[Richard Suchenwirth] 2002-11-14 - A ''reference'' is something that refers, or points, to another something (if you pardon the scientific expression). In C, references are done with *pointers* (memory addresses); in Tcl, references are strings ([everything is a string]), namely names of variables, which via a hash table can be resolved (dereferenced) to the "other something" they point to:
 puts foo       ;# just the string foo
 puts $foo      ;# dereference variable with name of foo
 puts [set foo] ;# the same
This can be done more than one time with nested [set] commands. Compare the following C and Tcl programs, that do the same (trivial) job, and exhibit remarkable similarity:
 #include <stdio.h>
 int main(void) {
   int    i =      42;
   int *  ip =     &i;
   int ** ipp =   &ip;
   int ***ippp = &ipp;
   printf("hello, %d\n", ***ippp);
   return 0;
 }
...and Tcl:
 set i    42
 set ip   i
 set ipp  ip
 set ippp ipp
 puts "hello, [set [set [set ipp]]]"
The C asterisks correlate to [set] calls in derefencing, while in Tcl similar markup is not needed in declaring.

(This little piece was written to defuse the superstition that Tcl has no references, or needs more of the same. See also [Pass by reference].
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