Haskell Cheat Sheet printable pdf download

Haskell Cheat Sheet

Strings

– Syntax error; need [-100.. -110] for

negatives.

– Unicode string.

This cheat sheet attempts to lay out the fundamen-

– List from 1 to 100 by

– Single character.

tal elements of the Haskell language and libraries.

2, -1 to 100 by 4.

It should serve as a reference to both those learn-

Multi-line Strings

Normally, it is syntax error if

ing Haskell and those who are familiar with it, but

a string has any actual new line characters. That is,

Lists & Tuples

maybe can’t remember all the varieties of syntax

this is a syntax error:

– Empty list.

and functionality.

– List of three numbers.

It is presented as both an executable Haskell ﬁle

– Alternate way to write lists us-

and a printable document. Load the source into

ing “cons” ( ) and “nil” ( ).

your favorite interpreter to play with code samples

However, backslashes (‘ ’) can be used to “escape”

– List of three characters (strings are lists).

shown.

around the new line:

– List of characters (same

Syntax

– 2-element tuple of a number and a string.

– 4-element tuple of two

Below the most basic syntax for Haskell is given.

The area between the backslashes is ignored. An

functions, a number and a character.

important note is that new lines in the string must

Comments

still be represented explicitly:

“Layout” rule, braces and semi-colons.

A single line comment starts with ‘ ’ and extends

Haskell can be written using braces and semi-

to the end of the line. Multi-line comments start

colons, just like C. However, no one does. Instead,

with ’ ’ and extend to ’ ’. Comments can be

the “layout” rule is used, where spaces represent

That is,

evaluates to:

nested.

scope. The general rule is – always indent. When

Comments above function deﬁnitions should

the compiler complains, indent more.

start with ‘

’ and those next to parameter types

Braces and semi-colons

Semi-colons terminate

While

evaluates to:

with ‘

’ for compatibility with Haddock, a sys-

an expression, and braces represent scope:

tem for documenting Haskell code.

Reserved Words

Function Deﬁnition

Indent the body at least

Numbers

one space from the function name:

The following lists the reserved words deﬁned by

Haskell. It is a syntax error to give a variable or

- Integer

function one of these names.

- Floating point

– List of numbers – 1, 2, ...10

Unless a

clause is present. In that case, in-

– Inﬁnite list of numbers – 100, 101, 102, ...

dent the where clause at least one space from the

– Empty list; ranges only go forwards.

function name and any function bodies at least one

– Negative integers.

space from the

keyword:

c 2008 Justin Bailey.

Haskell Cheat Sheet

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