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node {
    echo 'No quotes in single backticks'
    sh 'echo $BUILD_NUMBER'
    echo 'Double quotes are silently dropped'
    sh 'echo "$BUILD_NUMBER"'
    echo 'Even escaped with a single backslash they are dropped'
    sh 'echo \"$BUILD_NUMBER\"'
    echo 'Using two backslashes, the quotes are preserved'
    sh 'echo \\"$BUILD_NUMBER\\"'
    echo 'Using three backslashes still results in preserving the single quotes'

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OpenSSL Base64 Encoding: Binary Safe and Portable

Herewith is an example of encoding to and from base64 using OpenSSL's C library. Code presented here is both binary safe, and portable (i.e. it should work on any Posix compliant system e.g. FreeBSD and Linux).

License

The MIT License (MIT)

Copyright (c) 2013 Barry Steyn

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Compile & Linking

1. C compile source file then link object files and include libs to an executable prorgram.
2. Linking phase is runned by ld.exe another program, or as.exe as assembly program.
3. To compile and link a program as a shared library(.dll in windows, .so in Unixes), use -shared.
4. By default compile will inlcude default dependencies, cpp -v to check the list.

g++ -Wall -g -o Hello.exe Hello.cpp

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Why yarn?

The most important factor is shrinkwrap.json may out of date when developer forget to manually npm shrinkwrap to update npm-shrinkwrap.jsonafter upgrading.

https://code.facebook.com/posts/1840075619545360

Env

1. rubyenv
2. ruby-2.4.1

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What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Element

Box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent
• elem.clientLeft, elem.clientTop, elem.clientWidth, elem.clientHeight
• elem.getClientRects(), elem.getBoundingClientRect()

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Why typeclass?

Polymorphism and Decoupling.

Polymorphism

1. Parametric

List of Int, list of Double, types are as type parameters in a context(List), not as types of direct values(without context) which infer the idea of ad-hoc polymorphism

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Traversabel#flatten

If a type class extend or transform to GenTraversableOnce type, then it is flattenable. But you have to write your own GenTraversableOnce rule

import scala.language.implicitConversions
implicit def int2Traversable[T <: Any](n: T): Traversable[Any] = n match {
  case x: List[Any] => x
  case c => Traversable[T](c)
}

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Slick 3.2.0 source code generator prepend final key word for Entity type case class generation, this leads the issue have not been resolved since years:

https://issues.scala-lang.org/browse/SI-4440

The workaround is to create custom source code generator then override that def caseClassFinal = true to false instead.

Related thread:

slick/slick#1665

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package main

import (
	"github.com/graphql-go/graphql"
	"github.com/graphql-go/handler"
	"net/http"
)

type Todo struct {
	ID   string `json:"id"`

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Review of Effective Ruby

Item 2

All Objects Could Be nil

All objects are mutable by default. It can be nil, using nil?, is_a?, to_a, etc. to help the value validaiton for method input.

Item 3