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# Reverse Polish Scheme
A continuation-passing-style stack-based programming language vaguely
based off of FORTH but really just Scheme in disguise. With the exception
of quotation (which is syntax), everything is RPN.
## Core
Writing a number, a string, `#t`, `#f`, or `#nil` will push that literal
value onto the stack. Strings are equivalent to Scheme symbols. `#nil`
is the name of a value, NOT the symbol `"nil"`!
A linked list is a 2-vector whose second pair is either `#nil` or
another linked list.
A subroutine is a linked list whose first slot is unused and whose code
starts in the second slot.
* `n alloc`: Allocate a memory region of `n` pointers.
* `{ ... }`: Reads all data up to the matching `{` as data. The data
is stored as a linked list.
* `n v ref`: Get the nth element of `v`.
* `value n v set!`: Set the nth element of `v`.
* `sr jump`: Jump to a subroutine.
* `conditional on-false on-true if`: If `conditional` is truthy, jump
to `on-true`. Otherwise jump to `on-false`.
* `keep-bot keep-top push-cc`: Push the *continuation* of the call to
`push-cc`. The continuation object saves the last `keep-top` objects
on the stack along with the bottom `keep-bot` values on the stack. If
either is `#f`, then the entire stack is saved.
When `m cc jump` is called (where `cc` is the object returned by
`push-cc`), the `m` values currently on the stack are pushed to the top
of `n` values saved by `cc`, and control returns to the next location.
* `dir? n dig`: When `dir?` is false, move the `n`th value relative to the
top of the stack to the top of the stack. When `dir?` is true, move the
`n`th value relative to the bottom of the stack to the top of the stack.
* `dir? n bury`: When `dir?` is false, move the top value on the stack to
the `n`th value relative to the top of the stack. When `dir?` is true,
move the top of the stack to `n`th value relative to the bottom of
the stack.
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