Équivalence

.gitignore

@@ -2,5 +2,7 @@ exclude-executables.sh
 lexical/example
 lexical/flux
 lexical/string
+syntaxique/expr
+syntaxique/lang
 *.c
 *.o

syntaxique/lang.y

@@ -30,7 +30,7 @@ typedef struct varlist	// variable reference (used for print statement)
 
 typedef struct expr	// boolean expression
 {
-	int type;	// TRUE, FALSE, OR, AND, NOT, 0 (variable)
+	int type;	// TRUE, FALSE, OR, AND, EQUIV, NOT, 0 (variable)
 	var *var;
 	struct expr *left, *right;
 } expr;
@@ -130,6 +130,7 @@ stmt* make_stmt (int type, var *var, expr *expr,
 %left OR XOR
 %left AND
 %right NOT
+%left EQUIV
 
 %%
 
@@ -158,6 +159,7 @@ expr	: IDENT		{ $$ = make_expr(0,find_ident($1),NULL,NULL); }
 	| expr XOR expr	{ $$ = make_expr(XOR,NULL,$1,$3); }
 	| expr OR expr	{ $$ = make_expr(OR,NULL,$1,$3); }
 	| expr AND expr	{ $$ = make_expr(AND,NULL,$1,$3); }
+	| expr EQUIV expr 	{ $$ = make_expr(EQUIV,NULL,$1,$3); }
 	| NOT expr	{ $$ = make_expr(NOT,NULL,$2,NULL); }
 	| TRUE		{ $$ = make_expr(TRUE,NULL,NULL,NULL); }
 	| FALSE		{ $$ = make_expr(FALSE,NULL,NULL,NULL); }
@@ -179,6 +181,12 @@ int eval (expr *e)
 		case XOR: return eval(e->left) ^ eval(e->right);
 		case OR: return eval(e->left) || eval(e->right);
 		case AND: return eval(e->left) && eval(e->right);
+		case EQUIV: {
+			int right = eval(e->right);
+			int left = eval(e->left);
+			return (right && left) || (!right && !left);  // Équivalent avec left == right avec la définition.
+														  // Toutefois, on privilégie cette forme car faux = 0 et vrai = tout entier non nul.
+		}
 		case NOT: return !eval(e->left);
 		case 0: return e->var->value;
 	}

syntaxique/langlex.l

@@ -17,6 +17,7 @@ DIG	[0-9]
 "||"	{ return OR; }
 "&&"	{ return AND; }
 "!"		{ return NOT; }
+"<=>"	{ return EQUIV; }
 
 [a-z_][a-z0-9_]* { yylval.i = strdup(yytext); return IDENT; }
 

syntaxique/test.my

@@ -0,0 +1,21 @@
+bool x,y,z;
+
+x := true;
+y := true;
+z := x <=> y;
+print x,y,z;
+
+x := true;
+y := false;
+z := x <=> y;
+print x,y,z;
+
+x := false;
+y := true;
+z := x <=> y;
+print x,y,z;
+
+x := false;
+y := false;
+z := x <=> y;
+print x,y,z