Lucian's Luscious Lasagna

Constants and functions

Haskell programs are composed of definitions and expressions.

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

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

Haskell uses whitespaces and indentation to specify code boundaries. Code which is part of some expression should be indented further in than the beginning of that expression.

• Module, import, and top-level function definitions must start at the leftmost 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 numbers of spaces.

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

https://en.wikibooks.org/wiki/Haskell/Indentation

Modules

Modules export functions. That means you can use the functions the module makes available in its export statement. A module can also define functions only for internal use. By default, functions that are not explicitly exported cannot be used from outside the module.

At the beginning of a module, we specify the module name. If we have a file called Calculator.hs, then we should name our module Calculator. Then, we specify the functions that it exports and after that, we can start writing the functions. So we'll start with this.

module Calculator ( add ) where

https://learnyouahaskell.github.io/modules#making-our-own-modules

Comments

A comment is some text within the Haskell file that is not interpreted as code. It is mainly intended 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
   spanning multiple lines
-}

Credits

This exercise introduction borrows liberally from Learn You a Haskell for Great Good!, under Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License