2019-03-18 15:52:49 +01:00
|
|
|
# Stack Diagrams
|
|
|
|
|
|
|
|
|
|
Most words in RETRO have a stack comment. These look like:
|
|
|
|
|
|
|
|
|
|
(-)
|
|
|
|
|
(nn-n)
|
|
|
|
|
|
|
|
|
|
As with all comments, a stack comment begins with `(` and
|
|
|
|
|
should end with a `)`. There are two parts to the comment.
|
|
|
|
|
On the left side of the `-` is what the word *consumes*. On
|
|
|
|
|
the right is what it *leaves*.
|
|
|
|
|
|
|
|
|
|
RETRO uses a short notation, with one character per value
|
|
|
|
|
taken or left. In general, the following symbols represent
|
|
|
|
|
certain types of values.
|
|
|
|
|
|
2020-02-12 15:50:49 +01:00
|
|
|
| Notation | Represents |
|
|
|
|
|
| ------------------- | ----------------------- |
|
|
|
|
|
| b, n, m, o, x, y, z | generic numeric values |
|
|
|
|
|
| s | string |
|
|
|
|
|
| v | variable |
|
|
|
|
|
| p, a | pointers |
|
|
|
|
|
| q | quotation |
|
|
|
|
|
| d | dictionary header |
|
|
|
|
|
| f | `TRUE` or `FALSE` flag. |
|
2019-03-18 15:52:49 +01:00
|
|
|
|
|
|
|
|
In the case of something like `(xyz-m)`, RETRO expects z to be
|
|
|
|
|
on the top of the stack, with y below it and x below the y
|
|
|
|
|
value. And after execution, a single value (m) will be left on
|
|
|
|
|
the stack.
|
|
|
|
|
|
|
|
|
|
Words with no stack effect have a comment of (-)
|
