3.7.2 Names in procedures

All variables are local to the procedure they are defined in. Locally defined variables cannot interfere with names in other procedures and are automatically deleted after leaving the procedure.

Internally, local variables are stored using the nesting level. A variable is said to have nesting level 1, if it is local to a procedure that was called interactively, nesting level 2, if it is local to a procedure that was called by a procedure of nesting level 1 etc. listvar() also displays the nesting level, nesting level 0 is used for global objects (see listvar). A ring may be ’moved up’ by one nesting level with keepring (see keepring). All variables living in that ring are moved together with that ring.

To keep local variables after leaving the procedure, they have to be exported (i.e. made known) to some higher level by the export command (see export).

Example:

proc xxx
{
  int k=4;        //defines a local variable k
  int result=k+2;
  export(result);  //defines the global variable "result".
}
xxx();
listvar(all);
→ // result               [0]  int 6
→ // LIB                  [0]  string standard.lib

Note that the variable result became a global variable after the execution of xxx.