git mv *.hint -> README.md

There is one exception:

    $ find . -name '*.hint' -execdir git mv '{}' README.md \;
    git statufatal: destination exists, source=1992/albert/albert.hint, destination=1992/albert/README.md

Looking at the two files they differ quite a bit so I've not changed it.
I'll bring this up on GitHub.
This commit is contained in:
Cody Boone Ferguson committed 2023-02-08 05:47:28 -08:00
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Most complex algorithm:
Paul E. Black
CIRRUS LOGIC, Inc.
1463 Centre Pointe Dr.
Milpitas, CA
95035
USA
Judges notes:
The original source contained a long line which caused many
mailers to barf. The original file may be re-constructed by
removeing the trailing "\" on line 12 and joining lines 12 and
13 together without a space.
WHAT FOLLOWS IS A DETAILED PROGRAM EXPLINATION AND SPOILER.
IF YOU WANT A REAL CHALLENGE, DON'T READ ANY FURTHER AND TRY
TO UNDERSTAND THE PROGRAM VIA THE SOURCE.
Selected notes from the author:
This programs computes and prints Fibonacci numbers by
simulating a Turing machine with the proper program.
Understanding the C program, i.e., a Turing machine simulator,
is only the first and simplest step. The Turing machine
program must be understood, too! (it is trivial, perhaps even
natural to write incredibly obscure Turing programs.)
If the program is invoked with an operand, the operand is used
as the Turing program. It includes a "trace" facility,
subroutine r (commented out for obscurity), to help write and
debug Turing programs. Just the thing for some fun in a Theory
of Computation class.
The Turing machine tape is represented as a doubly linked list
of pointers. The forward and backward links are XOR'd together
and stored in one pointer. If we always keep one of the links
on hand, we can recover the other link at any time. The
variable q is the scan head (and a pointer at some tape cell),
and p is a "previous" link. The state of the tape is stored in
the low order bit of the pointer. Since we always allocate an
even number of bytes, the low order bit carries no information
(see portability below.) Memory representing a tape cell is
allocated when the cell is first scanned. Thus the simulation
begins with a tape effectively the size of virtual memory set
to all zeros. Since a header can be added to any Turing
program to write initial data and position the scan head, this
is little loss of generality.
The simulated Turing machine has a single tape with either an 1
or a 0 in each cell. The Turing machine language format is a
string of three bytes. The first byte is the current state.
The second byte is the next state. (The last bit of states is
ignored, e.g., B and C are the same state, in an attempt to be
able to have interesting words in the program.) The third byte
is composed of bits. Bit 1 (2&byte) is the symbol scanned,
i.e. an instruction is selected for state and for a match with
the symbol under the scan head. Bit 2 (4&byte) is the new
symbol to be written to the cell. Bit 3 (8&byte) is the
direction to move the scan head: 0 for left and 1 for right.
If bit 4 (16&byte) is true, the next character is sent to
stdout. (I added this feature so programs could print
results.)
The Turing machine has next state 'j' when it begins. The
cycle is 1) exit if the state is 'x', 2) find the next
instruction (given the state and the character under the scan
head). [The program string is searched forward for the next
matching instruction. If the end of the string is reached, the
search begins again at the first of the string. Thus states
can be used as local labels in different places.] 3) change to
the next state, 4) print a character if indicated, 5) write the
tape symbol, and 6) move the scan head. The cycle then repeats
with step 1. A call to the trace routine is just before step
2, but is commented out.
The following ROT13'ed text is a quick outline of the actual
Turing program:
Urer vf n dhvpx bhgyvar bs gur Ghevat cebtenz: gur
cerivbhf naq pheerag Svobanppv ahzoref ner xrcg va onfr
1 sbez jvgu gur pheerag ba gur evtug. Gur svefg guerr
fgrcf frg hc gur svefg gjb ahzoref, 1 naq 1. Gura
[ortvaavat jvgu "@ ("] n znexre bs VVV vf perngrq naq
gur pheerag ahzore vf pbcvrq gb gur evtug bs gur
znexre. Gura [ortvaavat jvgu "BI "] gur ahzore vf
pbairegrq gb ovanel ol ercrngrq qvivqvat ol 2 yrnivat V
sbe erznvaqre 1, naq VV sbe erznvaqre 0. Arkg
[ortvaavat jvgu "JI "] gur ovanel ercerfragngvba vf
cevagrq naq vgf flzobyf naq gur znexre ner renfrq.
Svanyyl [ortvaavat jvgu "RRa"] gur gjb ahzoref ner
nqqrq naq gur pheerag ahzore pbcvrq gb gur yrsg gb
orpbzr gur cerivbhf. Gura gur plpyr ercrngf.
The program requires that the lowest bit of a pointer to be 0.
I could have squeezed the program under 1024 bytes without the
trace subroutine, but I felt it was important for understanding
the program. Besides it is fun to watch the tape zooming back
and forth as the program runs. A much better debugger or trace
could easily be added.
Copyright (c) 1989, Landon Curt Noll & Larry Bassel.
All Rights Reserved. Permission for personal, educational or non-profit use is
granted provided this this copyright and notice are included in its entirety
and remains unaltered. All other uses must receive prior permission in writing
from both Landon Curt Noll and Larry Bassel.