Basics 1 in

About Basics 1

Constants and functions

Elm programs are composed of definitions and expressions. Everything in Elm is either a definition or an expression.

A constant value is defined with name = expression.

five = 5

six = 3 + 3

Functions are defined with name parameters... = expression, parameters being only separated by space.

add number1 number2 = number1 + number2

Invoking a function also is an expression and is done by specifying its name and passing arguments for each of the function's parameters, separated by space, just like for function definition.

five = add 2 3

Parentheses can be used to specify the order of evaluation of an expression.

six = add 2 (1 * 4)

twelve = add 2 1 * 4

Indentation / significant whitespace

Elm doesn't use syntactic markers such as curly brackets, parentheses, or semicolons to specify code boundaries. It uses whitespaces and indentations instead.

• Module, import, and top-level function definitions must start at the left most column.
• If an expression is split into multiple lines, the code that is part of that expression must be indented under that expression with at least one space.
• Parts of the expression that are grouped together should be indented with equal number of spaces.

-- A function split over multiple lines, so subsequent lines must be indented
add number1 number2 =
    number1 + number2

https://elmprogramming.com/indentation.html

Modules

Each file in Elm is a module, and must contain a module statement before all other code. Module names must match their file name, so module Calculator must be in file Calculator.elm. Anything defined within a module is privately scoped to it and cannot be accessed from outside this module, unless listed in exposing.

-- Define the Calculator module, and expose the `add` function
module Calculator exposing (add)

six = 3 + 3

add number1 number2 = number1 + number2

-- Define the Calculator module, and expose everything within: `six` and `add`
module Calculator exposing (..)

six = 3 + 3

add number1 number2 = number1 + number2

https://elm-lang.org/docs/syntax#modules

Comments

A comment is some text within the Elm file that is not interpreted as code. It is mainly intented to be read by yourself and other programmers. There is a lightweight syntax for single line comments, based on double dashes. Multiline comments are also possible with the {- and -} pair of opening and closing delimiters.

-- a single line comment
-- another single line comment

{- a multiline comment
   spawning multiple lines
-}

Formatting

There is a style guide, and elm-format can be used to automatically format code.