Thread: Number of elements in multiarray

I'm trying to determine the number of elements in a multiarray; The approach I've been trying to use so far is:

Code:

sizeof(multi_arr) / sizeof(multi_arr[0])

but sizeof(multi_arr) seems to be returning the size of the individual components.

Anyone know of a different approach i could use?

Here's the program I'm currently working on:

Code:

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

enum weekday { sun = 1, mon, tue, wed, thu, fri, sat};
typedef enum weekday weekday;

struct team{
  char shortName[4];
  char longName[30];
  int homeWins;
  int homeLoses;
  int homeDraws;
  int homeGoalsFor;
  int homeGoalsAgainst;
  int awayWins;
  int awayLoses;
  int awayDraws;
  int awayGoalsFor;
  int awayGoalsAgainst;
};typedef struct team team;

struct match{
  int round;
  weekday day;
  int time;
  char homeTeam[4];
  char awayTeam[4];
  int homeGoals;
  int awayGoals;
};typedef struct match match;

team make_team(const char shortName[4], const char longName[30]);
team *make_league(const char *shortNames[4], const char *longNames[30]);
void add_teams(const char *shortNames[4], const char *longNames[30], team *league);
team *make_superliga(void);

team *make_superliga(void){
  char shortNames[12][4] = {"FCN", "FCK", "FCM", "EFB", "SE",  "RFC",
			    "HBK", "SIF", "BIF", "OB",  "AGF", "AAB"};

  char longNames[12][30] = {"FC Nordsjælland"         , "F.C. København"      ,
			    "FC Midtjylland"          , "Esbjerg fB"          ,
			    "Sønderjyske"             , "Randers FC"          ,
			    "HB Køge"                 , "Silkeborg IF"        ,
			    "Brøndby IF"              , "Odense Boldklub"     ,
			    "Aarhus Gymnastikforening", "Aalborg Boldspilklub"};
  return make_league(shortNames, longNames);
}

void add_teams(const char *shortNames[4], const char *longNames[30], team *league){
  static int thisTeam = 0;
  if(thisTeam == (sizeof(league) / sizeof(team))){
    thisTeam = 0;
    return;
  }
  else if(thisTeam > (sizeof(league) / sizeof(team))){
    league[thisTeam] = make_team(shortNames[thisTeam], longNames[thisTeam]);
    thisTeam++;
  }
  else{
    printf("Should not happen ... bye!");
    exit(-1);
  }
}

team *make_league(const char *shortNames[4], const char *longNames[30]){
  team *league;
  league = malloc(sizeof(team) * (sizeof(shortNames) / sizeof(shortNames[0])));
  add_teams(shortNames, longNames, league);
  return league;
}

team make_team(const char shortName[4], const char longName[30]){
  team result;
  strcpy(result.shortName, shortName);
  strcpy(result.longName, longName);
  result.homeWins = 0;
  result.homeLoses = 0;
  result.homeDraws = 0;
  result.homeGoalsFor = 0;
  result.homeGoalsAgainst = 0;
  result.awayWins = 0;
  result.awayLoses = 0;
  result.awayDraws = 0;
  result.awayGoalsFor = 0;
  result.awayGoalsAgainst = 0;
  return result;
}

int main(void){
  team *superliga;
  superliga = make_superliga();
  printf("%s\n", superliga[1].longName);
  return 0;
}

where the interesting part is in the function make_league, when i try to allocate space for a league of teams

Question 6.21

Thanks, that solved the problem.

C treats the following definitions the same (sad but true).

Code:

int foo(int bar[10]);
int foo(int bar[]);
int foo(int *bar);

therefore sizeof bar is always the size of a single pointer (4 on most 32 bit machines).

I think the compiler should warn about the first definition, as there is unused and therefore misleading information in the prototype, but compilers don't seem to care what I'm thinking.

I was just thinking... perhaps the compiler does look at the array size in the prototype/header. But not for the example you've given. What about

Code:

int foo(int bar[][10]);

In that case inside the function the compiler knows what the width of the array is while calculating row offsets. I haven't tested this but it seems reasonable. Still, any number in the FIRST axis, if present, is always ignored.