Slang

Example code

# this is a comment
#| and that is a
	multiline one. |#

const u32 n = 123123  # n is of type const u32
const i64 m = 10**18  # m is of type const i64
const int z = 2**128  # z is of type const int (unsized)
const auto q = 2**256  # q is of type const int

char f(str x) {  # f() is of type char, x is of type str
	auto c = x[1]  # c is of type char
	return c
}

char g(str x) {  # g() is of type char, x is of type str
	return x[0]  # retval is of type char
}

int h(int x) = x+1  # h() is of type int, x is of type int

void main() {
	print(h(n), \
		f('123asd') + g('32') + 1)  #--> «123124 f»
	print(q/z/2**96)  #--> «4294967296.0»
}

main()

Tokens

• Keywords
• Identifiers
• Literals
• Operators
• Specials

Token resolution order

1. Special
2. Operator
3. Literal
4. Keyword
5. Identifier

Syntax structures

Note: * after syntax unit means any number of them.

Abstract

• {[<\n | ;>]* <<expr> <\n | ;>>* [<\n | ;>]*} — code
• <<expr> | <code>> — block

Primitive

• <<literal> | <funccall> | <attrget> | <itemget> | <identifier> | <lambda>> — value
• <value>\[<value>\] — itemget
• <(<expr>) | <value> | <operator> <expr> | <expr> <operator> <expr>> — expr (f(x+3) is an instance of expr, also f, x+3 and x are exprs too)

Non-final

• [modifier]* <type> — typedef (left-hand type definition)
• [typedef] <identifier> [? | + | * | ** | =<expr>] — argdef (argument definition)

? — if present then argument value, none else.
+ — tuple with at least one argument.
* — tuple with any number of arguments.
** — object with keyword arguments.
= — default value if argument not specified.

• ([<argdef>[, <argdef>]*]) -> <typedef> = <expr> — lambda (lambda function)
• <<expr>[, <expr>]*[, *<expr>] | *<expr>> — callargs
• <<identifier>=<expr>[, <identifier>=<expr>]*[, **<expr>] | **<expr>> — callkwargs

Final (ordered by resolution order)

• <typedef> <identifier>([<argdef>[, <argdef>]*]) <<code> | = <expr>> — funcdef (function definition)
• <exprkeyword> [expr] — keywordexpr (keyword expression)
• <typedef> <identifier> [= <value>] — vardef (variable definition)
• <identifier> = <value> — assignment
• <value>([<callargs> | <callkwargs> | <callargs>, <callkwargs>]) — funccall (function call)
• <expr> — expr evaluation (only in REPL)
• if (<expr>) <block> — conditional
• for (<identifier> in <expr>) <block> — forloop
• while (<expr>) <block> — whileloop
• else <block> — elseclause

Keywords

• return [expr] — return from function

Modifiers

• const — immutable/constant variable

Reserved keywords

• def

Identifiers

Non-empty sequence of alphanumeric characters plus underscore («_»), not starting with a digit character.

Regex: [_\w]+[_\w\d]*

Data types

• i8, i16, i32, i64, i128 — fixed size integer

• u8, u16, u32, u64, u128 — fixed size unsigned integer

• f8, f16, f32, f64, f128 — fixed size IEEE-754 floating point number

• uf8, uf16, uf32, uf64, uf128 — fixed size unsigned floating point number

• int — unsized («big») integer

• uint — unsized unsigned integer

• float — unsized floating point number

• ufloat — unsized unsigned floating point

• bool — logical (boolean) value

• byte — single byte

• char — UTF-8 character

• str — UTF-8 string

• void — nothing (or anything...)

• auto — compile-time type deduction based on value

Literals

Note: * after syntax unit here means any number of them, + means at least one.

• <<0<b | o | x>><digit+> | <digit+>.<digit*> | <digit*>.<digit+>> — number
• <"<character*>" | '<character*>'> — string

Operators

• <operator> <operand> — unary operators usage
• <operand> <operator> <operand> — binary operators usage
• <operand> <operator>= <operand> — in-place operator usage

Character operators

A set of pre-defined character operators:

• !$%&*+-:^~ — unary charset
• %&*+-/<=>^| — binary charset
• ==, **, //, <<, >> — double-char binary operators

Keyword operators

A set of pre-defined keyword operators:

• not — unary keyword operator
• and, or, xor, is, is not, to — binary keyword operators

Specials

• #, #|, |# — comment specials
• ; — expr separator special
• ->, @., @, ., : — attrget optype specials
• [, ] — itemget specials
• \,?=(){} — other specials charset

Footnotes

All character class checks are performed in current locale.

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by Sdore, 2019