Landon Curt Noll
658669a73a
fix experimental web site links in experimental index.html sync CNAME with https://github.com/ioccc-src/winner/blob/master/CNAME improve .gitignore files Added to each .gitignore file, comments on how to sort. Put into winner .gitignore files, ignore *.dSYM files. Put into winner .gitignore files, ignore indent.c, indent.o and indent files. This is done so that the winner directory can more self contained. We did not put into winner .gitignore files, however, excludes of .-files as found in the top level .gitignore file. As .-files are not allowed by mkiocccentry, the top level .gitignore file remains sufficient. Added to year level .gitignore files, excludes of mkentry or iocccsize files as needed. Sorted (via sort -d -u) all .gitignore file.
To build:
make all
Bugs and (Mis)features:
The current status of this entry is:
STATUS: INABIAF - please **DO NOT** fix
For more detailed information see 1990 theorem in bugs.md.
To use:
./theorem expression x1 x2 h y1
where:
expression - function f(x,y) (see below)
x1 - start of interval
x2 - end of interval
h - step size
y1 - initial value (y(x1) == y1)
Try:
./theorem y 0 1 0.1 1
If the two args passed to fibonacci and theorem_bkp add to 0 it will
print 0 over and over again in an infinite loop. In this case it should not be
fixed (another condition where this occurred was fixed in 2023 as it affected
usability of the program).
This is supposed to happen. As is written in the The Jargon File:
That's not a bug, that's a feature.
Judges' remarks:
The program's source implements four functions, all from the same source file!
When you compile theorem.c as is and run with 5 args, it
numerically solves the equation y'=f(x,y), with a step size of h (see above
usage), over the interval x=[x1,x2], with the initial condition of y(x1)=y1.
The 'expression' f(x,y) is any function of x and y with the
operators:
+ - * / ^
The symbol ^ is the power operator. Note that it only supports
integer powers. Also note that all expressions are evaluated strictly
left to right. (i.e., parenthesis aren't supported).
Try running the program with the following args:
./theorem y 0 1 0.1 1
./theorem 1/x 1 2 0.1 0
./theorem 'x^2/y+x' 0 1 0.1 6
But wait, there is more! You also get, free of charge, a reversing filter! Try:
./theorem -r 0 0 0 0 < theorem.c > sorter.c
Still not impressed? The author throws in for free, a sort program! Try:
make sorter
ls | ./sorter
This program is safe for home use as well. The author has included a safety feature in case you misplace the original program source:
./sorter -r 0 0 0 0 < sorter.c > theorem_bkp.c
And finally, as a special offer to users of this entry, the author provides a Fibonacci sequence generator! Try:
./sorter 0 0 0 0 < theorem.c > fibonacci.c
make fibonacci
./fibonacci 1 1
./fibonacci 2 1
Program available on 9 track and cartridge cassette. Neither Ginsu knife nor Swiss army knife included! :-)
When this program was first shown at the 1990 Summer USENIX conference, it received a standing ovation; a first for a contest entry.
Author's remarks:
Differential equations are solved via the Runge-Kutta method, which guarantees
local error proportional to h^5, and total error across a finite interval is at
most a constant times h^4.
Sorting is accomplished with a standard shell sort.
Note that the sorting and reversing is limited to files with fewer than 500 lines, each less than 99 characters long.
Copyright and CC BY-SA 4.0 License:
This file is Copyright (c) 2023 by Landon Curt Noll. All Rights Reserved. You are free to share and adapt this file under the terms of this license:
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
For more information, see: https://creativecommons.org/licenses/by-sa/4.0/