Prosper

Prosper is a Forth-like stack-based language. While taking specific influence from Forth, it does not attempt to emulate or implement the ANS Forth standards.

Currently, the language is entirely interactive -- to explore, simply run go run . in the root of this project and an interactive session will begin.

Syntax

Prosper is stack-based, as mentioned, so all the standard stack semantics are present:

> 1 2 3 4 + * -
ok
> .
-13 ok

New words can be defined using : ;:

> : SQUARE DUP * ;
ok
> 10 SQUARE .
100 ok

It has a single loop construct, DO LOOP:

> : TOFIVE 5 0 DO I . LOOP ;
ok
> TOFIVE
0 1 2 3 4 ok

Branches using IF ELSE THEN work:

> : EMOJI 0 < IF 128201 EMIT ELSE 128200 EMIT THEN ;
ok
> 100 EMOJI 
📈 ok
> -100 EMOJI
📉 ok

Here's a Fibonacci implementation:

> : FIB 2DUP + ;
ok
> : FIBN 0 1 ROT 1 DO FIB ROT DROP LOOP SWAP DROP ;
ok
> 10 FIBN .
55 ok

Propser also has a basic off-stack memory model using variables, constants, and pointers:

> VARIABLE FOO
ok
> 10 FOO !
ok
> FOO @
ok
> .
10 ok
> 100 CONSTANT HUNDRED
ok
> HUNDRED HUNDRED * .
10000 ok

And, of course, it knows how to quit:

> BYE
bye

Future Plans

• Implement loading libraries of pre-written functions both from the command-line and at run-time
• Add much better readline behaviors in the interactive console (up-arrow for history, cursor movement...)