how C# Concurrency: Asynchronous and multithreaded programming explains yield →
Python Workout, Second Edition
yield is a Python statement or expression that produces a value from a generator function while suspending its execution for later resumption.
- How it is used
- Builds lazy iterators that return one value at a time when requested.
- How deep it goes
- Explains suspension, resumption, automatic termination, and retained local state across iterations.
- Examples
- Uses a three-value foo generator, for-loop consumption, iterable chaining, and elapsed-time reporting.
- What you can do after
- Build it from scratch using generator functions that yield sequences while preserving state between requests.
.NET in Action, Second Edition
yield return is C# iterator syntax that produces an element and suspends execution until the next element is requested.
- How it is used
- Generates xUnit MemberData cases and forwards processed elements through synchronous or asynchronous enumerations.
- How deep it goes
- Explains one-at-a-time enumeration, collection avoidance, object-reuse pitfalls, and async-stream composition without detailing compiler-generated state machines.
- Examples
- Demonstrates independent Sudoku boards for theory tests and enriched Comic objects returned from asynchronous searches.
- What you can do after
- Build it from scratch to generate test cases or stream transformed asynchronous results one element at a time.
Python How-To
The yield keyword pauses a generator function, provides a value to its caller, and allows execution to resume later from the pause point.
- How it is used
- Deploys yield to create generators that render values lazily during iteration.
- How deep it goes
- Explains pausing, resumption, state retention, exhaustion, next, and StopIteration, while deferring coroutine details.
- Examples
- Uses perfect-square generators, manual next calls, generator expressions, and sums to demonstrate lazy production and consumption.
- What you can do after
- Build it from scratch by writing generator functions that yield values incrementally and resume correctly across iteration.
Idiomatic Rust
A yield statement suspends a coroutine and optionally supplies a value to its caller.
- How it is used
- Passes values from a suspended coroutine to its caller, including when building iterators over data streams.
- How deep it goes
- Traces yielding through resume calls and coroutine states, with a basic example; defers more complex scenarios.
- Examples
- Demonstrates yielding π before returning a string, and yielding numbered file lines for an iterator.
- What you can do after
- Build a coroutine closure that yields values on resume and returns a completion value.
Fabulous Adventures in Data Structures and Algorithms
yield return is C# iterator-block syntax that produces sequence elements on demand during enumeration.
- How it is used
- Generates permutation sequences incrementally during enumeration.
- How deep it goes
- Explains deferred execution, recursive implementation, desugared calls, and enumeration complexity.
- Examples
- Demonstrates recursive change-ringing permutations and a yield-based InsertAt helper.
- What you can do after
- Apply it via C# iterator methods to produce sequence elements on demand and analyze enumeration costs.
Read how Fabulous Adventures in Data Structures and Algorithms explains yield →
Related concepts
- generatorused by · A generator is a language construct or computation that produces values incrementally on demand, typically suspending and resuming while preserving its state.
- return statementcontrasts with · A return statement ends the current function or routine invocation and optionally supplies its result to the caller.
- nextused by · An iterator operation that advances an iterator and returns its next value or result, with behavior on exhaustion determined by the API.
- async/awaitcontrasts with · Async/await is language syntax for expressing asynchronous computations that suspend at awaited operations and resume when they can proceed without blocking the execution thread.
- suspending functionuses · A suspending function can pause and later resume execution without blocking the underlying thread.
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