Julia

use latex symbol

type \… and tab

built-in

constant

π or pi = 3.1415926535897... Inf and NaN im

math function

sqrt()

variable

check type

typeof()

numerical type

extreme representable value

typemin(Type1) / typemax(Type1)

convert to bits bitstring()

avoid overflow using big()

create BigInt or BigFloat or use big"…" if the number if too big for Int or Float

machine epsilon eps(Type1)

implicit numeric multiplication

2x^2x is equivalent to 2 * x^(2 * x)

arithmetic operation

  • ÷ integer division
  • ^ power
  • . make the next operator element-wise
    e.g. .+ element-wise add

numeric comparison

Julia support real Unicode operator

  • isequal() compare object
  • isfinite()
  • isinf()
  • isnan()

Julia support arbitrary comparison chaining

conversion Type1(…)

pattern matching

_ can be assigned value

string

Use double or triple quote for string literal

index take raw bytes

index start at 1

can use begin and end for index

  • r"…" regex string
  • b"…" byte string
  • v"…" version literal
  • raw"…" raw string

string concatenation

string(str1, str2, …) combine multiple string

str1 * str2 concatenate them

"$str1 and $(str2)." formatted string

tuple and list

  • (a, b, c) tuple
  • [a, b, c] list

match tuple or list or variable length

first, second, rest... = (a, b, c, d, e)
# rest = (c, d, e)

function

traditional syntax

function func1(args)
    # …
end

assignment form

func1(args) = # …
  • the last expression is returned
  • nothing is returned without a return value

function argument type annotation

func1(arg1::Type1, …)

optional argument

func1(arg1, opt_arg1=default_val1, …)

  • optional argument are positional

keyword argument

func1(arg1, ¬; keyword_arg1=default_val1, …)

  • keyword argument must have the keyword specified when called
  • keyword argument does not need a default value, but then it will be mandatory
  • keyword name is implied as the variable name if it appear after ; when called

function taking function as argument

func1(f::Function, arg2, …)

  • call with named function

  • use with anonymous function

    func1(x -> …, val2, …)

  • use with do-block

    func1(val2, …) do arg1_for_function_passed_in, …
    # …
end

dispatch

function can have different method for different type

anonymous function

(args…) -> # …

or

function (args)
    # …
end

function composition

(f ∘ g)(args)

is equivalent to

f(g(args))

function chaining (function piping)

args |> g |> f

is equivalent to example above

use piping with broadcasting

.|> apply piping element-wise

vectorize function

func1.(args)

apply func1 to each element in each argument, equivalent to

broadcast(f, args)