Landon Curt Noll
8b71dd0d4f
The entries referenced in `bugs.md` now have, below the "To build:" section, a "Bugs and (Mis)features section text" that matches the `bugs.md` status. Several entries had their "STATUS" changed from: "STATUS: INABIAF - please **DO NOT** fix" to: "STATUS: known bug - please help us fix": This was done because, while some of the bugs were minor, inviting someone to try and fix the issue does nil harm. In a few cases a more difficult bug was also changed to the "please help us fix". While we do NOT want to waste time fixing such entries NOW, letting others become involved and to try to fix the entry is a good thing as to encourages people to study the entry and try to fix the entry. We don't need to accept a fix that is offered, and of the fix transforms the source in a less than desirable way, such a fix (if accepted) could be become a alt source code.
Best of Show
Adrian Mariano
University of Washington
2729 72nd Ave SE
Mercer Island, WA 98040
US
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
INABIAF - it's not a bug it's a feature! :-)
If the two args passed to fibonacci and theorem_bkp equals 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 as it affected usability
of the program).
BTW: why can't the fix:
if (a[1]==NULL||a[2]==NULL||a[3]==NULL||a[4]==NULL||a[5]==NULL) return 1;
be changed to just test the value of A when a is argv and A is argc?
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/