add a readme

README.md

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+# 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
+```
+
+And, of course, it knows how to quit:
+
+```
+> BYE
+bye
+```
+
+## Future Plans
+
+* Implement `VARIABLE` and `CONSTANT` and the various `? ! @` related words
+* Implement `SEE`
+* 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...)