Discussion :

[YuGiOhJCJ]

Bonjour,

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

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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 :


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 :

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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.

[Lucien63]

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	if(menu->label==label){

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

[YuGiOhJCJ]

Ah oui bien vu

Voici la correction donc :

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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 :

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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'?

[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 ?

[YuGiOhJCJ]

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

Voici la correction :

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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 :

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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 :

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

Devrait être :

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menu = malloc(sizeof(Menu));

tout simplement.
Pas vrai?

[diogene]

Pas vrai?

Si évidemment !