lab 48 - symbol

By

NAME

lab 48 - symbol

NOTES

I'm clearing out the backlog and found this lab's code, which is really a continuation of earlier labs on the lispy-shell (26, 27, 28). I felt that where I was going with lab 28 wasn't working out, or was just going to end up looking like scsh (if I was lucky, and as smart as Olin Shivers).

This attempt is more a mathematica-like-shell, and for a while was looking better, in that it fit in better with the existing sh, but now I've decided against it too. I'm posting it here just to record what I've done. I'll try and explain at the end why I don't like this approach anymore.

In Mathematica everthing is an expression of the form 

f[x,y]

which translates quite easily into the shell expression 

f x y

Because of Inferno sh's command blocks, we can directly support the nesting in expressions: 

% Head {f x y}
f
% Head {f;x;y}
List
# a sequence of commands {f;x;y} is 
# represented as {List f x y} in "FullForm"

And so, because of command blocks and this simple represenation of expressions, any arbitrarily complex structure can be represented in sh syntax and a sh module that implemented the core set of Mathematica commands could be used to symbolically manipulate that data.

Here are a few more to give you an idea. 

% Length {a;b;c;d;e;f;g}
7
% Rest {a;b;c;d}
{b;c;d}
% Apply f {a;b;c;d}
{f a b c d}
% Map f {a;b;c;d}
{f a; f b; f c; f d}
% Nest f a 3
{f {f {f a}}}

Another crucial idea of Mathematica is its peculiar "infinite evaluation" system; it keeps evaluating an expression until it no longer changes. I implemented IEval builtin which takes the output of a command and evaluates it again until the output is the same as the input. 

% IEval {Point 1 2 3}
{Point 1 2 3}

But I stopped short of implementing the evaluation system described in the Mathematica docs. It was at this point that I realized what I was doing was just a pipeline from sh to sh, and that maybe the commands should read standard input for symbolic data. And then maybe they should be programmable using regular expressions and accept an arbitrary text stream instead of specifically structured text based on sh syntax. And at that point I'm back with the UNIX philosophy of software tools.

So I arrived at the point where even though symbol would fit within sh it might not fit within Inferno. From this exercise I think I have a better appreciation of the existing set of Inferno software tools. It is not always obvious how they are applied to a problem. But sometimes one needs to take a long trip around the computer science field before one can understand their generality, and that a command block is just quoted text; and quoted text is just a text stream.

FILES

caerwyn.com/lab/48

Comments

Post a Comment

Popular posts from this blog

lab 110 - inferno archive edition

By
I've been occupied recently with archiving my digital media. I've been copying home videos on DV tapes to hard-disk, ripping audio CD's to WAV files, gathering photo collections, and trying to copy documents from Iomega disks, floppies, and my dusty old Acorn RiscPC. The plan is to have a copy of this data to give to each of my children. My Dad recently scanned and sent me all his photographs of me and my siblings growing up; he also included pictures of himself and my Mother when they met in Africa. With technology today each generation can build a digital library of family history to hand on to the next generation. In the past a family album may have been passed on to only one person. The accumulation of digital data still presents problems. It requires discipline to store files that are open and not locked into devices or proprietary formats. With digital preservation in mind I've tried to use file formats recommended for long term archiving. WAV files for audio, D
Read more

lab 107 - midiplay

By
NAME lab 107 - midiplay NOTES Midiplay plays back MIDI files. It uses the synthesizer I described in lab 62 and the MIDI module from lab 73. The command takes only one argument, the path to the midi file. I've included one in the lab to demonstrate. Bind the audio device before using it. % bind -a '#A' /dev % midiplay invent15.mid The synthesizer has 16 note polyphony. It uses three oscillators, one at the pitch, one at half pitch, one at double pitch. There is also a filter, two delays and a vibrato. The sample rate is 8000hz and there is one mono channel (MIDI channel events are ignored). It performs well enough to work on my laptop without JIT turned on. All the synthesizer parameters can only be tweaked from inside the code at the moment. FILES lab - 107
Read more

The Cartesian Theater of AI

By
Image
The Cartesian Theater was an intuition pump proposed by philosopher Daniel Dennett to describe a false theory of consciousness. Inside the mind is a stage watched by a humunculus that observes what passes on the stage, hears the sounds, and controls the rest of the mind by responding to the action of what the smaller version of the self sees. Of course, what makes the smaller self conscious? It is an infinite regression. Our understanding of mind is that there is no such theater. There is no one place in the mind that is the locality of consciousness. I want to offer another thought experiment based on the concept of a Cartesian Theater. Imagine a theater containing a screen with a camera pointing at it, and a speaker with a microphone directed toward the speaker. The camera is pointing at the screen. The mic is pointing at the speaker. However, instead of there being an infinite loop due to a direct connection between the camera and screen, insert an AI in the loop. The imag
Read more