The h Bar

12:09 AM

tikz is terrible

12:46 AM

@dmckee Thanks. I guess what prompted the question is I feel a general need to learn a new tool, so I am looking for advice on a few to look into before I take the plunge. Right now I just use gnuplot for graphs and hand-drawn stuff for everything else, but between teaching classes, writing papers and sketching out some designs for my peers, I feel the need for a way to produce some more professional looking diagrams.

Since I've seen some nice diagrams on SE, I was wondering if there was any local consensus on which tool or tools were the "best".

dmckee

1:21 AM

Nothing wrong with gnuplot for graphs, but I don't have a great suggestion for drawing other figures. If you see a user that consistently posts good figures (and we have a few) you could ask them what they use (chat would be better than a comment).

vzn

@NeuroFuzzy =D thx much man! think posted links are mostly on physics. like your blog & (new?) youtube channel too wink =D mathandcode.com/programs m.youtube.com/user/DKM101 so still wanna do an upcoming talk? its all clear for you right now

@0ßelö7 ?!? thought you werent into that stuff o_O

David Z

3:32 AM

@NeuroFuzzy cc @vzn I actually wasn't following that particular discussion too closely, but in general, 50 links in 250 days all to your own content is a bit much.

@dmckee hey! TikZ syntax is actually pretty clear

vzn

4:04 AM

@DavidZ its mostly wrt physics. there are apparently no official SE guidelines on so-called "self-promotion". ps why do you never link to your own blog? (maybe have cited it myself here more than you have!) seems like a glaring omission. is every citation to a personal blog "self-promotion"? dont want to be tarred with a brush. :( O_o

David Z

4:22 AM

There is one, but it's intentionally vague

I don't link to my own blog because it's very rare that there is something on there worth linking to

And I'm not sure what the rest of your message is getting at, but surely you know better than to think that linking to someone else's blog counts as self-promotion?

vzn

5:08 AM

@DavidZ the guidelines are for main SE sites, not really chat, which is purposely quite loose(r). less than 1% of my chat msgs link to my blog, probably a small fraction of a percent, typically tied in with current discussions/ topics/ responses. (just wondering, if nothing in your blog is worth linking to here in chat, why do you write it? ok, rhetorical question, guess there could still be good reasons.)

rob

@simplicio Current favorite tool: matplotlib. I especially like the ipython command shell, which has some nice syntactical sugar.

Koolman

Can I use

area = double pow(double side, double 2);

rob

@simplicio An example output by me

Koolman

in C programming

to write $side^2$

John Rennie

@Koolman Brackets round the casts

Koolman

5:18 AM

area = (double) pow(double side, double 2);

like this

John Rennie

Anyway why would you do that? Why not side*side

area = pow(side, 2)

Koolman

I want to learn how to use it

the power function

John Rennie

You shouldn't need the casts

Koolman

tutorialspoint.com/c_standard_library/c_function_pow.htm

in description it is given like that

John Rennie

The function definition is double pow(double x, double y)

Koolman

5:20 AM

@JohnRennie will there be no semicolon

John Rennie

If you're calling it just use area = pow(side, 2);

Koolman

then when we have to use double pow(double x, double y)

John Rennie

That's the function prototype

Anonymous

@Koolman You need to declare side as a double variable before writing that statement. Also, you need to assign a value to side.

John Rennie

You only have to use the prototype if you're writing a header file

Koolman

5:21 AM

#include<stdio.h>
#include<stdlib.h>
#include<math.h>

int main()
{
double side,area;
printf("enter the side of a square : ");
scanf("%lf",&side);
area = double pow(double side, double 2);
printf("Area of the square : %lf",area);
printf("Area of square in integer form : %d",(int)area);

return 0;
}

John Rennie

area = pow(side, 2);

Anonymous

@Koolman Change that to area=pow(side,2)

Anonymous

That's all

John Rennie

Try it if you don't believe me :-)

Anonymous

You have already taken side as input

rob

5:23 AM

@Koolman Have you tried that? The compiler should give an error message.

Koolman

I have already tried that

rob

@Koolman Did it work?

Koolman

It is showing

/tmp/ccY7he4N.o: In function `main':
areasq.c:(.text+0x56): undefined reference to `pow'
collect2: error: ld returned 1 exit status

@rob no

Anonymous

@Koolman Of course. Writing double pow makes no sense

rob

@Koolman To your compiler options, add "-lm" to link the math library.

Secret

5:24 AM

Claim: Thermodynamics in a nutshell:

rob

You have it included, but not linked.

Koolman

@Blue I have not written that

rob

But you should then get some syntax issue, because the relevant line in your program need be only area = pow(side, 2)

Anonymous

@Koolman You have area = double pow(double side, double 2);

Anonymous

^ Change that to area=pow(side,2);

Koolman

5:25 AM

@rob Sorry , but I don't know how to use it

rob

@Koolman How do you compile?

Koolman

@Blue area=pow(side,2) after using this

Secret

A system with uneven distribution of entropy trying to equalise itself, and in doing so, part of it can be converted to useful work

Koolman

I got that error

@rob I am using terminal

Ubuntu

rob

@Koolman You're typing something like gcc blah.c?

Koolman

5:27 AM

yeah

rob

@Koolman Change to gcc -lm blah.c

Keep all your other options

If you have any, that is

Koolman

-lm areasq.c
No command '-lm' found, did you mean:
Command 'plm' from package 'plm' (universe)
Command 'clm' from package 'mcl' (universe)
-lm: command not found

Secret

One reason of having this suspicion is that notice how in all devices we use to generate energy, it almost always involve some kind of gradient between two or more ends, and as work is being extracted, the gradient slowly vanishes

Anonymous

Here's the corrected code:

Anonymous

#include<stdio.h>
#include<math.h>
int main()
{
double side,area;
printf("Enter the side of a square : ");
scanf("%f",&side);
area =pow(side,2);
printf("Area of the square : %f",area);
printf("Area of square in integer form : %d",(int)area);

return 0;
}

rob

5:28 AM

@Koolman No, continue to run the program gcc with the argument blah.c (or whatever)

But add the additional argument -lm.

Anonymous

codechef.com/ide

Anonymous

Execute the code on the online IDE to check

Anonymous

If it is not working on your system that's some compiler issue

Koolman

@rob additional argument ??

@Blue should we not use %lf

19

Q: Scanf/Printf double variable C

Let's say I have this following bit of code in C: double var; scanf("%lf", &var); printf("%lf", var); printf("%f", var); It reads from stdin variable 'var' and then prints twice in stdout 'var'. I understand that's how you read a double variable from stdin, but my questions are: 1. Why can you...

rob

@Koolman At the terminal prompt $, where you would usually type gcc blah.c ...

@Koolman ... instead type gcc -lm blah.c

Anonymous

5:31 AM

@Koolman Both will work

Anonymous

But yes, lf should be the one used over here

Koolman

gcc -lm areasq.c
/tmp/cc2kCIOy.o: In function `main':
areasq.c:(.text+0x56): undefined reference to `pow'
collect2: error: ld returned 1 exit status

rob

@Koolman Hmm. Give me a minute.

Anonymous

34

Q: Undefined reference to pow( ) in C, despite including math.h

Possible Duplicate: Problem using pow() in C what is 'undefined reference to `pow'' I'm having a bit of an issue with a simple piece of coursework for uni that's really puzzling me. Essentially, I've to write a program that, amongst other things, calculates the volume of a sphere fr...

c

Anonymous

3

Q: What does "collect2: error: ld returned 1 exit status" mean?

I see the error collect2: error: ld returned 1 exit status very often. For example, I was executing the following snippet of code: void main() { char i; printf("ENTER i"); scanf("%c",&i); clrscr(); switch(i) { default: printf("\nHi..\n"); break; case 1: pri...

c compiler-errors

Koolman

5:34 AM

#include<stdio.h>
#include<stdlib.h>
#include<math.h>

int main()
{
double side,area;
printf("enter the side of a square : ");
scanf("%lf",&side);
area =pow(side,2);
printf("Area of the square : %lf",area);
printf("Area of square in integer form : %d",(int)area);

return 0;
}

it is showing

gcc areasq.c
/tmp/ccciKePE.o: In function `main':
areasq.c:(.text+0x56): undefined reference to `pow'
collect2: error: ld returned 1 exit status

Anonymous

gcc -o areasq areasq.c -lm

Anonymous

@Koolman Try this once^

Koolman

koolman@ubuntu:~/s$ gcc -o areasq areasq.c -lm
koolman@ubuntu:~/s$ ./a.out
bash: ./a.out: No such file or directory

John Rennie

./areasq

rob

@Koolman So -o changes the name of the output file. Try ./areasq

Koolman

5:42 AM

finally done

huh

Now please anybody can explain what we have done

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