STABLE is an extremely minimalistic "Forth-like" (but not Forth) language by Sandor Schneider. Originally in C, I have ported it to Typescript to explore what can be done with the one of the world's smallest viable programming languages.
STABLE stands for STAck Bytecode Language & Engine and the original implementation is only about 233 lines of formatted C code and much shorter if all the whitespace is removed.
Go here to see a fully working version of STABLE in your browser.
| opcode | stack effects | description |
|---|---|---|
| + | (a b -- a+b) | addition |
| - | (a b -- a-b) | subtraction |
| * | (a b -- a*b) | multiply |
| / | (a b -- a/b) | division |
| % | (a b -- a%b) | modulo (division remainder) |
| _ | (n -- -n) | negate |
| opcode | stack effects | description |
|---|---|---|
| & | (a b -- a&b) | 32 bits and |
| | | (a b -- a | b) | 32 bits or |
| ~ | (n -- n') | not, all bits invertsed (0=>1 1=>0) |
| opcode | stack effects | description |
|---|---|---|
| # | (a -- a a) | duplicate top of stack |
| \ | (a b -- a) | drop top of stack |
| $ | (a b -- b a) | swap top of stack |
| @ | (a b -- a b a) | (over) copy next of stack on top |
| opcode | stack effects | description |
|---|---|---|
| x | ( -- ) | select register x (x: a..z) |
| ; | ( -- value) | fetch from selected register |
| : | ( value --) | store into selected register |
| ? | ( -- value) | selected register contains an address. Fetch value from there |
| ! | ( value --) | selected register contains an address. Store value there. |
| - | ( -- ) | immediately after register, increment content by 1 |
| * | ( -- ) | immediately after register, decrement content by 1 |
| opcode | stack effects | description |
|---|---|---|
| {X | ( -- ) | start function definition for function X (A..Z) |
| } | ( -- ) | end of function definition |
| X | ( -- ) | call function X (A..Z) |
| opcode | stack effects | description |
|---|---|---|
| . | (value -- ) | display value as decimal number on stdout |
| , | (value -- ) | send value to terminal, 27 is ESC, 10 is newline, etc. |
| ^ | ( -- key) | read key from terminal, don't wait for newline. |
| " | ( -- ) | read string until next '"' put it on stdout |
| 0..9 | ( -- value) | scan decimal number until non digit. to push two values on stack separate those by space (4711 3333). to enter negative numbers call _ (negate) after the number |
| 0..9.0 | ( -- value) | to enter float numbers digits must contain one '.' (only available if float module is active, see 0`) |
| opcode | stack effects | description |
|---|---|---|
| < | (a b -- f) | true (-1) if b is < a, false (0) otherwise |
| > | (a b -- f) | true (-1) if b is > a, false (0) otherwise |
| = | (a b -- f) | true (-1) if a is equal to b, false (0) otherwise |
| ( | (f -- ) | if f is true, execute content until ), if false skip code until ')' |
| [ | (f -- f) | begin while loop only if f is true. keep flag on stack if f is false, skip code until ']' |
| ] | (f --) | repeat the loop if f is true. If f is false continue with code after ']' |