C programming "weird output"

Question

I'm trying to make a function that given a string, it processes the string like I show below, modifying the value of a struct variable. In simple language, given a string, it modifies the coordinates of a variable.

typedef struct coo {
    int x;
    int y;
} Coord;

typedef struct exer{
    char ray[1000];
    Coord coords[1000];
} exercise;

exercise test;

int coordinates(char *sent){

    int i=0,j=1;
    test.coords[0].x=0;
    test.coords[0].y=0;

    if(strlen(test.ray)>=strlen(sent)){
        for(;((int) strlen (test.ray) >= j && sent[i]!='\0');i++){
            if(sent[i]=='F'){test.coords[j].x = test.coords[j-1].x+1; 
                test.coords[j].y = test.coords[j-1].y;} else{
                    if(sent[i]=='L'){test.coords[j].y = test.coords[j-1].y+1; 
                        test.coords[j].x = test.coords[j-1].x;} else{
                            if(sent[i]=='R'){test.coords[j].y = test.coords[j-1].y-1; 
                                test.coords[j].x = test.coords[j-1].x;} else{
                                    return erromsg(SENT);}
                        }
                }
            j++;
        }
        for(;(int) strlen (test.ray) > i && sent[i]=='\0';){
            for(;j<(int) strlen(test.ray);j++){
                test.coords[j].x = test.coords[j-1].x+1;
                test.coords[j].y = test.coords[j-1].y;
            }
        }
    }
    else return errormsg(SENT);
    return 1;
}

The problem is that when I later call a function to show the output on the screen, it gives me coordinates with characters like this: � and others who won't even copy to this page :) I'm new to C, so any advice will be welcome.

edit: code to print the coordinates

int showcoords(){

    int k=0;
    if(test.coords==NULL) return errormsg(COLOC); else{
        while((int) strlen (test.ray)>k){
            printf("(%c,%c) ",test.coords[k].x,test.coords[k].y);
            k++;
        }
    }
    printf("\n");
    return 1;
}

What is the value of sent? How do you output the coordinates? — Some programmer dude
– Some programmer dude, Commented Mar 23, 2013 at 15:43
sent is just an array with the char's F, L, or R. I output the coordinates with another function that print's them one by one with "(%c,%c)" — PablodeAcero
– PablodeAcero, Commented Mar 23, 2013 at 15:46
Print coordinates with %d since they are int not char. — user1944441
– user1944441, Commented Mar 23, 2013 at 15:47
The expression test.coords==NULL will always be false. An array can never be NULL. — Some programmer dude
– Some programmer dude, Commented Mar 23, 2013 at 16:25

Dave · Accepted Answer · 2013-03-23 15:55:08Z

1

printf's %c specifier means print the corresponding character, so 100 -> d, etc. Since your numbers aren't anything to do with ASCII/Unicode, you get seemingly random characters.

Simply change %c for %d, which prints integer numbers. There are many other flags, such as %f for floats and doubles. You can also apply formatting such as leading zeroes, etc.

See this handy reference: http://www.cplusplus.com/reference/cstdio/fprintf/

answered Mar 23, 2013 at 15:55

Dave

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