Julia

This page is derived in large part from the : Think Julia Book. Get new packages at: Julia Observer.

Julia Academy
Github: Foundations of Machine Learning

 Keywords
 abstract type  baremodule  begin    break   catch
 const          continue    do       else    elseif
 end            export      finally  for     false
 function       global      if       import  in
 let            local       macro    module  mutable struct
 primitive type quote       return   true    try
 using          struct      where    while

Operators

isa

n isa Int64

Values and Types

nothing

  typeof(nothing) --> Nothing

Formal and Natural Languages
Variables, Expressions and Statements

Variable names can be as long as you like. They can contain almost all Unicode characters, but they can’t begin with a number.
typing unicode: \:turtle: TAB, \pi TAB , if you press tab twice you get suggestions
The subscript numbers are available in the Unicode character encoding \_1 TAB, \_2 TAB, etc. .
Superscript numbers are also available ;{ ^2 TAB

Assignment Statements

Variable Names

Expressions and Statements

An expression is a combination of one or more values, variables and operators. A statement is a unit of code that has an effect.

Operator Precedence

String Operations

 string1 * string2,  for string concatenation
 string^x concat x repetions of string

Comments

 # for comments

Functions

Converstion

parse(Int64, "10")
parst(Float64, "2.71")

trunc(Int64, 3.3333)

Math Functions

log10()
sqrt()
exp(1.0)
abs()

Defining New Functions

function myNewFunction(arg)
    x = "hello "
    println(x * arg * " hello")
end

Useful Functions

time()
show()

Turtles

Packages can be installed in the REPL by entering the Pkg REPL-mode using the key ].

(v1.0) pkg> add https://github.com/BenLauwens/ThinkJulia.jl

Before we can use the functions in a module, we have to import it with an using statement:

julia> using ThinkJulia

Docstring

"""
polyline(t, n, len, angle)

Draws n line segments with the given length and
angle (in degrees) between them.  t is a turtle.
"""
function myfunc()
end

then type ?

help?> myfunc

Conditionals and Recursion

Floor Division and Modulus

÷ (div TAB)

Boolean Expressions

      typeof(true)         # Bool
      x == x               # x is equal to x
      x != y               # x is not equal to y
      x ≠ y                # (ne TAB)
      x > y                # x is greater than y
      x < y                # x is less than y
      x >= y               # x is greater than or equal to y
      x ≥ y                # (ge TAB)
      x <= y               # x is less than or equal to y
      x ≤ y                # (le TAB)

Logical Operators

&& , || , and ! .

Conditional Execution

if x < y
    println("x is less than y")
elseif x > y
    println("x is greater than y")
else
    println("x and y are equal")
end

if 0 < x < 10
    println("x is a positive single-digit number.")
end

Keyboard Input

text = readline()

Fruitful Functions

Return Values

Incremental Development

Composition

Boolean Functions

More Recursion

Leap of Faith

One More Example

Checking Types

Iteration

Reassignment

Updating Variables

The while Statement

break

continue

Square Roots

Algorithms

Strings

Characters

A String Is a Sequence

length

Traversal

String Slices

Strings Are Immutable

String Interpolation

Searching

Looping and Counting

String Library

The ∈ Operator

String Comparison

Case Study: Word Play

Reading Word Lists

Looping with Indices

Arrays

An Array is a Sequence

Arrays Are Mutable

Traversing an Array

Array Slices

Array Library

Map, Filter and Reduce

Dot Syntax

Deleting (Inserting) Elements

Arrays and Strings

Objects and Values

Aliasing

Array Arguments

Dictionaries

A Dictionary Is a Mapping

Dictionary as a Collection of Counters

Looping and Dictionaries

Reverse Lookup

Dictionaries and Arrays

Memos

Global Variables

Tuples

Tuples Are Immutable

Tuple Assignment

Tuples as Return Values

Variable-length Argument Tuples

Arrays and Tuples

Dictionaries and Tuples

Sequences of Sequences

Case Study: Data Structure Selection

Word Frequency Analysis

Random Numbers

Word Histogram

Most Common Words

Optional Parameters

Dictionary Subtraction

Random Words

Markov Analysis

Data Structures

Files

Persistence

Reading and Writing

Formatting

Filenames and Paths

Catching Exceptions

Databases

Serialization

Command Objects

Modules

Debugging

Structs and Objects

Composite Types

Structs are Immutable

Mutable Structs

Rectangles

Instances as Arguments

Instances as Return Values

Structs and Functions

Time

Pure Functions

Modifiers

Prototyping Versus Planning

Multiple Dispatch

Type Declarations

Methods

Additional Examples

Constructors

show

Operator Overloading

Multiple Dispatch

Generic Programming

Interface and Implementation

18. Subtyping

Cards

Global Variables

Comparing Cards

Unit Testing

Decks

Add, Remove, Shuffle and Sort

Abstract Types and Subtyping

Abstract Types and Functions

Type Diagrams

Debugging

Data Encapsulation

The Goodies: Syntax

Named Tuples

Functions

Blocks

Control Flow

Types

Methods

Constructors

Conversion and Promotion

Metaprogramming

Missing Values

Calling C and Fortran Code

The Goodies: Base and Standard Library

Measuring Performance

Collections and Data Structures

Mathematics

Strings

Arrays

Interfaces

Interactive Utilities

Debugging

error()

Syntax Errors
Runtime Errors
Semantic Errors

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28aug21

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