[Structures de données] Accès à l'élément suivant d'un menu

Version imprimable

Bonjour,

pour représenter un menu, j'ai proposé la structure suivante :

Code:

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typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;

Voici le menu de mon exemple :
http://gensiteweb.1s.fr/uploaded_fil...u_next_sub.png

Le problème qui se pose est lorsque j'essaye de récupérer l'élément suivant de 'Options' (c'est à dire 'Exit').
Ma fonction nextMenu semble échouer :

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$ ./a.out 2>/dev/null
main: call menuNext on label 'Play'
main: label is now 'Options'
main: call menuNext on label 'Options'
main: label is now 'TVï¿'
main: call menuNext on label 'TVï¿'
main: label is now 'TVï¿'

Voici le code complet :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(2 * sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if(menu->label==label){
		fprintf(stderr, "\tmenuNext: label '%s' found\n", menu->label);
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu->next);
		}
		else{
			fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu);
		}
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			menuNext(menu->sub, label);
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			menuNext(menu->next, label);
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
}
 
/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		NULL
	);
	menu_current=menu1;
 
	/* Call menuNext 3 times */
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
 
	return(0);
}

Qui peut m'expliquer pourquoi je n'obtiens pas 'Exit'?

Merci beaucoup.

13/06/2009, 10h13
Lucien63

Code:

if(menu->label==label){

C'est comme celà que tu compare des chaines de caractères ?

Ah oui bien vu :)

Voici la correction donc :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(2 * sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if(strcmp(menu->label, label) == 0){
		fprintf(stderr, "\tmenuNext: label '%s' found\n", menu->label);
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu->next);
		}
		else{
			fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu);
		}
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			menuNext(menu->sub, label);
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			menuNext(menu->next, label);
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
}
 
/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		NULL
	);
	menu_current=menu1;
 
	/* Call menuNext 3 times */
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
 
	return(0);
}

Pourtant le programme réagit toujours de la même façon :

Code:

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$ ./a.out 2>/dev/null
main: call menuNext on label 'Play'
main: label is now 'Options'
main: call menuNext on label 'Options'
main: label is now 't¿'
main: call menuNext on label 't¿'
main: label is now 't¿'

Pourquoi ne parvient t'il pas à passer à l'élément suivant de 'Options'?

13/06/2009, 13h30
diogene

Pourquoi la fonction menuNext() ne renvoie t-elle rien lorsqu'on passe par le else du if(strcmp(menu->label, label) == 0)... et pourquoi les valeurs de retour des appels récursifs à menuNext() sont-elles ignorées ?

C'est vrai, il me semble que quelques return ont été oubliés :)

Voici la correction :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(2 * sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if(strcmp(menu->label, label) == 0){
		fprintf(stderr, "\tmenuNext: label '%s' found\n", menu->label);
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu->next);
		}
		else{
			fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu);
		}
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			return(menuNext(menu->sub, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			return(menuNext(menu->next, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
}
 
/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		NULL
	);
	menu_current=menu1;
 
	/* Call menuNext 3 times */
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
	printf("main: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label);
 
	return(0);
}

Le résultat me satisfait :

Code:

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$ ./a.out 2>/dev/null
main: call menuNext on label 'Play'
main: label is now 'Options'
main: call menuNext on label 'Options'
main: label is now 'Exit'
main: call menuNext on label 'Exit'
main: label is now ' `õù6þ6þ¿86þ¿ ùê·Àôù·`õù6þ6þ¿X6þ¿8P`õù6þ6þ¿x6þ¿Ph`õù6þ6þ¿6þ¿hÄ6þ¿ôïù·àLþ·'

Je pense aussi que j'ai commis une boulette sur l'allocation mémoire :

Code:

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menu = malloc(2 * sizeof(Menu));

Devrait être :

Code:

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menu = malloc(sizeof(Menu));

tout simplement.
Pas vrai?

13/06/2009, 15h02
diogene

Citation:

Pas vrai?

Si évidemment !

Ok dans ce cas une petite correction s'impose :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if(strcmp(menu->label, label) == 0){
		fprintf(stderr, "\tmenuNext: label '%s' found\n", menu->label);
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu->next);
		}
		else{
			fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu);
		}
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			return(menuNext(menu->sub, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			return(menuNext(menu->next, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
}
 
/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		NULL
	);
	menu_current=menu1;
 
	/* Call menuNext on 'Play' */
	printf("\nmain: call menuNext on label '%s'\n", "Play\0");
	menu_current=menuNext(menu1, "Play\0");
	printf("main: label is now '%s'\n", menu_current->label); /* Options */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Exit */
 
	/* Call menuNext when there isn't a next */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Exit */
 
	/* Call menuNext on 'Video' */
	printf("\nmain: call menuNext on label '%s'\n", "Video\0");
	menu_current=menuNext(menu1, "Video\0");
	printf("main: label is now '%s'\n", menu_current->label); /* Audio */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Control */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Game */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Back */
 
	/* Call menuNext when there isn't a next */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Back */
 
	return(0);
}

Voici le résultat :

Code:

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$ ./a.out 2>/dev/null
 
main: call menuNext on label 'Play'
main: label is now 'Options'
 
main: call menuNext on label 'Options'
main: label is now 'Exit'
 
main: call menuNext on label 'Exit'
main: label is now '▒`E
ž▒¡®¿▒¡®¿H¡®¿▒Iû·ÀD
ž`E
ž▒¡®¿▒¡®¿h¡®¿(X8`E
ž▒¡®¿▒¡®¿¡®¿8XH`E
ž▒¡®¿▒¡®¿š¡®¿HXhÔ¡®¿ô?
žàž'
 
main: call menuNext on label 'Video'
main: label is now 'Audio'
 
main: call menuNext on label 'Audio'
main: label is now 'Control'
 
main: call menuNext on label 'Control'
main: label is now 'Game'
 
main: call menuNext on label 'Game'
main: label is now 'Back'
 
main: call menuNext on label 'Back'
main: label is now 'Back'

J'ai ajouté tous les cas de tests possibles pour l'appel de la fonction menuNext. Sur 8 cas, 1 pose problème, celui lorsque j'essaye d'avoir le suivant de 'Exit' alors qu'il n'y en a pas :

Code:

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main: call menuNext on label 'Exit'
main: label is now '▒`E
ž▒¡®¿▒¡®¿H¡®¿▒Iû·ÀD
ž`E
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Le programme était sensé me renvoyer 'Exit' étant donné que le suivant de 'Exit' n'existe pas.
Il a pourtant bien réussi à le faire pour 'Back' étant donné que le suivant de 'Back' n'existe pas, il m'a retourné 'Back'.

Pourquoi ne parvient-t-il pas à me retourner le suivant de 'Exit'?

La fonction menuNext() a encore la possibilité de sortir sans renvoyer une valeur :

Code:

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Menu* menuNext(Menu *menu, char* label){
...
	if(strcmp(menu->label, label) == 0){...
	else{
		/* if it has a sub */
		if(menu->sub != NULL){...
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){...
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
/***********************************************************
 On peut arriver ici : si menu->sub == NULL et menu->next == NULL et pas de return ....
************************************************************/
}

Sérieux il faut avoir l'œil partout :)
Je te remercie beaucoup.

Voici la correction :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next; /* the next item */
	struct menu *sub; /* the sub menu */
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if(strcmp(menu->label, label) == 0){
		fprintf(stderr, "\tmenuNext: label '%s' found\n", menu->label);
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu->next);
		}
		else{
			fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
			fprintf(stderr, "menuNext: end\n");
			return(menu);
		}
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			return(menuNext(menu->sub, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			return(menuNext(menu->next, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
		fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
		return(menu);
	}
}
 
/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		NULL
	);
	menu_current=menu1;
 
	/* Call menuNext on 'Play' */
	printf("\nmain: call menuNext on label '%s'\n", "Play\0");
	menu_current=menuNext(menu1, "Play\0");
	printf("main: label is now '%s'\n", menu_current->label); /* Options */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Exit */
 
	/* Call menuNext when there isn't a next */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Exit */
 
	/* Call menuNext on 'Video' */
	printf("\nmain: call menuNext on label '%s'\n", "Video\0");
	menu_current=menuNext(menu1, "Video\0");
	printf("main: label is now '%s'\n", menu_current->label); /* Audio */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Control */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Game */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Back */
 
	/* Call menuNext when there isn't a next */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Back */
 
	return(0);
}

Et le résultat :

Code:

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$ ./a.out 2>/dev/null
 
main: call menuNext on label 'Play'
main: label is now 'Options'
 
main: call menuNext on label 'Options'
main: label is now 'Exit'
 
main: call menuNext on label 'Exit'
main: label is now 'Back'
 
main: call menuNext on label 'Video'
main: label is now 'Audio'
 
main: call menuNext on label 'Audio'
main: label is now 'Control'
 
main: call menuNext on label 'Control'
main: label is now 'Game'
 
main: call menuNext on label 'Game'
main: label is now 'Back'
 
main: call menuNext on label 'Back'
main: label is now 'Back'

Cette fois la fonction retourne une valeur quoi qu'il arrive. Mais le problème c'est qu'elle retourne des valeurs fausses sur 1 cas :

Code:

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main: call menuNext on label 'Exit'
main: label is now 'Back'

Le programme nous dit que le suivant de 'Exit' c'est 'Back'. C'est une erreur car 'Exit' n'a pas de suivant et 'Exit' devrait donc être retourné.

Donc ce n'est pas encore ça...
Comment parvenir à renvoyer 'Exit' lorsqu'on appel menuNext sur 'Exit' ?

Finalement au lieu de tricher sur les valeurs autant renvoyer NULL quand effectivement il n'y a plus d'élément suivant. Ça simplifie grandement le problème.
De toute façon, je pourrais toujours passer par une fonction intermédiaire qui vérifie si l'élément suivant est NULL. Dans ce cas, elle ne modifiera pas la position dans le menu.

Voici le code :

Code:

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#include<stdio.h> /* For printf, fprintf */
#include<stdlib.h> /* For NULL, stderr */
#include<string.h> /* For strcpy */
 
/* Structures */
typedef struct menu{
	char label[255];
	struct menu *next;
	struct menu *sub;
} Menu;
 
/* Functions */
Menu* menuCreate(char* label, Menu *next, Menu *sub){
	fprintf(stderr, "menuCreate: start\n");
	Menu *menu;
	menu = malloc(sizeof(Menu));
	strcpy(menu->label, label);
	menu->next = next;
	menu->sub = sub;
	fprintf(stderr, "\tmenuCreate: label='%s'\n", menu->label);
	fprintf(stderr, "menuCreate: end\n");
	return(menu);
}
 
Menu* menuNext(Menu *menu, char* label){
	fprintf(stderr, "menuNext: start\n");
	fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label);
 
	/* if it is found */
	if( (strcmp(menu->label, label) == 0) && (menu->next != NULL)){
		fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label);
		fprintf(stderr, "menuNext: end\n");
		return(menu->next);
	}
	else{
		/* if it has a sub */
		if(menu->sub != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label);
			return(menuNext(menu->sub, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a sub\n", menu->label);
		}
		/* if it has a next */
		if(menu->next != NULL){
			fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label);
			return(menuNext(menu->next, label));
		}
		else{
			fprintf(stderr, "\tmenuNext: label '%s' havn't a next\n", menu->label);
		}
	}
	fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label);
	return(NULL);
}

Les résultats sont satifsaisants pour mon ancien exemple.
Voici un nouvel exemple de menu :

http://gensiteweb.1s.fr/uploaded_fil..._next_sub2.png

Pour cet exemple, les résultats sont incorrects :

Code:

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$ ./a.out 2>/dev/null
 
main: call menuNext on label 'Play'
main: label is now 'Options'
 
main: call menuNext on label 'Options'
main: label is now '(null)'

En effet, l'élément suivant de 'Options' devrait être 'Exit'.

Voici le main :

Code:

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/* Main function */
int main(){
	Menu *menu1, *menu_current;
	menu1=menuCreate(
		"Play\0",
		menuCreate(
			"Options\0",
			menuCreate(
				"Exit\0",
				NULL,
				NULL
			),
			menuCreate(
				"Video\0",
				menuCreate(
					"Audio\0",
					menuCreate(
						"Control\0",
						menuCreate(
							"Game\0",
							menuCreate(
								"Back\0",
								NULL,
								NULL
							),
							NULL
						),
						NULL
					),
					NULL
				),
				NULL
			)
		),
		menuCreate(
			"1 player\0",
			menuCreate(
				"2 players\0",
				menuCreate(
					"Back\0",
					NULL,
					NULL
				),
				NULL
			),
			NULL
		)
	);
	menu_current=menu1;
 
	/* Call menuNext on 'Play' */
	printf("\nmain: call menuNext on label '%s'\n", "Play\0");
	menu_current=menuNext(menu1, "Play\0");
	printf("main: label is now '%s'\n", menu_current->label); /* Options */
	printf("\nmain: call menuNext on label '%s'\n", menu_current->label);
	menu_current=menuNext(menu1, menu_current->label);
	printf("main: label is now '%s'\n", menu_current->label); /* Exit */
return(0);
}

Je pense que le problème vient de l'instruction return dans menuNext, lorsqu'il y a un sub menu, qui provoque une interruption de la fonction. Dans ce cas, l'élément suivant (next) n'est pas parcouru...

Comment parvenir à parcourir complètement mon arbre même si des sub menus sont présents?

Trouvé!
Il fallait placer une conditionnelle sur un appel récursif :ccool:
Seulement si l'appel récursif est fructueux, alors effectuer un return.
Ca évite ainsi d'interrompre la fonction s'il on doit continuer :
Code:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Menu* menuNext(Menu *menu, char* label){ fprintf(stderr, "menuNext: start\n"); fprintf(stderr, "\tmenuNext: looking for next of label '%s'\n", label); Menu * menu_sub; /* if it is found */ if( (strcmp(menu->label, label) == 0) && (menu->next != NULL)){ fprintf(stderr, "\tmenuNext: next found (label='%s')\n", menu->next->label); fprintf(stderr, "menuNext: end\n"); return(menu->next); } /* if it has a sub */ if(menu->sub != NULL){ fprintf(stderr, "\tmenuNext: label '%s' have a sub\n", menu->label); if( (menu_sub = menuNext(menu->sub, label)) != NULL){ return(menu_sub); } } /* if it has a next */ if(menu->next != NULL){ fprintf(stderr, "\tmenuNext: label '%s' have a next\n", menu->label); return(menuNext(menu->next, label)); } fprintf(stderr, "\tmenuNext: no next found (label='%s')\n", menu->label); return(NULL); }
Les résultats sont corrects.
Seul problème, j'utilise comme clé de recherche de l'élément la chaine de caractères label. Or, il peut arriver que label ne soit pas unique dans l'ensemble du menu. Par exemple, 'Back' apparait deux fois dans l'ensemble du menu. Il faut donc que je travail directement sur l'adresse de menu, et non sur le label.

Voilà résolu donc :)