Fix 2000/rince/README.md + update bugs.md
There is a known crash in the program if DISPLAY is unset. Typo fixed and format fixed.
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@@ -19,6 +19,11 @@ make
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./rince number number2
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```
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### INABIAF - it's not a bug it's a feature! :-)
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If `DISPLAY` is not set the program will very likely crash or do something
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different.
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## Try:
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```sh
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@@ -28,11 +33,11 @@ make dmy2jd
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## Judges' remarks:
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This program may have you going around in circles :-) Try running it
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first before reading the author's remarks below.
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This program may have you going around in circles :-) Try running it first
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before reading the author's remarks below.
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The judges verified the correctness of output for recent dates
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through visual observation.
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The judges verified the correctness of output for recent dates through visual
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observation.
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## Author's remarks:
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@@ -67,19 +72,22 @@ Julian day number (given as a fractional component). E.g.:
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./rince 0.01 2441193.6
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```
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A Julian day is defined to be the number of days since January 1st in
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the year -4712 (4713BC), starting at 12 noon GMT.[1] To aid conversion
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from our time (GMT) to Julian day there is a supplementary program
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named: dmy2jd.c. Run it with `day_float month year` as arguments. See
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below for an example.
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A Julian day is defined to be the number of days since January 1st in the year
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`-4712 (4713BC)`, starting at 12 noon GMT.\[1\] To aid conversion from our time
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(GMT) to Julian day there is a supplementary program named:
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[dmy2jd.c](dmy2jd.c). Run it with `day_float month year` as arguments. See below
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for an example.
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### What it does
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This program plots the positions of the four Galilean moons of Jupiter,
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as seen from earth. It doesn't correct for your location on earth, but I
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assure you that the parallax is minimal!
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This program plots the positions of the four [Galilean
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moons](https://en.wikipedia.org/wiki/Galilean_moons) of
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[Jupiter](https://en.wikipedia.org/wiki/Jupiter), as seen from
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[Earth](https://en.wikipedia.org/wiki/Earth). It doesn't correct for your
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location on Earth, but I assure you that the
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[parallax](https://en.wikipedia.org/wiki/Parallax#Astronomy) is minimal!
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The moons are labelled with roman numerals from I to IV. I being the
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The moons are labelled with Roman numerals from I to IV. I being the
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closest to the planet and IV being the furthest. They are:
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```
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@@ -174,39 +182,46 @@ Galileo discovered the fourth moon a few days later.
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I've tried typing these dates in to two Java based Jovian moon plotters,
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but both I tried had problems dealing with dates earlier than 1900. More
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professional software, such as the SkyMap program [3] gets these values
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professional software, such as the
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[SkyMap](http://www.bmsoftware.com/skymappro9.htm) gets these values
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correct and this compares well with the above description and with this
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IOCCC entry.
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The year 4713BC was chosen by Joseph Justus Scaliger in the 16th Century,
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so clearly this program has a long history :-) A more complete description
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of the origins of Julian Days can be found at
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The year 4713BC was chosen by [Joseph Justus
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Scaliger](https://en.wikipedia.org/wiki/Joseph_Justus_Scaliger) in the 16th
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Century, so clearly this program has a long history :-) A more complete
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description of the origins of Julian Days can be found at
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<https://web.archive.org/web/20001206152200/http://aa.usno.navy.mil/AA/faq/docs/millennium.html>.
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### Assumptions
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This program assumes:
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1. The ASCII character set is used.
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2. That an enormous comet hasn't changed the course of Jupiter (or Earth!).
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3. That the date has not been specified as the gap between the Julian and Gregorian calendar.
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3. That the date has not been specified as the gap between the
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[Julian](https://en.wikipedia.org/wiki/Julian_calendar) and
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[Gregorian](https://en.wikipedia.org/wiki/Gregorian_calendar) calendar.
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4. That the DISPLAY environment variable is set and the X display can opened. If this is not the case the program will crash.
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4. That the `DISPLAY` environment variable is set and the X display can opened.
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If this is not the case the program will crash.
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5. There is a year 2000BC problem :-)
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More specifically, the plots for dates that far back are too inaccurate
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to be of realistic use. Comparisons against SkyMap Pro [3] show that
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there is a good similarity (but not much more) up to about 500BC.
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More specifically, the plots for dates that far back are too inaccurate to
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be of realistic use. Comparisons against [SkyMap
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Pro](http://www.bmsoftware.com/skymappro9.htm) show that there is a good
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similarity (but not much more) up to about 500BC.
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6. The code definitely is not portable - it will produce incorrect results if run from the surface of Mars.
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### Obfuscations
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In addition to the normal obfuscations, I feel that the code contains
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some less common tricks. Taken through the standard rounds listed in the
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guidelines, the code attempts to pass these as follows:
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In addition to the normal obfuscations, I feel that the code contains some less
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common tricks. Taken through the standard rounds listed in the
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[guidelines](/2000/guidelines.txt), the code attempts to pass these as follows:
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1. Look at the original source
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@@ -219,26 +234,26 @@ guidelines, the code attempts to pass these as follows:
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large string constant could not be split up using a "partA"
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"partB" method which clearly limits the code layout. However the
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space saved by using a single long string constant is more than
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outweighed by ability to further obfuscate.
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outweighed by the ability to further obfuscate.
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2. convert ANSI tri-graphs to ASCII
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These are not used.
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3. C pre-process the source ignoring #include lines
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4. C pre-process the source ignoring #define and #include lines
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3. C pre-process the source ignoring `#include` lines
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4. C pre-process the source ignoring `#define` and `#include` lines
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This does a good job of expanding out the code, but it does not
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clarify things greatly. The use of #defines has been restricted
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clarify things greatly. The use of `#defines` has been restricted
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primarily to a space-saving mechanism.
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Additionally, the use of typedefs means that the types used are
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Additionally, the use of `typedef`s means that the types used are
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still obscured unless further replacement edits are made.
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5. Run it through a C beautifier.
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GNU indent seems to do a reasonable job, provided that the
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#defines are expanded first. This doesn't lay the algorithm
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`#define`s are expanded first. This doesn't lay the algorithm
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particularly bare though as most of the obfuscations are not
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simple code layouts.
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@@ -246,15 +261,14 @@ guidelines, the code attempts to pass these as follows:
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The algorithm operates on two levels. The main visible level is
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by taking a large string and breaking this down into a series of
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op-codes (which I have termed J-code). These are then executed.
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opcodes (which I have termed J-code). These are then executed.
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To get to the real method of how it works, you need to decode
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the op-code string (which deliberately contains as many ; { and
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} symbols as possible), which will give you a reverse-polish
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the opcode string (which deliberately contains as many `;`, `{` and
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`}` symbols as possible), which will give you a reverse-polish
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notation chunk of mathematics.
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Sensible people amongst you will simply refer to the referenced
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book :-)
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Sensible people amongst you will simply refer to the referenced book :-)
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7. Lint it.
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@@ -269,69 +283,63 @@ guidelines, the code attempts to pass these as follows:
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I'm sorry to say that there are several warnings issued by the
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compiler.
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Firstly, the return type for X() is not specified, so it
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defaults to int. Horror of all horrors - this function does not
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return an integer type (it doesn't contain any specific
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returns). The return value from X() is not accessed. The same
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problem occurs in main - it does not return. However main never
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exits unless there is a serious error.
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Firstly, the return type for `X()` is not specified, so it defaults to int.
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Horror of all horrors - this function does not return an integer type (it
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doesn't contain any specific returns). The return value from `X()` is not
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accessed. The same problem occurs in `main()` - it does not return. However
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`main()` never exits unless there is a serious error.
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The 6th argument of XDrawText (which should be XTextItem) is
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The 6th argument of `XDrawText` (which should be `XTextItem`) is
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passed as a compatible structure, but without casting. This is
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to reduce code space. A more elegant solution is to remove the
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"struct {...} Z" completely and use "XTextItem
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f={i-127+r/3*2,r%3+r/3+1,0,E}" at the start of XDrawText
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`struct {...} Z` completely and use `XTextItem
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f={i-127+r/3*2,r%3+r/3+1,0,E}` at the start of `XDrawText`
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block. Although this is accepted by several compilers, it is not
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strict ANSI due to the non-constant initialisers. A pity.
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Note that I make use of usleep(). This is a POSIX call (it is
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BSD), but it supported on many systems. It may be implemented
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using select() or poll() if required, or as a final solution you
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may change the usleep(10000) to sleep(1). To compile on systems
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which do not have usleep, but do have select, the following may
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suffice as an additional compiler argument:
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Note that I make use of `usleep()`. This is a POSIX call (it is BSD), but it's
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supported on many systems. It may be implemented using `select()` or `poll()` if
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required, or as a final solution you can change the `usleep(10000)` to
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`sleep(1)`. To compile on systems which do not have `usleep()`, but do have
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`select()`, the following may suffice as an additional compiler argument:
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```sh
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-Dusleep={time_t v[2]={0,10000};select(0,0,0,0,v);}
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```
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```
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-Dusleep={time_t v[2]={0,10000};select(0,0,0,0,v);}
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```
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Gcc complains about "unreachable code at beginning of switch
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gcc complains about "unreachable code at beginning of switch
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statement", although removing some of this code will prevent
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the algorithm from working.
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Gcc also suggests that I should be using extra parenthesis, but
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gcc also suggests that I should be using extra parenthesis, but
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I'm taking this as good comment :-)
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In addition to the above, the program has the following useful(?)
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obfuscations:
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1. The algorithm requires many floating point numbers (about
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50). These are encoded as ASCII.
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1. The algorithm requires many floating point numbers (about 50). These are
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encoded as ASCII.
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2. The J-code algorithm has op-codes designed to be space
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saving. They are all one byte, but many are also considered as
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white-space by the rules. This algorithm forms part of the same
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string that the floating point constants are embedded
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within. What does the ";" command do in J-code?
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2. The J-code algorithm has opcodes designed to be space saving. They are all
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one byte, but many are also considered as whitespace by the rules. This
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algorithm forms part of the same string that the floating point constants are
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embedded within. What does the `;` command do in J-code?
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3. The J-code language is both stack based and variable based. This
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"uncleanliness" is not ideal from a computer science angle, but
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when has cleanliness been considered as good in IOCCC? :-)
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3. The J-code language is both stack based and variable based. This
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"uncleanliness" is not ideal from a computer science angle, but when has
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cleanliness been considered as good in IOCCC? :-)
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4. Association of unconnected data by implied function usage. Eg
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use of strlen() and sizeof() simply to return useful numerical
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values, using irrelevant arguments.
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4. Association of unconnected data by implied function usage. E.g. use of
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`strlen()` and `sizeof()` simply to return useful numerical values, using
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irrelevant arguments.
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5. As we already have a dependency on ASCII this has been abused
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further. Specifically some integer constants are specified as
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ASCII and some ASCII constants are integers. This hides the true
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meaning for the values.
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5. As we already have a dependency on ASCII this has been abused further.
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Specifically some integer constants are specified as ASCII and some ASCII
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constants are integers. This hides the true meaning for the values.
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6. Red herrings: there's a couple of pieces of code whose
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appearance is just there to mislead the unfirm of mind.
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I've only tried to include such examples in places where at
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first glance the code appears to be executed.
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6. Red herrings: there are a couple of pieces of code whose appearance is just
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there to mislead the infirm of mind. I've only tried to include such examples
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in places where at first glance the code appears to be executed.
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### References
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@@ -341,9 +349,6 @@ Jean Meeus. Published by Willmann-Bell Inc.
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[2] Astronomical algorithms (1st ed): pages 285-299.
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Jean Meeus. Published by Willmann-Bell Inc.
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[3] Skymap Pro, by Chris Marriott
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http://www.skymap.com/
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## Copyright and CC BY-SA 4.0 License:
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This file is Copyright (c) 2023 by Landon Curt Noll. All Rights Reserved.
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@@ -1019,6 +1019,13 @@ fix this (in fact it was originally done but rolled back).
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As well there is a known crash that's also a feature.
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## [2000/rince](2000/rince/rince.c) ([README.md](2000/rince/README.md))
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## STATUS: INABIAF - please **DO NOT** fix
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If `DISPLAY` is not set the program will very likely crash, do something strange
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(or if you're very unlucky your computer might [halt and catch
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fire](https://en.wikipedia.org/wiki/Halt_and_Catch_Fire_(computing))! :-) ).
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# 2001
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Reference in new issue
Block a user