Opinions
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mmm... last week? maybe the week before?
it sure has a modern je-ne-sais-quoi. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.
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Hey folks, I don't generally post on these forums, but I do enjoy the CP newsletters. Anyways, I wanted to share a lovely snippet I wrote a little while ago. Maybe get some opinions? It's a bubble sort in C. It generates 20 random numbers from 0 to 99, and sorts them! Of course, it's fairly straightforward, so I'm sure you could guess that.
#include <stdlib.h>
#include <stdio.h>
#include <time.h>#define ARRAY_SIZE 20
#define PNT(s, l, a) fprintf(std##s, l, a)
#define PNT2LINES(s, l1, l2, e) PNT(s, #l1#e#l2#e, 0)void print_array(int *array) {
int x = ARRAY_SIZE;
char* fmts[] = { "%d, ", "%d\n" };
--array;
LBL0:
if (PNT(out, ((x == 1) & 1)[fmts], *(array = ++array)), --x > 0)
goto LBL0;
}main() {
int iarray[ARRAY_SIZE];
int x, y;
int ofs = iarray - &ofs;
void (*prnt_func)(int*) = &print_array;
srand((unsigned int)time(NULL));
x ^= x;
LBL1:
if ((y = rand(), x < ARRAY_SIZE) && ((((x = x + 1) - 1)[iarray] = (y - (y / 100) * 100)) || 1))
goto LBL1;
PNT2LINES(out, Before sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
LBL2:
y = x &= ~x;
LBL3:
if (y + 1 < ARRAY_SIZE) {
if ((++y, iarray[y] < (y-1)[iarray]) && (y[iarray] ^= iarray[y-1] ^= iarray[y] ^= *(iarray + y - 1), x |= y));
goto LBL3;
}
if (x = x) goto LBL2;
PNT2LINES(out, After sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
} -
I personally liked the use of function pointers for a simple method call ;P
The shout of progress is not "Eureka!" it's "Strange... that's not what i expected". - peterchen
That, of course, is so that I can change the function name, and only need to change one place where it's used. Gotta think about maintainability and future modifications!
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Hey folks, I don't generally post on these forums, but I do enjoy the CP newsletters. Anyways, I wanted to share a lovely snippet I wrote a little while ago. Maybe get some opinions? It's a bubble sort in C. It generates 20 random numbers from 0 to 99, and sorts them! Of course, it's fairly straightforward, so I'm sure you could guess that.
#include <stdlib.h>
#include <stdio.h>
#include <time.h>#define ARRAY_SIZE 20
#define PNT(s, l, a) fprintf(std##s, l, a)
#define PNT2LINES(s, l1, l2, e) PNT(s, #l1#e#l2#e, 0)void print_array(int *array) {
int x = ARRAY_SIZE;
char* fmts[] = { "%d, ", "%d\n" };
--array;
LBL0:
if (PNT(out, ((x == 1) & 1)[fmts], *(array = ++array)), --x > 0)
goto LBL0;
}main() {
int iarray[ARRAY_SIZE];
int x, y;
int ofs = iarray - &ofs;
void (*prnt_func)(int*) = &print_array;
srand((unsigned int)time(NULL));
x ^= x;
LBL1:
if ((y = rand(), x < ARRAY_SIZE) && ((((x = x + 1) - 1)[iarray] = (y - (y / 100) * 100)) || 1))
goto LBL1;
PNT2LINES(out, Before sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
LBL2:
y = x &= ~x;
LBL3:
if (y + 1 < ARRAY_SIZE) {
if ((++y, iarray[y] < (y-1)[iarray]) && (y[iarray] ^= iarray[y-1] ^= iarray[y] ^= *(iarray + y - 1), x |= y));
goto LBL3;
}
if (x = x) goto LBL2;
PNT2LINES(out, After sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
}Check out the following hidden and tricky features of C: FOR statemnt[^] Commentaries[^] And DO NOT USE GOTO[^]
Greetings - Jacek
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Check out the following hidden and tricky features of C: FOR statemnt[^] Commentaries[^] And DO NOT USE GOTO[^]
Greetings - Jacek
Wow! For loops are neat! I rewrote my code, got rid of the gotos, used for loops, and put in some comments like in the article you linked to. I think it's much improved now. I'm especially proud of my reduction of the number of loops. The main sorting part used to involve two nested loops (one inside the other), but I was able to reduce it to a single loop!
#include <stdlib.h>
#include <stdio.h>
#include <time.h>#define ARRAY_SIZE 20
#define PNT(s, l, a) fprintf(std##s, l, a)
#define PNT2LINES(s, l1, l2, e) PNT(s, #l1#e#l2#e, 0)void print_array(int *array) {
int x = ARRAY_SIZE;
char* fmts[] = { "%d, ", "%d\n" }; /* fmts has two strings in it */
for (--array; PNT(out, ((x == 1) & 1)[fmts], *(array = ++array)), --x > 0;); /* These for loops are really neat!
I can do a bunch of things all in one line! Do something, test a conditional, do another thing! Or I can leave some of those
out, if I don't need them. */
for (;;) break; /* I can even do this! */
}main() {
int iarray[ARRAY_SIZE];
int x, y;
int ofs = iarray - &ofs; /* ofs is an offset */
void (*prnt_func)/* These comment things are pretty neat too. I can add annotations to my code, without having to hide them in variable names
or strings that do nothing. */(int*) = &print_array;
"Here's how I would have had to annotate code before. It's kind of a pain.";
srand((unsigned int)time(NULL));
x ^= x; /* ^= looks like a duck. I'm going to call it the "quack operator" */
for(;((y = rand/*om number generator*/(), x < /* I'm a comment in the middle of an expression */ARRAY_SIZE) && ((((x
= x + 1) - 1)[iarray] = /*number from 0 to 99*/(y - (y / 100) * 100)) || 1));); /* lot's of nested () there! */
PNT2LINES(out, Before sort, ---------------, \n);
for((*prnt_func)(&ofs+ofs),y^=y,x&=~x;(y+1>=ARRAY_SIZE&&(x&&!(y=x&=~x)))||y+1<ARRAY_SIZE;(++y,iarray[y]<(y-1)
[iarray])&&(y[iarray]^=iarray[y-1]^=iarray[y]^=*(iarray+y-1),x|=y)); /* This used to be two loops, when it was with GOTOs,
but I was able to
reduce it to one. That must be faster, right? It's also still easy to read, so it's a total win-win! */
/* That line had a lot of quack operators! */
PNT2LINES(out, After sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
} -
Wow! For loops are neat! I rewrote my code, got rid of the gotos, used for loops, and put in some comments like in the article you linked to. I think it's much improved now. I'm especially proud of my reduction of the number of loops. The main sorting part used to involve two nested loops (one inside the other), but I was able to reduce it to a single loop!
#include <stdlib.h>
#include <stdio.h>
#include <time.h>#define ARRAY_SIZE 20
#define PNT(s, l, a) fprintf(std##s, l, a)
#define PNT2LINES(s, l1, l2, e) PNT(s, #l1#e#l2#e, 0)void print_array(int *array) {
int x = ARRAY_SIZE;
char* fmts[] = { "%d, ", "%d\n" }; /* fmts has two strings in it */
for (--array; PNT(out, ((x == 1) & 1)[fmts], *(array = ++array)), --x > 0;); /* These for loops are really neat!
I can do a bunch of things all in one line! Do something, test a conditional, do another thing! Or I can leave some of those
out, if I don't need them. */
for (;;) break; /* I can even do this! */
}main() {
int iarray[ARRAY_SIZE];
int x, y;
int ofs = iarray - &ofs; /* ofs is an offset */
void (*prnt_func)/* These comment things are pretty neat too. I can add annotations to my code, without having to hide them in variable names
or strings that do nothing. */(int*) = &print_array;
"Here's how I would have had to annotate code before. It's kind of a pain.";
srand((unsigned int)time(NULL));
x ^= x; /* ^= looks like a duck. I'm going to call it the "quack operator" */
for(;((y = rand/*om number generator*/(), x < /* I'm a comment in the middle of an expression */ARRAY_SIZE) && ((((x
= x + 1) - 1)[iarray] = /*number from 0 to 99*/(y - (y / 100) * 100)) || 1));); /* lot's of nested () there! */
PNT2LINES(out, Before sort, ---------------, \n);
for((*prnt_func)(&ofs+ofs),y^=y,x&=~x;(y+1>=ARRAY_SIZE&&(x&&!(y=x&=~x)))||y+1<ARRAY_SIZE;(++y,iarray[y]<(y-1)
[iarray])&&(y[iarray]^=iarray[y-1]^=iarray[y]^=*(iarray+y-1),x|=y)); /* This used to be two loops, when it was with GOTOs,
but I was able to
reduce it to one. That must be faster, right? It's also still easy to read, so it's a total win-win! */
/* That line had a lot of quack operators! */
PNT2LINES(out, After sort, ---------------, \n);
(*prnt_func)(&ofs + ofs);
}SirTimothy wrote:
for((*prnt_func)(&ofs+ofs),y^=y,x&=~x;(y+1>=ARRAY_SIZE&&(x&&!(y=x&=~x)))||y+1
I checked it and it gives correct results. I't amazing. Especially, I don't get why
y[iarray]
does not cause SEGFAULT or something. Where the O(n^2) complexity is hidden? BTW. I had to implement all sorting algorithms as one of projets on my university. Bubble Sort was among them, but I did not care about performance so much.
void Bubble::Sort(Table &table, bool descending)
{
bool swapped;
int size = table.size();
int bound = size - 1;
int lastSwap = 0;
do {
swapped = false;
for (int i = 0; i < bound; i++)
{
TableElement t1 = table[i], t2 = table[i + 1];
if (descending ? t1 < t2 : t1 > t2) {
swap(table[i], table[i+1]);
swapped = true;
lastSwap = i;
}
}
bound = lastSwap;
} while (swapped);
}Greetings - Jacek
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SirTimothy wrote:
for((*prnt_func)(&ofs+ofs),y^=y,x&=~x;(y+1>=ARRAY_SIZE&&(x&&!(y=x&=~x)))||y+1
I checked it and it gives correct results. I't amazing. Especially, I don't get why
y[iarray]
does not cause SEGFAULT or something. Where the O(n^2) complexity is hidden? BTW. I had to implement all sorting algorithms as one of projets on my university. Bubble Sort was among them, but I did not care about performance so much.
void Bubble::Sort(Table &table, bool descending)
{
bool swapped;
int size = table.size();
int bound = size - 1;
int lastSwap = 0;
do {
swapped = false;
for (int i = 0; i < bound; i++)
{
TableElement t1 = table[i], t2 = table[i + 1];
if (descending ? t1 < t2 : t1 > t2) {
swap(table[i], table[i+1]);
swapped = true;
lastSwap = i;
}
}
bound = lastSwap;
} while (swapped);
}Greetings - Jacek
It is kinda amazing, isn't it? The
y[iarray]thing, I've seen in a few different websites, basically the compiler just expands it to*(y + iarray)which is the same asiarray[y]and it carries on its merry way. The O(n^2) complexity is hidden in the single loop, I reset the values of x and y in the conditional (they=x&=~xbit) when y gets past the array length and x is non-zero. Pretty near impossible to prove n^2 runtime, or to prove correctness, or even to prove that it terminates, but it's fun and it works. I thought about writing some more sorts like this, but haven't gotten to it... -
nah, just felt like doing it
We're not taking our meds now, are we?
Software Zen:
delete this;
Fold With Us![^] -
It is kinda amazing, isn't it? The
y[iarray]thing, I've seen in a few different websites, basically the compiler just expands it to*(y + iarray)which is the same asiarray[y]and it carries on its merry way. The O(n^2) complexity is hidden in the single loop, I reset the values of x and y in the conditional (they=x&=~xbit) when y gets past the array length and x is non-zero. Pretty near impossible to prove n^2 runtime, or to prove correctness, or even to prove that it terminates, but it's fun and it works. I thought about writing some more sorts like this, but haven't gotten to it...SirTimothy wrote:
the compiler just expands it to *(y + iarray) which is the same as iarray[y]
It relies on a C-specific feature, where size of
intis the same as size of an address, doesn't it? In C#intis always a 32-bit integer... I suppose proving n^2 runtime isn't hard. Each obfuscation can be transformated to a more readable form, which is fully equivalent. Step by step, one could get something similar to my code posted above. I suppose. Sometimes when I have a trouble with theory I generate a chart and write "The chart says, that the algorithm is quadratic, isn't it?". Unfortunately not every teacher was satisfied with such report... :rolleyes:Greetings - Jacek
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That, of course, is so that I can change the function name, and only need to change one place where it's used. Gotta think about maintainability and future modifications!
... maintainability and future modifications ... hahaha very funny! Can you tell us why you wrote this code? Are you a teacher showing "bad practice"? If one of my programmers would come up with a piece of code like this -> :thumbsdown:
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... maintainability and future modifications ... hahaha very funny! Can you tell us why you wrote this code? Are you a teacher showing "bad practice"? If one of my programmers would come up with a piece of code like this -> :thumbsdown:
Nah, not a teacher. Actually, just graduated from university. Why'd I write it? Bored, felt like taking some reasonably clean code and totally butchering it, thought I'd see how ugly I could make it :) Of course, it could be much worse, but whatever, it was fun!
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It is kinda amazing, isn't it? The
y[iarray]thing, I've seen in a few different websites, basically the compiler just expands it to*(y + iarray)which is the same asiarray[y]and it carries on its merry way. The O(n^2) complexity is hidden in the single loop, I reset the values of x and y in the conditional (they=x&=~xbit) when y gets past the array length and x is non-zero. Pretty near impossible to prove n^2 runtime, or to prove correctness, or even to prove that it terminates, but it's fun and it works. I thought about writing some more sorts like this, but haven't gotten to it...