visual c++ - How can I write a method to determine the typedef type at runtime? -

i have binary search tree want implement different types. binary search tree templated , determined using following statement:

typedef desiredtype treeitemtype; // desired type of tree items i.e. string, int, person 

normally change desiredtype string tree of strings if want make tree of integers? i'm thinking need make method determining typdef type @ runtime don't know begin because desiredtype can variety of variable object types. ideas?

it hard tell 1 line, looks use c preprocessor command

#define savedesiredtype desiredtype    // save previous setting #define desiredtype char*                 // change type     ... <code>  #define  desiredtype savedesiredtype  // restore previous setting 

however, think may define particular typedef once in module (object file .o).

the way know create workable tree structures of variable types in c go pointer manipulation model, or add type parameter tree functions, , pointer math different sizes of types.
more object centric approach woul encapsulate data in tree_node struct type data.

typedef enum d_type { anint , afloat, adouble, achar, astring, other} datatype;     typedef struct t_node{ datatype dtype; union {   // union 1 of following types, , one.        int i;    // size of union size of largest type.         float f;        double d;        char c;        char* string;       }   // union unnamed , have name. } tree_node;  typedef tree_node* treeitem;  //pass reference 

in code must switch on node->dtype , work variable of type.

void tree_add (tree t, treeitem item) {   int i;   float f;   double d;   char c;   char* s;    switch (item->dtype){     case anint:       = item->i;       break;     case afloat:       f = item->f;       break;     case adfloat:       d = item->d;       break;     ...    }//switch     ...<code> }//tree_add  double pi = 3.141592653589793238; treeitem ti = ( treeitem ) malloc (sizeof(tree_node) ); // struct must allocated ti->dtype = adouble; ti->d = pi;  ti->s = pi; /* oops! error. (might go through without being detected -- depending on compiler) */  tree_add( atree , ti);  ti->s = "now time programmers come aid of computers.";   /* oops! error. undefined behavior double d?   (this might go through without being detected -- depending on compiler )    ti->dtype not changed either code break. */ 

(seems work, doesn't it?)