smallest

"Smallest Possible Language" - a self-hosted compiler.

Why!?

For fun. Design considerations:

• Define the smallest possible (high-level) language that can compile itself.
• As simple as possible, but no simpler.
• All keywords and symbols are single-character non-alphanumerics. Some symbols (e.g., >) have been omitted. Just use < instead.
• No strings, structs, floats, bytes, or booleans. Well...strings can be represented as arrays, and booleans can be represented as ints.
• The only data types are ints (32-bits) and arrays of ints.

Keywords (Symbols)

; - comment to end of line

$ - print the (int) argument as a character

# - print the (int) argument as an integer

~ - while

? : - if/else

^ - return

@ - input

_ - define function

% - allocate array

' - character constant (really just an int)

\ - stop/exit

And the usual math: + - * ( ) [ ] & | ! = <

Note: = is used for both assignment and comparison. ! is the "not equals" comparison.

There is no division or modulo or > or >= or <=.

Blocks are separated with parentheses.

Data types

There are two data types: 32-bit ints and arrays of 32-bit ints.

When comparing ints, the result is an int (0 for false, 1 for true.)

Variables

Variables that start with a (case sensitive) are arrays of ints. All other variables are ints.

Only alphabetic characters are allowed in variable names. Variable and function names are case-sensitive.

Variables can be defined outside functions and are then global for all functions to read and modify.

Arrays

Naming

Variables that start with a (case sensitive) are arrays of ints.

Declaration

arr%4

Allocates an array named arr of size 4.

Array sizes can be dynamic:

arr%(i+3)

Allocates an array of size i+3.

Indexing

arr[0] = 34
arr[1] = 65
arr[2] = 34
arr[3] = 0

The following line is equivalent to if arr[i] == 0 { println("Empty") }:

? (arr[i]=0) ( $'E $'m $'p $'t $'y $10 )

Length

There is no "array length" operator.

Functions

Naming

Only alphabetic characters are allowed in function names.

Functions that start with v (case sensitive) are void. Functions that start with a (case sensitive) return an array. All other functions return int.

Declaration & call

Factorial:

_fact(n) ( ; takes an int, returns an int
  ? n < 2 ( ^ n)  ; if n < 2 { return n}
  ^ n * fact(n-1)  ; return n * fact(n-1)
)

Print an array as a string:

_vprint(as) (
  i=0
  ~ (as[i] ! 0) (   ; while as[i] != 0
    $ as[i]       ; print as[i] as a character
    i=i+1
  )
)