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Review of Confident Ruby

Read API doc

1. any? [{ |obj| block }] → true or false means could either accept 0 or 1 { |obj| block } block.

2. send(symbol [, args...]) → obj means could either accept 0 or many argumetns. if symobol method accept block, then may also appen that block to it, e.g. define_method.

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Xor and Sum

You are given two positive integers a and b in binary representation. You should find the following sum modulo 10 ^ 9 + 7:

Summation(a xor (b shl i)) from i = 0 to 314159

where operation xor means exclusive OR operation, operation shl means binary shift to the left.

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• Item 6

• Ruby find a method by searching its suplerclass until to the top, then back to original class then searching the hierachy for method_missing again.

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// example object

var obj = {'property': 1234}

Object & Prototype

1. Everything is object, except null and undefined.

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Internal of prototype and inheritance(chinese)
https://imazole.wordpress.com/2013/12/23/javascript-prototype-chain/ https://www.byvoid.com/blog/javascript-object-prototype

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Values, variables, and control flow

• _ and $ can be used to name a variable or function as first letter. Digits can not be first letter for naming variable or function.

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Lecture 1

1. Constraint and auto layout.

• Auto Layout Concepts
• The attributes leading and trailing are the same as left and right for left-to-right languages such as English, but in a right-to-left environment such as Hebrew or Arabic, leading and trailing are the same as right and left.
• Constraints are cumulative, and do not override each other. Setting a second width constraint for a view does not remove or alter the first width constraint.

2. @IBOutlet weak var prpoerty.

• Outlets

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Red Black Tree revisit.

	TIME
INSERTION	O(log n)
DELETION	O(log n)
SEARCH	O(log n)

| SPACE | O(n) |

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#Learning CSS Note

###1. Class Selector

If two class selector rules ovelap same properties, the later rule in css file will take it. So it is called css.

If rule selector select element, then more restrictive element will apply that rule. ex: div prior then body.

The precedence is more specific selector will take the higer priority.

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#Weird Part Of JS

1. this is global object if there does not have receiver. If so, it also imply it is a window object, document === window.document.

2. JS engine create this execution context(window object) in bottom of execution stack and run other execution context which is in top of it for you.

3. When you declare a var or define as a function(function expression or function statement), you can find it through window.func() or func() in global environment.

4. Hoisting: var and func are all firstly initialize but not assigned its value yet until the later code assign it. Check code example below.

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#Action Controller Overview

##0. Mass Assignment

1. Mass assignment allows us to set a bunch of attributes at once:

   attrs = {	:first => "John", :last => "Doe", 
   			:email => "john.doe@example.com"}
   user = User.new(attrs)