Oh apologies for not taking a few moments to use the search facility. The linked github sounds extremely promising and certainly captures far more use cases than I initially intended.
Thanks Logan. David > On 11 Jul 2017, at 21:10, Logan Smyth <[email protected]> wrote: > > There's been talk of this before here and in > https://github.com/gilbert/es-pipeline-operator > <https://github.com/gilbert/es-pipeline-operator> among other places. Most > recently this was posted, which sounds like promising progress: > https://github.com/gilbert/es-pipeline-operator/issues/33#issuecomment-306986211 > > <https://github.com/gilbert/es-pipeline-operator/issues/33#issuecomment-306986211> > > On Tue, Jul 11, 2017 at 1:02 PM, David White <[email protected] > <mailto:[email protected]>> wrote: > Piping is useful when composing many small pure functions together, one > problem with this is the evaluation needs to be read from the inner most > expression value in reverse to the outer most function call. Given the > following statement we can see that it would be read as 'call math round then > call math square then pass in PI', whereas the order of execution is in > reverse. > > ```javascript > const myNumber = Math.round(Math.sqrt(Math.PI)); > ``` > > Unix has long provided a piping mechanism to achieve that, for example: `ps > aux | grep node`, as well as F# and the Elixir programming language, both > provide the `|>` pipe greater-than operator which is very readable. > > My proposal would be to use the slightly more verbose `|>` pipe-greater than > syntax, it provides a convenient direction of travel for the expression on > the left side, into the expression on the right, F# also provides a `<|`, > which pipes in the opposite direction though I’ve not really seen very good > use cases for this operator. > > ```javascript > const myNumber = Math.PI |> Math.sqrt |> Math.round; > ``` > > The left side of the operator should always be a primitive data type or data > structure, these could be any of the following: `Boolean`, `Null`, > `undefined`, `Number`, `String`, `Symbol` or `Object`. Since functions are > standard objects they can be passed in as the initial value, as long as the > function on the right handles the calling on that function. > > It also provides a way to either log, process, or do anything with the data > from the last expression on the left at various stages of the execution > without adding additional brackets in and around the calls, for example. > > ```javascript > function logger (callback) { > return function (value) { > callback(value); > return value; > }; > } > > Math.PI > |> logger(console.log); > |> Math.sqrt > |> logger(console.log); > |> Math.round > |> logger(console.log); > ``` > > While a slightly contrived example as we certainly wouldn't write code that > looks like: > > ```javascript > logger(Math.round(logger(Math.sqrt(logger(Math.PI))))); > ``` > > We would instead assign to variables at each stage of execution: > > ```javascript > const PI = Math.PI; > logger(PI); > > const squaredPI = Math.sqrt(PI); > logger(squaredPI); > > const roundedSquaredPI = Math.round(squaredPI); > logger(roundedSquaredPI); > ``` > > However with this clarity we have unfortunately had to create additional > constants within this lexical block, whereas simple value passing between > pure functions provides a very clean and readable approach and allows easier > updates in the future if we wanted to add additional processing within the > chain, for example Express middleware composition. > > Would love to hear some thoughts on this? > > David > > * [F# pipe > operator](https://docs.microsoft.com/en-gb/dotnet/fsharp/language-reference/functions/index#function-composition-and-pipelining > > <https://docs.microsoft.com/en-gb/dotnet/fsharp/language-reference/functions/index#function-composition-and-pipelining>) > * [Elixir pipe > operator](https://elixir-lang.org/getting-started/enumerables-and-streams.html#the-pipe-operator > > <https://elixir-lang.org/getting-started/enumerables-and-streams.html#the-pipe-operator>) > * [Unix pipeline](https://en.wikipedia.org/wiki/Pipeline_(Unix) > <https://en.wikipedia.org/wiki/Pipeline_(Unix)>) > > _______________________________________________ > es-discuss mailing list > [email protected] <mailto:[email protected]> > https://mail.mozilla.org/listinfo/es-discuss > <https://mail.mozilla.org/listinfo/es-discuss> >
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