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Data Types Mapping

[ToC]

Overview

The Hamler Data Types are mapping to Erlang Data types at compile-time. The following table shows the overview of the mappings:

Hamler Data Type Erlang Data Type Mapping Description
Atom(Symbol in Ruby) atom()
Bool boolean() true -> true
false -> false
Char char()
Integer(Int) integer() Integer type
Float(Double) float() Float type
String string()
Tuple tuple()
List list()
Map map()
Record map()
Binary binary() | bitstring()
Port port() Erlang Port
Pid pid() Erlang Pid
Reference(Ref) reference() Erlang Reference

Atoms Mapping

Atom is a constant with name, which is also known as Symbol in other languages, such as Ruby.

Atoms in Hamler are imported from Erlang, defined as a primitive type, but have a different syntax from Erlang.

Atoms in Hamler start with a colon :

:ok
:error
:the_1st_Atom
atom("node@127.0.0.1")

Atoms in Erlang:

ok
error
the_1st_Atom
'node@127.0.0.1'

Booleans Mapping

The syntax of Booleans in Hamler is the same as Erlang. The difference is that Boolean is a primitive type in Hamler, while true and false are atoms in Erlang.

Booleans in Hamler:

true
false

Booleans in Erlang:

true
false

Chars Mapping

Chars in Hamler are also UTF-8 Unicode characters but with different syntax from Erlang.

Chars in Hamler are enclosed in single quotes, which is similar to most programming languages.

'a'
'b'
'の'

Chars in Erlang start with '$':

$a
$b
$の

Integers Mapping

Integers in Hamler are the same as Erlang, with unlimited size. Hamler defines Int as an alias for Integer.

Binary, octal, and hex integers in Hamler have a different syntax than Erlang.

Integers in Hamler:

1, 2, -10
-- binary
0b101, 0B101
-- octal
0o1, 0O1, 0o52, 0O752
-- hex
0x1, 0X1, 0x2a, 0X2A, 0xff

Integers in Erlang:

1, 2, -10
-- binary
2#101, 2#10
-- octal
8#1, 8#52, 8#752
-- hex
16#01, 16#2a, 16#2A, 16#ff

Floats Mapping

Floats in Hamler are the same as Erlang, which are also known as Doubles in other languages.

Floats in Hamler and Erlang:

1.0, 1.0e10
2.3
2.3e-3
0.0023

Strings Mapping

Strings in both Hamler and Erlang are a list of UTF-8 characters.

Strings in Hamler and Erlang:

"Hello, World!"
"你好，世界"
"ハロー、ワールド"

Tuples Mapping

Tuples are defined as primitive data types in Hamler and compiled to Erlang tuples.

The differences from Erlang are as below:

  • Tuples in Hamler are enclosed within parentheses, while Tuples in Erlang are enclosed in braces.

  • The maximum length of Tuples in Hamler is 7, while there is no limit in Erlang.

Tuples in Hamler:

(1, "a", true)
(1, "a")
(:error, "Reason")

-- fst, snd
fst (1, 'a') :: Integer -- 1
snd (1, 'a') :: Char    -- 'a'

Tuples in Erlang:

{1, "a", true}
{1, "a"}

{error, "Reason"}

Lists Mapping

Lists in Hamler are the same as in Erlang.

Lists in Hamler:

{-- List --}
[] -- empty list
[1,2,3] -- Integer list

[1|[2,3]] -- Cons
[1|[2|[3|[]]]] -- Cons

[x|_] = [1,2,3]  -- List pattern
[_|xs] = [1,2,3] -- List pattern
[x|xs] -- Cons

Lists in Erlang:

%% List
[]      %% empty list
[1,2,3] %% Integer list

[1|[2,3]]      %% Cons
[1|[2|[3|[]]]] %% Cons

[H|_] = [1,2,3] %% List pattern
[_|T] = [1,2,3] %% List pattern
[H|T]           %% Cons

Enum, Range

Hamler provides an enumeration or range syntax to help construct lists.

[1..10] --[1,2,3,4,5,6,7,8,9,10]

[0, 5..100] -- [0,5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,95,100]

['a'..'z'] --"abcdefghijklmnopqrstuvwxyz"

Maps Mapping

The syntax of Maps in Hamler is the same as Erlang. The differences are listed below:

  • The keys of a Map must have the same type in Hamler;
  • The values of a Map must have the same type in Hamler;
  • The syntax #{k := v} is only used for map pattern matching.

Maps in Hamler:

-- New map, values and keys must have the same type.
m = #{:foo => "foo", :bar => "bar"}

-- Pattern matching
#{:foo := a, :bar := b} = m
a :: String -- "foo"
b :: String -- "bar"

Maps in Erlang:

%% Create a map
M = #{foo => "foo", bar => "bar"}

%% Pattern matching
#{foo := A, bar := B} = M.
A  %% "foo"
B  %% "bar"

Records Mapping

Records in Hamler are mapping to Erlang Maps at compile-time.

Records in Hamler:

type Person = {name :: String, age :: Integer}
john = {name = "John", age = 12}

Compiled to Erlang's Maps:

%% john
#{age => 12,name => "John"}

Binaries Mapping

Binaries in Hamler are imported from Erlang. The Bit Syntax Expressions in Erlang are defined as below:

<<>>
<<E1,...,En>>
          
Ei ::= Value 
     | Value ":" Size 
     | Value "/" TypeSpecifierList 
     | Value ":" Size "/" TypeSpecifierList

The Bit Syntax in Hamler is a bit different from Erlang, that '/' is replaced with ':':

<<>>
<<E1,...,En>>
Ei ::= Value 
    |  Value ":" Size 
    |  Value ":" TypeSpecifierList 
    |  Value ":" Size ":" TypeSpecifierList

Binaries in Hamler:

<<127,0,0,1>>
<<"ABC">>

-- Binary Pattern Match
<<bigI:16:Big-Unsigned-Integer>> = <<1,2>>
<<litI:16:Little-Signed-Integer>> = <<1,2>>

Binaries in Erlang:

<<127,0,0,1>>
<<"ABC">>
<<1:16,2:4,3:4>>

-- Binary Pattern Match
<<X:3,Y:5,Z:8>> = <<1,0>>
<<BigI:16/big-unsigned-integer>> = <<1,2>>
<<LitI:16/little-signed-integer>> = <<1,2>>

Ports Mapping

The Port data type in Hamler is foreign imported from Erlang.

Pids Mapping

The Pid data type in Hamler is foreign imported from Erlang. Pid in Erlang is a unique identifier of the Erlang lightweight process.

References Mapping

The Reference data type in Hamler is a foreign imported data type from Erlang.

Create a Reference in Hamler:

import Data.Ref
makeRef

User-defined data types Mapping

The constructors of Sum/Product algebraic data types are mapping to tuples in Erlang at compile-time.

Hamler:

-- Sum datatype
data Color = Red | Green | Blue
Red   -- {'Red'}
Green -- {'Green'}
Blue  -- {'Blue'}

-- Product datatype
data Pair = Pair Integer Integer
Pair 3 4 -- {'Pair',3,4}

-- Maybe
data Maybe a = Just a | Nothing
Nothing -- {'Nothing'}
Just 5  -- {'Just',5}

Erlang:

{'Red'}   %% Red
{'Green'} %% Green
{'Blue'}  %% Blue

{'Pair',3,4} %% Pair 3 4

{'Nothing'} %% Nothing
{'Just',5}  %% Just 5