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Tweak wording in README. Better code fragment.

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Mike Thompson 2017-10-13 12:18:29 +11:00
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README.md
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@ -65,14 +65,15 @@ Perhaps:
You might already know that ClojureScript is a modern lisp, and that
lisps are **homoiconic**. If not, you do now.
That homoiconic bit is significant. It means you program in a lisp by creating and
This homoiconic bit is significant. It means you program in a lisp by creating and
assembling lisp data structures. Dwell on that for a moment. You are **programming in data**.
The functions which later transform data, themselves start as data.
The functions which later transform data, themselves start as data. In the beginning,
there was only data.
Clojure programmers place particular
emphasis on the primacy of data. When they aren't re-watching Rich Hickey videos,
and wishing their hair was darker and more curly,
they meditate on aphorisms like **Data is the ultimate in late binding**.
Clojure programmers place particular emphasis on the primacy of data, and
they like to meditate on aphorisms like **Data is the ultimate in late binding**.
(Less productively, they also like re-watching Rich Hickey videos,
and wishing their hair was darker and more curly)
I cannot stress enough what a big deal this is. It may seem
like a syntax curiosity at first but, when the penny drops for
@ -317,7 +318,7 @@ register this `h` as the handler for `:delete-item` events, like this:
```clj
(re-frame.core/reg-event-fx ;; a part of the re-frame API
:delete-item ;; the kind of event
h) ;; the handler function for this kind of event
h) ;; the handler function for this kind of event
```
`h` is written to take two arguments:
@ -329,11 +330,11 @@ it returns a map of `effects` - a description of those changes.
Here's a sketch (we are at 30,000 feet):
```clj
(defn h ;; choose a better name like delete-item
[coeffects event] ;; args: db from coeffect, event
(defn h ;; maybe choose a better name like `delete-item`
[coeffects event] ;; `coeffects` holds the current state of the world.
(let [item-id (second event) ;; extract id from event vector
db (:db coeffects)] ;; extract the current application state
{:db (dissoc-in db [:items item-id])})) ;; effect is change app state
{:db (dissoc-in db [:items item-id])})) ;; effect is "change app state to ..."
```
re-frame has ways (described in later tutorials) to inject necessary aspects
@ -342,12 +343,12 @@ event handlers need different "things" to get their job done. But
current "application state" is one aspect of the world which is
invariably needed, and it is available by default in the `:db` key.
BTW, here is a more idiomatic rewrite of `h` which uses "destructuring" of the args:
BTW, here is a more idiomatic rewrite of `h` which uses `destructuring` of the args:
```clj
(defn h
[{:keys [db]} [_ item-id]] ;; <--- new: obtain db and id directly
{:db (dissoc-in db [:items item-id])}) ;; same as before
[{:keys [db]} [_ item-id]] ;; <--- new: obtain db and id directly
{:db (dissoc-in db [:items item-id])}) ;; same as before
```