code Newbie Question. Seriously lol.

[buffered]

hey guys. wanna take this chance to say hi as well to all of you.

just took up a programming module without ANY programming knowledge and unfortunately this basic programming module is being taught by a lecturer from China. not a single soul in the lecture knows what he's mumbling about.

hoping to learn from u guys here.

We use Vi in our labs. i could use the command gcc in there but couldnt use in in Vim when im home.[ running xp]. well the lab looked like it was using windows xp as well.. weird.

Heres qn 1 which i hope u guys could guide me.

Qn 1. Write a program to approx. the derivative of f(x) = x^2 +0.5x+1 using the half-increment method, in which the derivative of f(x) at a point c is approx by [f(c+h/2) - f(c-h/2)]/h, for small h<0.1. the program takes the values of c and small h from command line and then displays the approx of the derivative of f(x) at c.

here's my coding:

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

double f(double x) {
       return x*x+0.5*x+1;}
       
int main(int argc, char *argv[])
       {
           double c,h,ans;
           
           c=atof(argv[1]);
           h=atof(argv[2]);
           
           ans= (f(c+h)/2 - f(c-h)/2)/h ;
           
           printf(" %.3f", ans);
           
           return(0);
}

compiled it successfully. tried to open with ms-dos. gave an error. is there anything wrong with it guys? thanks a mill

and oh, can anyone tell me why we must put a double x in double f(double x)?

thx!

[redhead]

Hi Buffered, and welcome here at CN

tried to open with ms-dos. gave an error.

You my friend have had your first encounter with the famous Unix/Dos LF/CR indifferencies

can anyone tell me why we must put a double x in double f(double x)?

Because otherwise

0.5*x

would return a warning telling one a conversion choice would have to be made, and depending on the compilers skills it could end up as either

0*x

or

1*x

which isn't the behaviour youre looking for, read about Floats vs. integers

If you want to use the same at home as you use on campus, there is mingW which provides Unix like tools for windows aswell as VI for windows

How ever, given that you most likely would delve further into teh usage of a Unix like system, I would suggest you try a Unix like environment like installing Linux under windows

[buffered]

thank you so much for ur reply! i'll be reading the links you've provided me with!

turly appreciate it!

[landonmkelsey]

super easy is LaGrangian interpolation

collocation=approximation passes through given points (x(n) y(n) ) n= 0,1,2

y(x) =

y(0)* (x(1) -x) *(x(2)-x)/(x(1)-x(0)*x(2)-x(0)) + (this term = y(0) at x = x(0)

y(1)*(x(0) -x) *(x(2)-x)/(x(0)-x(1)*x(2)-x(1)) + (this term = y(1) at x = x(1)


y(2)*(x(0) -x) *(x(1)-x)/(x(0)-x(2)*x(1)-x(2)) + (this term = y(2) at x = x(2)

ends up being a parabola

[buffered]

#include <stdio.h>
#include <string.h>

int main(int argc, char*argv[]){

int January_first_day,February_first_day,March_first_d ay,April_first_day,May_first_day,June_first_day,Ju ly_first_day,August_first_day,September_first_day, October_first_day,November_first_day,December_firs t_day;

int i,j,k,l,m,n,o,p,q,r,s,t;

printf("\n January");
printf(" Sun Mon Tue Wed Thu Fri Sat\n");

if (strcmp(argv[1], "Sun") == 0) January_first_day=6; if (strcmp(argv[1], "Mon") == 0) January_first_day=7;
if (strcmp(argv[1], "Tue") == 0) January_first_day=1; if (strcmp(argv[1], "Wed" )== 0) January_first_day=2;
if (strcmp(argv[1], "Thu") == 0) January_first_day=3; if (strcmp(argv[1], "Fri") == 0) January_first_day=4;
if (strcmp(argv[1], "Sat") == 0) January_first_day=5;
for (i = 1; i<=6*January_first_day-2; i = i+1) { printf(" ");} /* print out the first day */
printf("%2d", 1);

for (i=2; i<= 31; i=i+1) {
if ( (i+January_first_day-2)%7 == 0) printf("\n"); /* finish one week */
printf(" %2d ", i); /* insert 4 spaces for format purpose */
}


printf("\n February");
printf(" Sun Mon Tue Wed Thu Fri Sat\n");

if (strcmp(argv[1], "Sun") == 0) February_first_day=3; if (strcmp(argv[1], "Mon") == 0) February_first_day=4;
if (strcmp(argv[1], "Tue") == 0) February_first_day=5; if (strcmp(argv[1], "Wed")== 0) February_first_day=6;
if (strcmp(argv[1], "Thu") == 0) February_first_day=7; if (strcmp(argv[1], "Fri") == 0) February_first_day=1;
if (strcmp(argv[1], "Sat") == 0) February_first_day=2;
for (j = 1; j<=6*February_first_day-2; j = j+1) { printf(" ");} /* print out the first day */
printf("%2d", 1);

for (j=2; j<= 29; j=j+1) {
if ( (j+February_first_day-2)%7 == 0) printf("\n"); /* finish one week */
printf(" %2d", j); /* insert 4 spaces for format purpose */
}

comes out

January Sun Mon Tue Wed Thu Fri Sat
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
February Sun Mon Tue Wed Thu Fri Sat
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29

the 1st of every month is out of position lol. any idea why. spent the last 6 hrs. its hurting my eyes more then when im cutting onions for my mom.

thx u guys!

[buffered]

umm dunno why it showed up that way, but take it the rest of the dates except the first are out of sync with the rest, hiding away at the left corner

[landonmkelsey]

clutter can make programs unmanageable

simplicity make programs easier to debug/change

modularity

would help to add a statement stating what the code is trying to do!

pseudo code is a sort of textual flow chart

[landonmkelsey]

add a switch statement to eliminate those "strcmp" statements