首页 > itarticle > elixir guides 02

elixir guides 02

admin 11月 12, 2020 0

Basic arithmetic

iex> 1 + 2
3
iex> 5 * 5
25
iex> 10 / 2
5.0

iex> div(10, 2)
5
iex> div 10, 2
5
iex> rem 10, 3
1

Elixir also supports shortcut notations for entering binary, octal, and hexadecimal numbers:

iex> 0b1010
10
iex> 0o777
511
iex> 0x1F
31

Scientific notation:

iex> 1.0
1.0
iex> 1.0e-10
1.0e-10
 

iex> round(3.58)
4
iex> trunc(3.58)
3

Booleans

Elixir supports true and false as booleans:

iex> true
true
iex> true == false
false

Elixir provides a bunch of predicate functions to check for a value type:

  • is_boolean/1
  • is_integer/1
  • is_float/1
  • is_number/1

The h helper can also be used to access documentation for any function. For example h is_integer/1 or h ==/1.

Atom

An atom is a constant whose name is its own value. Some other languages call these symbols:

iex> :hello
:hello
iex> :hello == :world
false

The booleans true and false are, in fact, atoms:

iex> true == :true
true
iex> is_atom(false)
true
iex> is_boolean(:false)
true

Finally, Elixir has a construct called aliases which we will explore later. Aliases start in upper case are also atoms:

iex> is_atom(Hello)
true

String

Strings in Elixir are delimited by double quotes, and they are encoded in UTF-8:

iex> "hellö"
"hellö"

We can print a string using the IO.puts/1:

iex> IO.puts "hellonworld"
hello
world
:ok

Anonymous functions

iex> add = fn a, b -> a + b end

iex> add.(1, 2)
3
iex> is_function(add)
true
iex> is_function(add, 2) # check if add is a function that expects exactly 2 arguments
true
iex> is_function(add, 1) # check if add is a function that expects exactly 1 argument
false

iex> double = fn a -> add.(a, a) end
#Function<6.71889879/1 in :erl_eval.expr/5>
iex> double.(2)
4

iex> x = 42
42
iex> (fn -> x = 0 end).()
0
iex> x
42

(Linked)Lists

List operators never modify the existing list:

iex> [1, 2, true, 3]
[1, 2, true, 3]
iex> length [1, 2, 3]
3

iex> [1, 2, 3] ++ [4, 5, 6]
[1, 2, 3, 4, 5, 6]
iex> [1, true, 2, false, 3, true] -- [true, false]
[1, 2, 3, true]

The functions hd/1 and tl/1:

iex> list = [1, 2, 3]
iex> hd(list)
1
iex> tl(list)
[2, 3]

Tuples

iex> {:ok, "hello"}
{:ok, "hello"}
iex> tuple_size {:ok, "hello"}
2

iex> tuple = {:ok, "hello"}
{:ok, "hello"}
iex> elem(tuple, 1)
"hello"
iex> tuple_size(tuple)
2

iex> tuple = {:ok, "hello"}
{:ok, "hello"}
iex> put_elem(tuple, 1, "world")
{:ok, "world"}
iex> tuple
{:ok, "hello"}

Basic Operators

++, --, <>:

iex> [1, 2, 3] ++ [4, 5, 6]
[1, 2, 3, 4, 5, 6]
iex> [1, 2, 3] -- [2]
[1, 3]

iex> "foo" <> "bar"
"foobar"

or,and,not
||,&&,!
==,!=,===,!==,<=,>=,<,>

Note: If you are an Erlang developer, and and or in Elixir actually map to the andalso and orelse operators in Erlang.

iex> true and true
true
iex> false or is_atom(:example)
true

iex> 1 and true
** (BadBooleanError) expected a boolean on left-side of "and", got: 1

iex> false and raise("This error will never be raised")
false
iex> true or raise("This error will never be raised")
true

# or
iex> 1 || true
1
iex> false || 11
11

# and
iex> nil && 13
nil
iex> true && 17
17

# !
iex> !true
false
iex> !1
false
iex> !nil
true


iex> 1 == 1
true
iex> 1 != 2
true
iex> 1 < 2
true


iex> 1 == 1.0
true
iex> 1 === 1.0
false

iex> 1 < :atom
true

number < atom < reference < function < port < pid < tuple < map < list < bitstring

微海报分享

近期文章

近期评论

标签

热门

文章归档

分类目录

功能