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basics.md

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Basics

"Function returning channel" is an important idiom. Rob Pike

Overview:

What comes with a basic "package pipe" (in some file named pipe.go)?

Which convention is used to name the functions (resp. methods)?

Note: ? represents the name of the (generic) type.

Create & generate

Pipe line 'til done

Spread & combine

Details

Functions and their names as they come with any basic "package pipe".

Note: All the following functions (except ?MakeChan) spawn a process.

Note: For brevity functions output is not mentioned. It's a ? channel.

Creator

Some like (or need) "Do-it-yourself": create a channel and write a generator

  • ?MakeChan() - aka make(chan ?) - returns a channel of ?.

Note: No process is spawned here, of course.

Generator

  • ?Chan... is the prefix common for generators.

Use some items, or some slices of items.

  • ?Chan( item ...?)
  • ?ChanSlice(itemS ...[]?)

Use some function which produces items together with an indication, typically a bool or an error.

  • ?ChanFuncNok(func() ?, bool)
  • ?ChanFuncErr(func() ?, error)

Typical candidates for such functions are

  • some iterator like Next() (item ?, ok bool)
  • some scanner busy scanning something 'till it encounters an error (e.g. io.EOF).

Pipe tube

  • ?Pipe... is the prefix common for pipe tubes.

Please remember: These return one receive-only channel (named out).

  • ?Pipe( func(item ?) ...) - apply operations (such as print/log)
  • ?PipeFunc( func(item ?) ? ...) - chain actions which return an item for an item

Mind You: Batteries are included with many special purpose pipe-tubes.

Finaliser

  • ?Done... is the prefix common for finalisers.

Please remember: These return a signal channel (named done), not a ? channel.

  • ?Done( func(item ?) ...) - apply operations (such as print/log) 'till close
  • ?DoneFunc( func(item ?) ? ...) - chain actions 'till close
  • ?DoneSlice() - returns a slice of all items received

Mind You: Batteries are included with special purpose finalisers such as freq.

One to Two

These return two channels (not just a single one, as usual):

  • ?Fork - send to any one (of the two)
  • ?Pair - send to both (in lockstep)

Notice the difference:

  • ?Fork enables two identical processes each to process part of the total workload concurrently.
  • ?Pair enables two different futures: two roads -typically different ones- to be pursued concurrently.

Use several times to spread out. Or see below.

Two to One

These accept two channels (and return one, as usual):

  • ?Fan2 - a binary fan-in.

Notice that ?Fan2 is kind of a closing bracket where ?Fork is the opening one.

One to Many & Many to One

Sure, two is not enough - more is needed.

Well, this is beyond basics, is it not?

Mind You: Batteries are included, and there are "the big brothers':

  • ?Fork becomes ?Strew
  • ?Pair becomes ?FanOut
  • ?Fan2 becomes ?FanIn or ?FanIn1

And there is more, such as ?Merge or ?Same.

Closures

  • ?Tube... - closures around ?Pipe*
  • ?Fini... - closures around ?Done*

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