DEV Community: chenge

A simple concise guide for Go in Chinese

chenge — Tue, 14 May 2019 03:48:04 +0000

Go is a simple language so we like simple guide. Here is one written in Chinese. You can read in one or two days. If you don't know Chinese you can ask help from Google translate.

hello world

Study of Programming Languages Not to Learn in 2019

chenge — Thu, 18 Apr 2019 23:19:56 +0000

Ruby rank #18，Elixir #7， Erlang #3

What does tech stacks mean in following pic?

-->link

Simple Idea for Improving Error Handling of Go

chenge — Thu, 11 Apr 2019 08:34:41 +0000

Following is normal code, repeat too much, not so good.

_, err = fd.Write(p0[a:b])
if err != nil {
    return err
}
_, err = fd.Write(p1[c:d])
if err != nil {
    return err
}
_, err = fd.Write(p2[e:f])
if err != nil {
    return err
}

Improved code:

type errWriter struct {
    w   io.Writer
    err error
}

func (ew *errWriter) write(buf []byte) {
    if ew.err != nil {
        return
    }
    _, ew.err = ew.w.Write(buf)
}

ew := &errWriter{w: fd}
ew.write(p0[a:b])
ew.write(p1[c:d])
ew.write(p2[e:f])
if ew.err != nil {
    return ew.err
}

It looks better now by adding another level.

Do you think so?

End and Ref

Repeat Error Handling in Go, a Chinese post.

Nice Video: First Day of Emacs

chenge — Sun, 27 Jan 2019 22:23:01 +0000

First words, the teacher is great. But he used Chinese, if you don't konw Chinese and you are patient you can watch and guess his idea. The slides are English.

I knew a little Emacs. After this video I feel more confidence. The teacher taught from basics.

The Org mode and company package are useful. Org mode can fold topics easily.

Why Emacs

I use MS code and a little vim now. I still want to try emacs because I think it's fun and can practice some lisp.

If you prefer menu you can try spacemacs which is more friendly for new learners. It simply uses space key to give you a menu.

Haskell in One Slide

chenge — Sat, 26 Jan 2019 10:46:57 +0000

This pic is from the video by professor Simon and explains the function syntax clearly.

Typeclass(Interface) is Kernel Concept of Haskell Functor, Monad These Weird

chenge — Sat, 26 Jan 2019 09:35:53 +0000

In short, typeclass is just like interface, so it's not so hard to understand.

Let's see some code about Maybe functor, functor has a special map function:

class Functor Maybe where
    fmap :: (a -> b) -> Maybe a -> Maybe b

instance Functor Maybe where
    fmap func (Just x) = Just (func x)
    fmap func Nothing  = Nothing

Functor is a typeclass.
Applicative Functor extends Functor.
Monad extends Applicative.

class Applicative m => Monad m where
    return :: a -> m a
    (>>=) :: m a -> (a -> m b) -> m b

And another one Monoid is a math concept. It's a typeclass too.

They are all typeclasses.

ref

Functor、Applicative 和 Monad(Chinese)

Learn You a Haskell for Great Good!

Book Notes: Learn You a Haskell for Great Good!

Nested Software ・ Dec 4 '18

#haskell #functional #monad #javascript

A Good Video for Haskell Monad

chenge — Fri, 25 Jan 2019 13:06:53 +0000

A good video although I don't understand monad now.

A Fun Tool: Curl to Program

chenge — Fri, 25 Jan 2019 12:28:16 +0000

Convert curl syntax to Python, Node.js, R, PHP, Go

It support python and other languages.

https://curl.trillworks.com/

A Nice Short Video for Basic Haskell

chenge — Fri, 25 Jan 2019 10:20:13 +0000

Haskell Basics - FunFunFunction

What's the "//?" in the Code Editor

chenge — Wed, 23 Jan 2019 09:50:18 +0000

"//?" can eval instantly. I saw it in this short JS teaching video. It seems cool. What plugin is it?

Meta-programming for Dummies - RedDotRubyConf 2017

chenge — Tue, 22 Jan 2019 21:17:34 +0000

A nice video for meta-programming.

Cool CLIs in Elixir with IO.write/2

chenge — Mon, 21 Jan 2019 07:00:23 +0000

Today I read this, it told us with 3 simple and fun samples: clock, counter and progress bar.

defmodule Progress do
  @rounding_precision 2
  @progress_bar_size 50
  @complete_character "█"
  @incomplete_character "░"

  def bar(count, total) do
    percent = percent_complete(count, total)
    divisor = 100 / @progress_bar_size

    complete_count = round(percent / divisor)
    incomplete_count = @progress_bar_size - complete_count

    complete = String.duplicate(@complete_character, complete_count)
    incomplete = String.duplicate(@incomplete_character, incomplete_count)

    "#{complete}#{incomplete}  (#{percent}%)"
  end

  defp percent_complete(count, total) do
    Float.round(100.0 * count / total, @rounding_precision)
  end
end

total = 50

Enum.each(1..total, fn task ->
  IO.write("\r#{Progress.bar(task, total)}")
  Process.sleep(50)
end)

IO.write("\n")