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Bytecode

Notes / ideas

I'm not having much of a clue what I'm doing here, it might also be a bit premature to think about the bytecode before the syntax and semantics are clear.

Special type coding for integers? Con: implementation becomes less generic

  • ?? nothing?
  • 00 block
  • 01 function
  • 10 unsigned long int (62-bit)
  • 11 long int (62-bit)

Datatypes / values

2 (3?) basic datatypes

  • Nothing?
  • Block / instance / class / prototype
    • Variable-length code for class?
    • number of elements (size)
    • optionally instance contents
  • Function
    • list of parameters (with names and default values) and return values
    • class

What to do for values of native types (fn.["()"] and number.value)?

  • make them return themself? fn.["()"] == fn and number.value == number?
    • would make sure every value is of "Block" / "Object" basic datatype, no datatype storage needed (saves a couple bits, don't know if necessary)
    • store actual value in some kind of metadata?
  • extra (3rd?) basic type: native/internal blob, storing value?
    • con: possibly extra indirection
  • no number.value, fn.["()"] is other (native) function with ["()"] set to itself, like javascript function.call: fn.["()"].["()"] == fn.["()"]
    • store actual value in some kind of metadata / userdata?

Interpreter / VM

https://craftinginterpreters.com/contents.html

Ideas

  • For functions returning closures, somehow store the returned function inside the outer function to prevent re-creating functions every time

Variables / fields

Some way to not have to allocate for simple ("primitive") types (int, float, bool, nil)

  • modifiers: private, const, static
  • type? possible data duplication, type is also stored in value
  • data or pointer, plus something to indicate which of the two
    • idea: allocate object members directly after object header, relative pointers would improve locality and allow for smaller header size (relative offset can be int or even short, in steps of base size = 2*long?)

Value representation optimisations

8-byte / 64-bit memory layout:

|----7---|----6---|----5---|----4---| |----3---|----2---|----1---|----0---|
 63    56 55    48 47    40 39    32   31    24 23    16 15     8 7      0

. : unused bit          b : boolean
x : any                 f : float distinguisher
p : pointer             s : sign
t : type                e : exponent
i : integer             m : mantissa

Unoptimised value (just a pointer)

Type Layout
pointer pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp

NaN boxing (using signalling NaN because that never occurs normally)

Type Layout
general ffffffff fffffttt xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
float (64 bits) seeeeeee eeeemmmm mmmmmmmm mmmmmmmm mmmmmmmm mmmmmmmm mmmmmmmm mmmmmmmm
pointer .1111111 11110010 pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp
int (50 bits) 01111111 111101ii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii
other (50 bits) 11111111 111101xx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx

Pointer tagging

Type Layout
general xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxttt
float (32 bits) seeeeeee emmmmmmm mmmmmmmm mmmmmmmm ........ ........ ........ .....010
pointer pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp ppppp000
int (63 bits) iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiiii iiiiiii1
other (56 bits) xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxx100

API

Standard library

https://en.wikipedia.org/wiki/Abstract_data_type#Examples

Naming: module / package / library ?

  • module: Lua, Python, ...
  • package: Java, Python, Go, Scala, ...
  • library: Javascript, C, ...

Probably: (inspired by Java/Python, in order from small to large)

  • module: single file
  • package: collection of files (directory/folder)
    • grouping similar functionality
    • needs main file/module
  • collection/bundle: collection of packages
    • packages not necessarily offering similar functionality
    • more about downloading, should be indistinguishable in code?

2 Collections/bundles for language:

  • Base/core/[langname] collection: only essentials, always present / no need to import (for embedding, like Lua)

    • Nil, Bool, Int, Float, ASCIIString, Math/Random, List, ...?

  • Extended collection: more extensive, optional (for stand-alone usage, like Java/Python)

    • ideas: UnicodeString / UTF8String, Debug, OS/IO/FS, Date, Regex, Socket, JSON, encoding/decoding, data structures (Set, Bag, Map, Stack, Queue, ...), Thread, BigInt/BigNum, ...

  • ASCII string and Unicode/UTF8 string separate?

    • maybe Unicode string in base lib, ASCII string in std lib?
      • pro: need unicode support for lexing/parsing anyway so why not provide string
      • con: possibly more resource intensive (string indexing complexity, storage etc)

  • Modulo int type for automatic calculations modulo n, as a generalisation of wrapping int overflow operations

  • Iterator type with default stream-like functions (map, filter, ...)