An structure is a C-structure of this kind :
typedef struct _STRUC { char *nom_struc; int occup; struc_typ *type; char **nom_mb; } strucb;
nom_struc is the name of the structure.
occup is 0 if the structure has not been initialized, 1 otherwise.
type is the address of the structure type of the structure (cf. 6.8).
nom_mb[i] is the name of the object (or structure) which is the member i of the structure (if this member is not a variable of the expression evaluator). It will be NULL if this member has not been assigned.