Landon Curt Noll
7712db4a17
Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:
```sh
find * -type f -name '*.md' -print |
while read -r file; do
rm -f "$file.tmp" ;
expand < "$file" > "$file.tmp" ;
mv -f -v "$file.tmp" "$file" ;
done
```
Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files. This is a **good thing** as the expression goes.
No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.
BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.
Perform `make www` to perform the above and test under macOS.
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.html.
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:
./try.sh
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
NOTE: 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).
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.