1typedef struct entry entry;23struct entry {4 char *key;5 int value;6 entry *next;7};89typedef struct env env;1011struct env {12 int size;13 entry **entries;14};1516env *newenv(int s);17void freeenv(env *e);18int setval (env *e, char *k, int v);19int getval (env *e, char *k, int *d);20int updval (env *e, char *k, int v);