DEV Community: Regular 🍟

Prime Sieve Algorithm Cheat Sheet

Regular 🍟 — Fri, 18 Jun 2021 07:22:14 +0000

Sieve of Eratosthenes

bool isPrime[MAXN];
void sieve_of_Eratosthenes(int n) {
  isPrime[0] = isPrime[1] = true;

  for (int i = 2; i <= n; ++i)
    if (!isPrime[i])
      for (int j = i << 1; j <= n; j += i)
        isPrime[j] = true;
}

Sieve of Euler

int prime[MAXN];
bool isPrime[MAXN];
void sieve_of_Euler(int n) {
  isPrime[0] = isPrime[1] = true;

  int pNum = 0;
  int upto = n >> 1 | 1;
  for (int i = 2; i <= upto; ++i) {
    if (!isPrime[i])
      prime[++pNum] = i;
    for (int j = 1; j <= pNum && prime[j] * i <= n; ++j) {
      isPrime[prime[j] * i] = true;
      if (!(i % prime[j]))
        break;
    }
  }
}

*Sieve of Sundaram

#include <cstdio>

const int MAXN = 10000010;

bool isPrime[MAXN];

void sieve_of_Sundaram(int n) {
  isPrime[0] = true;
  for (int i = 1; i <= n; ++i) {
    int upto = (n - i) / (i << 1 | 1);
    for (int j = 1; j <= upto; ++j)
      isPrime[i + j + (i * j << 1)] = 1;
  }
}

int main() {
  int n;

  scanf("%d", &n);
  sieve_of_Sundaram(n);

  for (int i = 2; i <= n; ++i) {
    if (i & 1 && !isPrime[i >> 1])
      printf("%d ", i);
  }
}

Source Code: github

Add a DM Button to Your Tweet

Regular 🍟 — Tue, 27 Apr 2021 07:10:08 +0000

Inspired by my twitter friends, I intended to simplify the way of creating Direct Message Button.

What the Twitter DM Button is?

The Twitter DM Button is an elegant way for you to help others send DM to you. It's default content can be customized.

and it's effect(on mobile device):

default message is "hello, 🍟

~~~" here.

It seems that it doesn't work out of twitter environment(like web or mobile app), but you can see the origin tweet by clicking it.

{% twitter 1386690916694380551 %}

How I Started

At the beginning, I analyzed the link of this button.

https://twitter.com/messages/compose?text=hello,%20%F0%9F%8D%9F~~~

&recipient_id=1190406529922416641

Easy to find, the text= part defines the default message and recipient_id= is your twitter id(not handle)

so it's not hard to combine a link like this by ruby


ruby
def make_permlink(content, twitter_id)
  baselink = "https://twitter.com/messages/compose?"
  greetings = URI.encode content
  "#{baselink}text=#{greetings}&recipient_id=#{twitter_id}"
end

URI.encode convert spaces to %20 or something.

How it Ended

I decided to share this "widget" and obviously sharing .rb files is not a good idea. So I began to write a web app.

At first I chose Rails but it's like using a cannon to hit a mosquito. So I take some time learning another web framework Sinatra and use it.

Its simplicity fits this simple web app best. You can see the core code of this project:


ruby
# twitter.dm.rb

get '/' do
  erb :index
end

post '/' do
  unless params[:handle].empty? or params[:content].empty?
    @permlink = make_permlink params[:content], params[:handle]
  end
  erb :index
end

and view


erb
# views/index.erb

<% if @permlink %>
  <div>
    Your DM Button's link is:
    <%= escape_html(@permlink) %>
  </div>
<% end %>

The Repo: vonhyou/get-twitter-dm-btn

Web App: Twitter DM Button

ps: I am not familiar with the front-end, if you are interested, welcome to pr 🥺

Accurately Judge Data Types by Using Regex

Regular 🍟 — Wed, 21 Apr 2021 15:43:23 +0000

Time: 2021-04-12 11:56 UTC+8:00

Author: Me

It's not easy to judge a string's content's type in a normal way. So, it's time for regular expressions.

Integers

isInteger       = /^-?\d+$/                             # for integers
isPositiveInt   = /^[0-9]*[1-9][0-9]*$/     # for positive integers
isNegativeInt   = /^-[0-9]*[1-9][0-9]*/     # for negative integers
isNonPosiInt    = /^((-\d+)|(0+))$/             # for non-positive integers
isNonNegaInt    = /^\d+/                                    # for non-negative integers

Floats

isFloat         = /^(-?\d+)(\.\d+)?/                                # for floats
isPositiveFloat = /^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*))$/                                                                                         # for positive floats
isNegativeFloat = /^(-(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*)))$/                                                                               # for negative floats
isNonPosiFloat  = /^((-\d+(\.\d+)?)|(0+(\.0+)?))$/  # for non-positive floats
isNonNegaFloat  = /^\d+(\.\d+)?$/                                       # for non-negative floats

Regex for Verifying Email Address

Regular 🍟 — Wed, 21 Apr 2021 15:41:21 +0000

Time: 2021-03-29 23:07 UTC+8:00

Author: vonhyou

The fully RFC 822 complaint regex is too complex to use, here are some simplified regex to do that.

Regex from Ruby on Rails Tutorial (by Macheal Hartl)

VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i

But the author gave us a symbol which is invalid but passed it

"foo bar"@example.com

Several solutions given by Stack Overflow

# Falls to subdomain
VALID_EMAIL_REGEX = /\A([\w+\-]\.?)+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i

VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i

Standard Library Ruby version >= 2.2.1

URI::MailTo::EMAIL_REGEXP

Using build-in regex is the most efficient way.

The full version of it is:

>> URI::MailTo::EMAIL_REGEXP
=> /\A[a-zA-Z0-9.!\#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\z/

Appendix:

Useful tool rubular.com

Regex from ex-parrot

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ 
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\
r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[
 \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)
?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t]
)*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[
 \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)
*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+
|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r
\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t
]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031
]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](
?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?
:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?
:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?
[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|
\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>
@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"
(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[
\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-
\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(
?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;
:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([
^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"
.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\
]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\
[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\
r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]
|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \0
00-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\
.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,
;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?
:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[
^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]
]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(
?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[
\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t
])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t
])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?
:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|
\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:
[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\
]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)
?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["
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?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>
@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[
 \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,
;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:
\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[
"()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])
*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])
+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\
.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)

My Minimal Lisp Interpreter

Regular 🍟 — Mon, 19 Apr 2021 14:50:21 +0000

Time: 2021-04-03 23:44

Author: vonhyou

The source code on GitHub: vonhyou/lisp-interpreter

My log of implementing a lisp interpreter.

Try Scheme Lisp

I'll try a famous lisp dialect at first.

Install `mit-scheme` on macOS

MIT/GNU Scheme is an implementation of the Scheme programming language, providing an interpreter, compiler, source-code debugger, integrated Emacs-like editor, and a large runtime library.

Official website: www.gnu.org/software/mit-scheme

Install by Homebrew

$ brew install mit-scheme

Run Interpreter in Terminal

$ scheme --version
MIT/GNU Scheme 11.2
Copyright (C) 2020 Massachusetts Institute of Technology
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.

Image saved on Wednesday March 10, 2021 at 2:52:49 PM
  Release 11.2 || SF || LIAR/x86-64

Moriturus te salutat.

Use Scheme Lisp as a Calculator

1 ]=> (+ 1 2 3 4 5)

;Value: 15

1 ]=> (/ 12 7)

;Value: 12/7

1 ]=> (* 1 2 3 4)

;Value: 24

1 ]=> (/ (+ 3 2) (* 5 7))

;Value: 1/7

1 ]=> (quotient 7 3)

;Value: 2

1 ]=> (modulo 7 3)

;Value: 1

1 ]=> (sqrt 2)

;Value: 1.4142135623730951

1 ]=> (exact->inexact (/ 7 3))

;Value: 2.3333333333333335

1 ]=> (expt 3 12)

;Value: 531441

Try cons and list

1 ]=> (cons 1 2)

;Value: (1 . 2)

1 ]=> (cons 1 (cons 2 3))

;Value: (1 2 . 3)

1 ]=> '(1 2 2 3 4)

;Value: (1 2 2 3 4)

1 ]=> (car (cdr (cdr '(1 2 3 4))))

;Value: 3

Define and Let

1 ]=> (define var 10)

;Value: var

1 ]=> var

;Value: 10

1 ]=> (define func (lambda () "hello, world!"))

;Value: func

1 ]=> (func)

;Value: "hello, world!"

Condition

1 ]=> (if #t "true" "false")

;Value: "true"

1 ]=> (define (level grade)
        (cond
        ((> grade 90) 4.0)
        ((> grade 80) 3.5)
        ((> grade 60) 2.0)
        (else 0)))

;Value: level

1 ]=> (level 83)

;Value: 3.5

Implement and Release of My Lisp

Design-> Implement-> Release

Preparations: Design

I'll take some time to design my minimum Lisp.

Keywards of My Lisp

def
cons
car and cdr
quote
if
lambda

Operator of My Lisp

+, -, *, /, %
and, or, not
==, !=, <, <=, >, >=
&, |, ^, ～

Build-in Methods of My Lisp

min and max
print

Parse

# in module Prolisp

def self.tokenize(program)
  # Convert scripts to token lists
  program.gsub('(', ' ( ').gsub(')', ' ) ').split
end

def self.make_list(tokens)
  lst = []
  lst << read_tokens(tokens) while tokens[0] != ')'
  tokens.shift
  lst
end

def self.read_tokens(tokens)
  # read expressions from token
  raise SyntaxError, 'Unexpected EOF' if tokens.empty?

  case token = tokens.shift
  when '('
    make_list tokens
  when ')'
    raise SyntaxError, "Unexpected ')'"
  else
    atom token
  end
end

def self.atom(token)
  # Analyse numbers and symbols
  case token
  when /\d/
    (token.to_f % 1).positive? ? token.to_f : token.to_i
  else
    token.to_sym
  end
end

Global env

# in module Prolisp
def self.make_global
  @global_env ||= begin
    ops = %i[== != < <= > >= + - * / % & | ^ ～]
    ops.inject({}) do |sp, op|
      sp.merge op => ->(*args) { args.inject(&op) }
    end
  end

  @global_env.merge! quote: ->(*args) { args.to_a }
  @global_env.merge! cons:  ->(*args) { args.to_a }
  @global_env.merge! car:   ->(arr)   { arr[0] }
  @global_env.merge! cdr:   ->(arr)   { arr[1..-1] }
  @global_env.merge! print: ->(arg)   { p arg }
  @global_env.merge! min:   ->(arr)   { arr.min }
  @global_env.merge! max:   ->(arr)   { arr.max }
  @global_env
end

Eval

# in module Prolisp
  def self.lisp_eval(elem, env = make_global)
    if elem.instance_of? Symbol
      env[elem]
    elsif elem.instance_of?(Integer) || elem.instance_of?(Float)
      elem
    elsif elem[0] == :def
      _, sym, exp = elem
      env[sym] = lisp_eval(exp, env)
    elsif elem[0] == :if
      _, cod, if_true, if_false = elem
      exp = lisp_eval(cod, env) ? if_true : if_false
      lisp_eval exp, env
    elsif elem[0] == :lambda
      _, params, body = elem
      ->(*args) { lisp_eval body, env.merge(Hash[params.zip(args)]) }
    elsif elem[0] == :and
      lisp_eval(elem[1], env) && lisp_eval(elem[2], env)
    elsif elem[0] == :or
      lisp_eval(elem[1], env) || lisp_eval(elem[2], env)
    elsif elem[0] == :not
      !lisp_eval(elem[1], env)
    else
      func, *args = elem.map { |e| lisp_eval e, env }
      func.call(*args)
    end
  end

REPL

# in module Prolisp
  def self.repl(prompt = 'prol ƛ>> ')
    puts $copyleft
    loop do
      print prompt
      val = lisp_eval(parse(gets.chomp))

      print_value val unless val.nil? || val.instance_of?(Proc)
    end
  end

  def self.print_value(value)
    puts ";Value: #{value}"
  end
end

Usage

$ git clone git@github.com:vonhyou/lisp-interpreter.git
$ cd ./lisp-interpreter
$ ruby ./prol.rb

"Feature" of `Prol`

Basic functions as a minimal lisp
No support for String
Unable to define local variables
Comments are not allowed

References

Yet Another Scheme Tutorial, http://www.shido.info/lisp/idx_scm_e.html
(How to Write a (Lisp) Interpreter (in Python)), http://norvig.com/lispy.html

A Better Way to Deploy Rails app on Heroku

Regular 🍟 — Mon, 19 Apr 2021 14:27:55 +0000

Time: 2021-04-03 23:44 UTC+8:00

Author: vonhyou

This article introduces the professional way of deploying Rails app on Heroku.

Force SSL

Modify the file config/environments/production.rb in your Rails app:

# Uncomment this 
config.force_ssl = true

Heroku provide free ssl certificate and it's not necessary to do something else.

Switch to Puma

Add a gem called puma to the Gemfile and install it.
Rewrite the file config/puma.rb

# Puma configuration file.
max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
threads min_threads_count, max_threads_count
port        ENV.fetch("PORT") { 3000 }
environment ENV.fetch("RAILS_ENV") { ENV['RACK_ENV'] || "development" }
pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
workers ENV.fetch("WEB_CONCURRENCY") { 2 }
preload_app!
plugin :tmp_restart

Create Procfile

$ touch ./Procfile

Write Procfile

web: bundle exec puma -C config/puma.rb

Configurate database for production

# SQLite. Versions 3.8.0 and up are supported.
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
#
default: &default
  adapter: sqlite3
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  timeout: 5000

development:
  <<: *default
  database: db/development.sqlite3

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: db/test.sqlite3

production:
  adapter:  postgresql
  encoding: unicode
  pool:     <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  database: <APPNAME>_production
  username: <APPNAME>
  password: <%= ENV['<APPNAME>_DATABASE_PASSWORD'] %>

Declare Ruby Version

Modify Gemfile

ruby '2.6.5' # your version

Update Essential Phone ph-1 to LineageOS 18.1

Regular 🍟 — Mon, 19 Apr 2021 14:25:17 +0000

Time: 2021-04-03 23:44

Author: vonhyou

In this article, we will install LineageOS 18.1 (Android 11) on Essential Phone ph-1(mata)

Preparation

Download Android SDK Platform Tools for your system.
Unlock the bootloader

$ adb reboot bootloader
$ fastboot devices
$ fastboot flashing unlock

Download recovery, system

Official Website: download.lineageos.org/mata

Download Gapps and Magisk(Optional)

Mind the Gapps: Official website

Magisk: Official website Github

Flash Recovery

$ adb devices
$ adb reboot bootloader
$ fastboot devices
$ fastboot getvar current-slot
# Remember the current slot for next step
$ fastboot flash boot_SLOT <filename>.img
# If the current slot is _a, you should use boot_a

Error: fastboot: error: Couldn't parse partition size '0x'

If this error occurred, you should use command below

$ fastboot flash:raw boot_SLOT <filename>.img

and then next:

$ fastboot set_active other

Reboot to recovery.

Sideload LineageOS

Tap Factory Reset, then Format data / factory reset and continue with the formatting process. This will remove encryption and delete all files stored in the internal storage, as well as format your cache partition.
Select “Apply Update”, then “Apply from ADB” to begin sideload.
Sideload

$ adb sideload <filename>.zip

If the process succeeds the output will stop at 47% and report adb: failed to read command: Success

Sideload Other packs

Reboot to make sure your system is installed correctly
Reboot to recovery mode
Sideload packs like before

$ adb sideload <mindthegapps>.zip
$ adb sideload <magisk>.zip

Error: Zip Signature Verification failed

Just ignore it.

References

Install LineageOS on mata. wiki.lineageos.org
Mata readthedocs. mata.readthedocs.io
XDA Guide. How to Install TWRP & Root Essential PH-1(Method 2)

Remove .DS_Store File from Git Repo

Regular 🍟 — Mon, 19 Apr 2021 13:43:36 +0000

Time: 2021-03-31 08:43 UTC+8:00

Author: vonhyou

.DS_Store is a file that stores custom attributes of its folder (like icons). .DS_Store is a abbr. of Desktop Service Store . This file is similar to the desktop.ini in Windows OS. So that, it's not necessay to add this file into a git repo. Let me tell you how to remove it by adding .gitignore rules.

If you had already add .DS_Store files into a git repo, you have to delete it using command below:

$ find . -name .DS_Store -print0 | xargs -0 git rm -f --ignore-unmatch

Append a rule to .gitignore file

$ echo .DS_Store >> .gitignore

Update repo

$ git commit -am "remove .DS_Store files"

If you don't want to repeat it, it's possible to set this rule globally.

Creat a new file called .gitignore_global (or any other you like )

$ touch ~/.gitignore_global

Assign this file as a global rule set

$ git config --global core.excludesfile ~/.gitignore_global

Add the rule to .gitignore_global

$ echo .DS_Store >> ~/.gitignore_global

Done.

`cannot load such file -- rexml/document`

Regular 🍟 — Mon, 19 Apr 2021 13:39:24 +0000

Time: 2021-03-29 22:04 UTC+8:00

Author: vonhyou

Cause

rexml gem is a bundled gem since Ruby 3.0.0. So we must add rexml to Gemfile.

On Ruby 2.6 and 2.7, rexml gem is default gem. So default rexml is used if Gemfile does not include rexml. On these versions of ruby, we must add rexml to Gemfile only if we want to use specific rexml version.

Solution

gem 'rexml', '~> 3.2', '>= 3.2.4'

Add the code above to Gemfile

Full log

/Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:34:in `require': cannot load such file -- rexml/document (LoadError)
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `block in require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:299:in `load_dependency'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/selenium-webdriver-3.142.7/lib/selenium/webdriver/firefox.rb:22:in `<main>'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `block in require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:299:in `load_dependency'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/webdrivers-4.6.0/lib/webdrivers/geckodriver.rb:72:in `<main>'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `block in require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:299:in `load_dependency'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/activesupport-6.1.3/lib/active_support/dependencies.rb:332:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/webdrivers-4.6.0/lib/webdrivers.rb:4:in `<main>'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler/runtime.rb:66:in `block (2 levels) in require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler/runtime.rb:61:in `each'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler/runtime.rb:61:in `block in require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler/runtime.rb:50:in `each'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler/runtime.rb:50:in `require'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/bundler-2.2.14/lib/bundler.rb:173:in `require'
        from /Users/toreality/RubymineProjects/sample_app/config/application.rb:7:in `<top (required)>'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:92:in `require'                      
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:92:in `preload'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:157:in `serve'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:145:in `block in run'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:139:in `loop'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application.rb:139:in `run'
        from /Users/toreality/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/spring-2.1.1/lib/spring/application/boot.rb:19:in `<top (required)>'
        from <internal:/Users/toreality/.rbenv/versions/3.0.0/lib/ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
        from <internal:/Users/toreality/.rbenv/versions/3.0.0/lib/ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
        from -e:1:in `<main>'

Migrate My Blog to dev.to

Regular 🍟 — Mon, 19 Apr 2021 13:36:27 +0000

After wandering between different blog solutions, I tend to look for a stable platform to ensure that I am actually writing articles instead of writing blog framework or something.

About a month ago, I made a beautiful(maybe) prototype of my dream blog, and plan to implement it by Rails in six months. But the development process killed my interest, and made me realize how great a full-stack engineer really is.

Fortunately I learned a lot during the development process and accumulated a lot of articles, not just focus on Rails or ruby. Although some of the articles doesn't fit well on dev.to -- a platform where developers gather, I still want to use it to archive my words (I'll make sure that they'll not violate community rules)

As for that project (toreality), I choose to forget about it for the time being and wait until I have enough time and knowledge before making a decision.

The last word:

puts 'hello, dev.to!'

DEV Community: Regular 🍟

Prime Sieve Algorithm Cheat Sheet

Sieve of Eratosthenes

Sieve of Euler

*Sieve of Sundaram

Add a DM Button to Your Tweet

What the Twitter DM Button is?

How I Started

How it Ended

Accurately Judge Data Types by Using Regex

Integers

Floats

Regex for Verifying Email Address

My Minimal Lisp Interpreter

Try Scheme Lisp

Install mit-scheme on macOS

Run Interpreter in Terminal

Use Scheme Lisp as a Calculator

Try cons and list

Define and Let

Condition

Implement and Release of My Lisp

Preparations: Design

Keywards of My Lisp

Operator of My Lisp

Build-in Methods of My Lisp

Parse

Global env

Eval

REPL

Usage

"Feature" of Prol

References

A Better Way to Deploy Rails app on Heroku

Force SSL

Switch to Puma

Declare Ruby Version

Update Essential Phone ph-1 to LineageOS 18.1

Preparation

Flash Recovery

Sideload LineageOS

Sideload Other packs

References

Remove .DS_Store File from Git Repo

`cannot load such file -- rexml/document`

Cause

Solution

Full log

Migrate My Blog to dev.to

Install `mit-scheme` on macOS

"Feature" of `Prol`