Some pointer stuff

p.c

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

struct person {
	char nname[20];
	char vname[20];
};

int main()
{
	char str[] = "Foo bar lich";
	char *poi;

	poi = &str[0]; // or: poi = str;

	printf("%s\n", str);
	printf("%s\n", poi);
	printf("%c\n", *poi);

	while (*poi != '\0') {
		printf("%c\n", *poi);
		poi++;
	}

	//

	int zahl = 1;
	char *poi1 = &zahl;

	//TODO(d630)
	*poi1 = *poi1 + 459999;
	printf("%d %d\n", zahl, *poi1);
	*poi1 = 1 + 459999;
	printf("%d %d\n", zahl, *poi1);

	//

	struct person p;

	strcpy(p.nname, "n");
	strcpy(p.vname, "v");
	printf("%s %s\n", p.nname, p.vname);

	struct person *ptr = &p;
	printf("%s %s\n", ptr->nname, ptr->vname);

	//

	strcpy(ptr->vname, "hugo");
	strcpy(ptr->nname, "l");
	printf("%s %s\n", ptr->nname, ptr->vname);

	return 0;
}

// vim: set ft=c :

pointer.c

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

void
test_case(char *str)
{
	while (*str != '\0') {
		if (*str >= 65 && *str <= 90)
			printf("%c upper-case letter\n", *str);
		else if (*str >= 97 && *str <= 122)
			printf("%c lower-case letter\n", *str);
		str++;
	}
}

void
test_rename(char *str, char c1, char c2)
{
	while (*str != '\0') {
		if (*str == c1)
			*str = c2;
		str++;
	}
}

char *
test_cut(char *str, char c)
{
	while (*str != '\0') {
		if (*str == c)
			break;
		str++;
	}

	return str;
}

void
test_fill(int *arr, int l, int j)
{
	for (int i = 0; i < l; i++)
		arr[i] = j++;
}

void
test_print(int *arr, int len)
{
	for (int i = 0; i < len; i++)
		printf("%d %d\n", i, arr[i]);
}

int
main()
{
	char str[] = "Hello_World!";

	printf("old: <%s\n>", str);
	test_rename(str, '_', ' ');
	printf("new: <%s\n>", str);

	test_case(str);

	printf("<%s>\n", test_cut(str, 'W'));
	printf("<%s>\n", test_cut(str, '_'));

	// ---

	int iarr[6] = {0};
	int len =  sizeof(iarr)/sizeof(iarr[0]);

	test_print(iarr, len);
	test_fill(iarr, len, 1);
	test_print(iarr, len);

	return 0;
}

// vim: set ft=c :

gcc -g -O2 -std=c99 -Wall -Wextra -Wwrite-strings -o pointer pointer.c && chmod +x ./pointer && ./pointer