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Push iterator

As explained in Go by Example

A push iterator is an iteration abstraction in which a producer invokes a consumer with each successive value rather than having the consumer request values.

A push iterator lets a producer deliver sequence values by calling a consumer-supplied yield function. The consumer does not request the next value; it receives each value as the iterator produces it. A boolean returned by yield tells the iterator whether to continue or stop. section 6.3.1

In Go, iter.Seq[V] represents this pattern as a function that accepts yield func(V) bool. Instantiating it as iter.Seq[Result] creates an iterator for Result values, while a named Results type gives the package API a domain-specific name. section 6.3.1

Streaming HTTP results

SendN can return a Results iterator while sending multiple HTTP requests. A consumer supplies yield, receives each Result as it arrives, and can print a progress bar in real time. The package can therefore expose a synchronous-looking API while concurrency remains an internal implementation detail. section 6.0 section 6.3.1

Listing 6.3 Implementing the Results iterator (hit/result.go)
package hit

import (
    "iter"  #1
    "time"
)

// Results is an iterator for [Result] values.
type Results iter.Seq[Result]  #2

. . .

Inspect the Results declaration, which aliases iter.Seq[Result] for the hit package. section 6.3.1

How Go by Example covers it

How deep it goes
Defines yield-based control flow and generic Go types, then applies them to Result production without detailing the complete implementation.
Examples
Uses SendN, Result values, concurrent HTTP requests, and a real-time progress bar as concrete applications.
What you can do after
Apply it via iter.Seq by returning values through a consumer-provided yield function that can stop iteration.
How it connects
Connects iterators with concurrency, channels, HTTP requests, and the pipeline pattern.
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Go by Example. The section links point to the parts of the book it draws on.