Accessing information from nested struct passed to function - c

Question

I have the following code:
struct wordPair {
char* englishWord;
char* foreignWord;
};
struct dictionary {
struct wordPair ** data;
int nbwords;
int size;
};
Say I have struct dictionary *dictionaryPtr filled with some data, and I pass it to the following function:
char* dictionary_translate( struct dictionary* d,
const char* const english_word,
const char* const foreign_word)
Within the function dictionary_translate, how can I access the data from the struct wordPair that is nested within the passed struct? I need the function to return a strdup of either englishWord or foreignWord.
I was trying d->data->englishWord, but this gives me the error "request for member 'englishWord' in something not a structure or union".
UPDATE!
What I need the function dictionary_translate to do is determine if there is a matching word pair that contains one of the words passed to it, and return the strdup of the translation (the other word in the pair). Here is the array of words I have defined:
const char* test_translations[NB_TESTS][NB_COLS] =
{
{"hello", "hola"},
{"cat", "gato"},
{"dog", "perro"},
{"thanks", "gracias"},
{"pants", "pantalones"},
{"shoes", "zapatos"},
};
This is how I'm calling the function in the first test I'm trying, which is when the translate function is passed an English word and is required to return a foreign word:
char* translationPtr = NULL;
for (i = 0; i < NB_TESTS; i++) {
translationPtr = dictionary_translate(dictionaryPtr, test_translations[i][0], NULL);
printf("English Word %s translated: %s\n", test_translations[i][0], translationPtr);
}
Here is the translate function as I have it so far...
char* dictionary_translate( struct dictionary* d,
const char* const english_word,
const char* const foreign_word){
int i;
if (d == NULL) return NULL;
for (i = 0; i < d->nbwords; i++) {
if (strcmp(english_word, d->data[i]->englishWord) == 0)
return strdup(d->data[i]->foreignWord);
else if (strcmp(foreign_word, d->data[i]->foreignWord) == 0)
return strdup(d->data[i]->englishWord);
}
return NULL;
}
As soon as the program gets to the translation function, it crashes. I can't make sense of the debugger to find out what is going on, but it seems like translationPtr never has a value other than NULL (0x0). I'm new with the debugger, so I'm sure it could tell me more if I knew how to read it.

Answer 1

It isn't entirely clear what your function is to do, but about the simplest implementation that might legitimately work is:
#include <string.h>
struct wordPair
{
char *englishWord;
char *foreignWord;
};
struct dictionary
{
struct wordPair **data;
int nbwords;
int size;
};
extern char *dictionary_translate(struct dictionary *d,
const char *const english_word,
const char *const foreign_word);
char *dictionary_translate(struct dictionary *d,
const char *const english_word,
const char *const foreign_word)
{
for (int i = 0; i < d->nbwords; i++)
{
if (strcmp(english_word, d->data[i]->englishWord) == 0)
return strdup(d->data[i]->foreignWord);
else if (strcmp(foreign_word, d->data[i]->foreignWord) == 0)
return strdup(d->data[i]->englishWord);
}
return 0;
}
I think you should review the design of your struct dictionary. Using a double pointer seems unnecessary (or the reason for using it is not obvious). The only advantage is that you'd have a contiguous array of pointers to struct wordPair, while the actual struct wordPair elements need not be contiguously allocated themselves. The following code is a more orthodox definition, assuming that a contiguous array of struct wordPair is not a problem:
#include <string.h>
struct wordPair
{
char *englishWord;
char *foreignWord;
};
struct dictionary
{
struct wordPair *data;
int nbwords;
int size;
};
extern char *dictionary_translate(struct dictionary *d,
const char *const english_word,
const char *const foreign_word);
char *dictionary_translate(struct dictionary *d,
const char *const english_word,
const char *const foreign_word)
{
for (int i = 0; i < d->nbwords; i++)
{
if (strcmp(english_word, d->data[i].englishWord) == 0)
return strdup(d->data[i].foreignWord);
else if (strcmp(foreign_word, d->data[i].foreignWord) == 0)
return strdup(d->data[i].englishWord);
}
return 0;
}
Given the sample test code where one of the arguments to dictionary_translate() is a NULL pointer, the code in the function must be revised not to dereference the argument if it is null. This assumes the double-pointer version of struct dictionary.
char *dictionary_translate(struct dictionary *d,
const char *const english_word,
const char *const foreign_word)
{
for (int i = 0; i < d->nbwords; i++)
{
if (englishWord != NULL && strcmp(english_word, d->data[i]->englishWord) == 0)
return strdup(d->data[i]->foreignWord);
else if (foreignWord != NULL && strcmp(foreign_word, d->data[i]->foreignWord) == 0)
return strdup(d->data[i]->englishWord);
}
return 0;
}

Answer 2

d->(*data)->englishWord
Should compile.