Syntax bestiary

bestiary.md

Simple value literals

Numbers

syntax	examples	languages
decimal literals	-123.45	(most languages)
scientific notation	1.23e-2
prefix hexadecimal	0xDEADBEEF
prefix binary	0b1110
prefix octal	0o777
unix-style octal	0777	C, JS (deprecated)
radix prefix	16rDEADBEEF	Smalltalk

Strings

syntax	examples	languages
single quote	'a string'	JS, Python, Ruby, Smalltalk
double quote	"a string"	JS, Python, Ruby*, Swift, Rust, Elixir*, Clojure
backtick	`a string`	JS*
sigils	%q(foo bar baz)	Ruby
...	%Q(foo bar baz)	Ruby*
...	~s(foo bar baz)	Elixir*

* - Allows interpolation

Interpolation

syntax	examples	languages
sigil only	$value	PHP, Dart
escaped expr	${value}	JS, PHP, Dart
...	#{value}	Ruby
...	$(value)	Julia
...	\(value)	Swift

Multiline strings

syntax	examples	languages
backticks	` line 1 line 2 `	JS*
EOL backslash	"line 1 \ line 2"	JS
triple quotes	""" line 1 line 2 """	Python*, Elixir*
heredoc	<<HEREDOC line 1 line 2 HEREDOC	Ruby*
implicit concatenation	"line 1" "line 2"	C, Python

* - Preserves newlines

Chars

syntax	examples	languages
single quote	'A'	Rust
question mark	?A	Elixir
backslash	\A	Clojure

Regular expressions

syntax	examples	languages
Perl-style	/foo.+b[ar]$/	JS, Ruby
tagged string	r"foo.+b[ar]$"	Python, Julia
...	#"foo.+b[ar]$"	Clojure
sigil	~r/foo.+b[ar]$/	Elixir

Interned strings (symbols, keywords, etc)

syntax	examples	languages
colon	:foo	Ruby, Clojure, Elixir, Julia
single quote	'foo	Scheme, Clojure*, Scala

Other stringlike values

syntax	examples	languages	notes
char list	'a list of chars'	Elixir	linked list of chars used for backwards compatibility with older Erlang code

Composite value literals

	homogeneous	heterogeneous
by order	List	Tuple
by name	Dictionary	Record

Tuples

syntax	examples	languages
parens	(foo, bar)	Elm, Python*, Julia, Rust, Swift
curly	{foo, bar}	Elixir
multiple return, but no tuple value type	return (foo, bar)	Go*
idiomatically uses lists	[foo, bar]	JS, Clojure, PHP, Ruby*

* - parens/brackets optional

Lists

alt. "vectors", "arrays"

syntax	examples	languages
brackets	[1, 2, 3]	JS, Ruby, Python, Elixir, Elm, Clojure*, PHP†
braces	{1, 2, 3}	Lua†, Java, C
tagged braces	[]int{1, 2, 3}	Go
macro	vec![1, 2, 3]	Rust

* - commas optional † - syntactic sugar for dictionary with integer keys

access by index

syntax	examples	languages
subscript	x[1]	(most languages)

slices

syntax	examples	languages
colon range	x[start:end]	Python, Go
subscript with range object	x[start..end]	Ruby

cons-truction

syntax	examples	languages
cons operator	first :: second :: rest	Elm
wrapped cons	[first, second | rest]	Elixir
spread	[first, second, ...rest]	JS
...	[first, second, *rest]	Ruby, Python

NOTE: 'spread' can go anywhere in list; 'wrapped cons' can only go in last position

Other listlike literals

syntax	examples	languages	notes
quoted sexpr	'(foo bar)	Clojure	used for representing syntax, not (normal) data
set	#{ 1 2 3 }	Clojure
set with type hint	var x : Set = [1,2,3]	Swift
array (not linked list)	[| 1, 2, 3 |]	Reason, OCaml	contiguous memory, O(1) lookup
byte array	<<1, 2, 3>>	Elixir	contiguous memory, O(1) lookup, bytes only
matrix	[1 2; 3 4]	Julia	multidimensional array

Records

alt. structs

syntax	examples	languages
tagged	Point{ x: 123, y: 456 }	Rust, Go
positional	point p = { 123, 456 }	C
designated initializer	{ .x = 123, .y = 456 }	C
extensible records	{ x = 123, y = 456 }	Elm
constructor function	Point(x: 123, y: 456)	Swift, Ruby
idiomatically uses dicts		JS, Python, Clojure, Elixir

static field access

syntax	examples	languages
dots	point.x	C, Go, Rust, Swift, JS, Ruby, Elm, Elixir
dict lookup only		Python, Clojure

Dictionaries

alt. map, hash, associative array, table

syntax	examples	languages
braces	{"x": 123, "y": 456}	JS, Python
braces + bare	{x: 123, y: 456}	JS, Ruby
braces + equals	{x=123, y=456}	Lua
braces + arrow	{:x => 123, :y => 456}	Ruby
...	%{:x => 123, :y => 456}	Elixir
braces + alternate kv	{:x 123 :y 456}	Clojure
square + arrow	["x" => 123, "y" => 456]	PHP
square + colon	["x": 123, "y": 456]	Swift

access by key

syntax	examples	languages
subscript	x[key]	JS, Python, Ruby, Lua, Elixir, PHP, Swift

spread

syntax	examples	languages
same as list	{ ...rest }	JS
double-splat	{ **rest }	Ruby, Python

Other key-value structures

Elixir keyword lists

[x: 123, y: 456] = [{:x, 123}, {:y, 456}] lookup is O(n)

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Typed structures (e.g. classes, enums, variants)

Functions & Blocks

Operators

Patterns & assignment

Modules

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