Typed Tuples proposal

This is follow-on proposal devired from issue#218 in Records & Tuples proposal repository.

Proposal author is Evgeniy Istomin (@MadProbe).

Stage

This proposal is stage 0 in the process document.

Intro

This proposal adds new immutable primitive data structures - typed tuples.

They are similar to existing typed arrays and tuples by concept:

1. There are 11 types of typed tuples.
2. Same as tuples, typed tuples are immutable and primitive.
3. Have same syntax as tuples have.
4. Prototypes of object representations of typed tuples share a prototype - %TypedTuple%
5. %TypedTuple% has same methods as in Typle.prototype and some recent proposals like relative indexing method and array find from last

Syntax

Syntax of typed tuples extends syntax of tuples by adding tokens '<', %TypedTupleTypeNameOrTypeAlias% and '>' between tokens '#' and '['

Examples

var uint32_tuple = #<uint32_t>[0, 1337, 777, 322];
uint32_tuple[0]; // 0
uint32_tuple[3]; // 322
var float64_tuple = #<double>[666, ...uint32_tuple, 42]; // tuples of other types can be "rested" to tuple of another type
function* gen() {
    yield* [0, 1, 2, 3, 4];
}
console.log(#<uint8_t>[...gen()]); // Logs #<uint8_t>[0, 1, 2, 3, 4], any iterator can be used when "resting" into typed tuple
uint32_tuple[0] = 1; // TypeError: Cannot assign to read only property '0' of object '[object Uint32Tuple]'

Syntax Errors

Like in tuples, holes are prevented in syntax.

#<int>[,]; // SyntaxError, holes are disallowed by syntax

Equality

assert(#<int>[0, 1] === #<int>[0, 1]);
assert(#<int>[0, 1] !== #<uint>[0, 1]); // Typed tuples of different types are not equal even if they have same contents
assert(Object(#<int>[0, 1]) !== Object(#<int>[0, 1])); // Object wrappers are different even if they wrap same typed tuple

Typed tuples table

Constructor Name	typeof tuple	Syntax	Aliases
Int8Tuple	"int8-tuple"	#<int8_t>[...values]	char, int8, signed_char
Uint8Tuple	"uint8-tuple"	#<uint8_t>[...values]	byte, uint8, unsigned_char
Uint8ClampedTuple	"uint8-tuple-clamped"	#<uint8_clamped_t>[...values]	byte_clamped, uint8_clamped, unsigned_char_clamped
Int16Tuple	"int16-tuple"	#<int16_t>[...values]	short, int16, char16, char16_t
Uint16Tuple	"uint16-tuple"	#<uint16_t>[...values]	ushort, uint16, uchar16, wchar_t, uchar16_t
Int32Tuple	"int32-tuple"	#<int32_t>[...values]	int, int32, char32, char32_t
Uint32Tuple	"uint32-tuple"	#<uint32_t>[...values]	uint, uint32, uchar32, uchar32_t, codepoint_t
Float32Tuple	"float32-tuple"	#<float32_t>[...values]	float, float32
Float64Tuple	"float64-tuple"	#<float64_t>[...values]	double, float64
BigInt64Tuple	"bigint64-tuple"	#<bigint64_t>[...values]	int64, bigint64, int64_t
BigUint64Tuple	"biguint64-tuple"	#<biguint64_t>[...values]	uint64, biguint64, uint64_t