121 lines
6.1 KiB
HTML
121 lines
6.1 KiB
HTML
|
<?xml version="1.0" encoding="utf-8"?>
|
||
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
|
||
|
|
<html xmlns="http://www.w3.org/1999/xhtml"><head>
|
||
|
|
<title>.</title>
|
||
|
|
<style type="text/css">
|
||
|
|
|
||
|
|
* { color: #000; background: #fff; max-width: 700px; }
|
||
|
|
tt, pre { background: #dedede; color: #111; font-family: monospace;
|
||
|
|
white-space: pre; display: block; width: 100%; }
|
||
|
|
.indentedcode { margin-left: 2em; margin-right: 2em; }
|
||
|
|
.codeblock {
|
||
|
|
background: #dedede; color: #111; font-family: monospace;
|
||
|
|
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
|
||
|
|
padding: 7px;
|
||
|
|
display: block;
|
||
|
|
}
|
||
|
|
|
||
|
|
.indentedlist { margin-left: 2em; color: #000; }
|
||
|
|
|
||
|
|
span { white-space: pre; }
|
||
|
|
.text { color: #000; white-space: pre; background: #dedede; }
|
||
|
|
.colon { color: #000; background: #dedede; }
|
||
|
|
.note { color: #000; background: #dedede; }
|
||
|
|
.str { color: #000; text-decoration: underline; background: #dedede; }
|
||
|
|
.num { color: #000; background: #dedede; font-weight: bold; font-style: italic; }
|
||
|
|
.fnum { color: #000; font-weight: bold; background: #dedede; }
|
||
|
|
.ptr { color: #000; font-weight: bold; background: #dedede; }
|
||
|
|
.fetch { color: #000; font-style: italic; background: #dedede; }
|
||
|
|
.store { color: #000; font-style: italic; background: #dedede; }
|
||
|
|
.char { color: #000; background: #dedede; }
|
||
|
|
.inst { color: #000; background: #dedede; }
|
||
|
|
.defer { color: #000; background: #dedede; }
|
||
|
|
.imm { color: #000; font-weight: bold; background: #dedede; }
|
||
|
|
.prim { color: #000; font-weight: bolder; background: #dedede; }
|
||
|
|
|
||
|
|
.tt { white-space: pre; font-family: monospace; background: #dedede; }
|
||
|
|
|
||
|
|
.h1, .h2, .h3, .h4 { white-space: normal; }
|
||
|
|
.h1 { font-size: 125%; }
|
||
|
|
.h2 { font-size: 120%; }
|
||
|
|
.h3 { font-size: 115%; }
|
||
|
|
.h4 { font-size: 110%; }
|
||
|
|
.hr { display: block; height: 2px; background: #000000; }
|
||
|
|
</style>
|
||
|
|
</head><body>
|
||
|
|
<p><span class="h2">On The Evolution Of Ngaro Into Nga</span>
|
||
|
|
<br/><br/>
|
||
|
|
When I decided to begin work on what became RETRO 12, I knew
|
||
|
|
the process would involve updating Ngaro, the virtual machine
|
||
|
|
that RETRO 10 and 11 ran on.
|
||
|
|
<br/><br/>
|
||
|
|
Ngaro rose out of an earlier experimental virtual machine I had
|
||
|
|
written back in 2005-2006. This earlier VM, called Maunga, was
|
||
|
|
very close to what Ngaro ended up being, though it had a very
|
||
|
|
different approach to I/O. (All I/O in Maunga was intended to be
|
||
|
|
memory mapped; Ngaro adopted a port based I/O system).
|
||
|
|
<br/><br/>
|
||
|
|
Ngaro itself evolved along with RETRO, gaining features like
|
||
|
|
automated skipping of NOPs and a LOOP opcode to help improve
|
||
|
|
performance. But the I/O model proved to be a problem. When I
|
||
|
|
created Ngaro, I had the idea that I would always be able to
|
||
|
|
assume a console/terminal style environment. The assumption was
|
||
|
|
that all code would be entered via the keyboard (or maybe a
|
||
|
|
block editor), and that proved to be the fundamental flaw as
|
||
|
|
time went on.
|
||
|
|
<br/><br/>
|
||
|
|
As RETRO grew it was evident that the model had some serious
|
||
|
|
problems. Need to load code from a file? The VM and language had
|
||
|
|
functionality to pretend it was being typed in. Want to run on
|
||
|
|
something like a browser, Android, or iOS? The VM would need to
|
||
|
|
be implemented in a way that simulates input being typed into
|
||
|
|
the VM via a simulated keyboard. And RETRO was built around this.
|
||
|
|
I couldn't change it because of a promise to maintain, as much
|
||
|
|
as possible, source compatibility for a period of at least five
|
||
|
|
years.
|
||
|
|
<br/><br/>
|
||
|
|
When the time came to fix this, I decided at the start to keep
|
||
|
|
the I/O model separate from the core VM. I also decided that the
|
||
|
|
core RETRO language would provide some means of interpreting
|
||
|
|
code without requiring an assumption that a traditional terminal
|
||
|
|
was being used.
|
||
|
|
<br/><br/>
|
||
|
|
So Nga began. I took the opportunity to simplify the instruction
|
||
|
|
set to just 26 essential instructions, add support for packing
|
||
|
|
multiple instructions per memory location (allowing a long due
|
||
|
|
reduction in memory footprint), and to generally just make a far
|
||
|
|
simpler design.
|
||
|
|
<br/><br/>
|
||
|
|
I've been pleased with Nga. On its own it really isn't useful
|
||
|
|
though. So with RETRO I embed it into a larger framework that
|
||
|
|
adds some basic I/O functionality. The <strong>interfaces</strong> handle the
|
||
|
|
details of passing tokens into the language and capturing any
|
||
|
|
output. They are free to do this in whatever model makes most
|
||
|
|
sense on a given platform.
|
||
|
|
<br/><br/>
|
||
|
|
So far I've implemented:
|
||
|
|
<br/><br/>
|
||
|
|
<tt class='indentedcode'>- a scripting interface, reading input from a file and</tt>
|
||
|
|
<tt class='indentedcode'> offering file i/o, gopher, and reading from stdin, and</tt>
|
||
|
|
<tt class='indentedcode'> sending output to stdout.</tt>
|
||
|
|
<tt class='indentedcode'>- an interactive interface, built around ncurses, reading</tt>
|
||
|
|
<tt class='indentedcode'> input from stdin, and displaying output to a scrolling</tt>
|
||
|
|
<tt class='indentedcode'> buffer.</tt>
|
||
|
|
<tt class='indentedcode'>- an iOS interface, built around a text editor, directing</tt>
|
||
|
|
<tt class='indentedcode'> output to a separate interface pane.</tt>
|
||
|
|
<tt class='indentedcode'>- an interactive block editor, using a gopher-based block</tt>
|
||
|
|
<tt class='indentedcode'> data store. Output is displayed to stdout, and input is</tt>
|
||
|
|
<tt class='indentedcode'> done via the blocks being evaluated or by reading from</tt>
|
||
|
|
<tt class='indentedcode'> stdin.</tt>
|
||
|
|
<br/><br/>
|
||
|
|
In all cases, the only common I/O word that has to map to an
|
||
|
|
exposed instruction is <span class="tt">putc</span>, to display a single character to
|
||
|
|
some output device. There is no requirement for a traditional
|
||
|
|
keyboard input model.
|
||
|
|
<br/><br/>
|
||
|
|
By doing this I was able to solve the biggest portability issue
|
||
|
|
with the RETRO 10/11 model, and make a much simpler, cleaner
|
||
|
|
language in the end.
|
||
|
|
</p>
|
||
|
|
</body></html>
|