Questions 10

1. Where exactly are the files gsl_multimin.h and gsl_multiroots.h located in your box?

   Hint: gsl-config --cflags.

2. Consider a Makefile,

   blahblah : data log ; for f in $^; do echo -n $$f:; cat $$f; done
   data log : Makefile ; echo $@ > $@
   clean    :          ; $(RM) data log
   

   What (and why) will it do and what (and why) will it build? Why double dollars in the first line? Why echo -n ?
3. Suppose you run the command make main and it fails with diagnostics

   cc     main.c   -o main
   main.c:1:19: fatal error: gsl_sf.h: No such file or directory
   compilation terminated.
   

   Explain the error and how to correct it.

   Hint: clang returns the following diagnostics,

   clang     main.c   -o main
   main.c:1:9: fatal error: 'gsl_sf.h' file not found
   #include<gsl_sf.h>
           ^
   1 error generated.
   

4. Suppose you run the command make main and it fails with diagnostics

   cc     main.c   -o main
   /tmp/cce2r3LL.o: In function `main':
   main.c:(.text+0x1e): undefined reference to `gsl_sf_gamma'
   collect2: error: ld returned 1 exit status
   

   Explain the error and how to correct it. Who is ld that returned exit status 1?
5. Will this definition of f work (and why)?

   #include"stdio.h"
   #include"math.h"
   int main(){
   	double A=3.5, T=3.2, B=1.2;
   	#define f(x) A*exp(-(x)/T)+B
   	for(double t=0;t<=5;t+=1) printf("%g %g\n",t,f(t));
   return 0;
   }
   

6. Will this definition of f work (and why)?

   #include"stdio.h"
   #include"math.h"
   int main(){
   	double A=3.5, T=3.2, B=1.2;
   	double f(double x){return  A*exp(-x/T)+B;}
   	for(double t=0;t<=5;t+=1) printf("%g %g\n",t,f(t));
   return 0;
   }
   

7. Will this definition of f work (and why)?

   #include"stdio.h"
   #include"math.h"
   #define f(x) A*exp(-(x)/T)+B
   int main(){
   	double A=3.5, T=3.2, B=1.2;
   	for(double t=0;t<=5;t+=0.1) printf("%g %g\n",t,f(t));
   return 0;
   }
   

8. Will this definition of f work (and why)?

   #include"stdio.h"
   #include"math.h"
   double f(double x){return  A*exp(-x/T)+B;}
   int main(){
   	double A=3.5, T=3.2, B=1.2;
   	for(double t=0;t<=5;t+=1) printf("%g %g\n",t,f(t));
   return 0;
   }
   

9. Will this call to print_f_of_one work (and why)?

   #include"stdio.h"
   void print_f_of_one( double (*f)(double) ){printf("%g\n",f(1.0));}
   int main(){
   	double f(double x){return x+x;}
   	print_f_of_one(f);
   return 0;
   }
   

10. Will this call to print_f_of_one work (and why)?

    #include"stdio.h"
    void print_f_of_one( double (*f)(double) ){printf("%g\n",f(1.0));}
    int main(){
    	#define f(x) (x)+(x)
    	print_f_of_one(f);
    return 0;
    }
    

11. Explain the difference between

    echo 'gsl-config --libs'
    

    and

    echo `gsl-config --libs`
    

12. Write a C-program that sends its command-line arguments to the standard output (that is, emulates the echo unix utility).