DROP

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 ────DROP───┴───name────┴────;─────────────────

Each name is a valid variable symbol, optionally enclosed in parentheses (to denote a subsidiary list), and separated from any other name by one or more blanks or comments.

DROP is used to unassign variables; that is, to restore them to their original uninitialized state.

Each variable specified is dropped from the list of known variables. If a single name is enclosed in parentheses, then its value is used as a subsidiary list of variables to drop. This stored list must follow the same rules as for the main list (that is, valid variable names, separated by blanks) but with no parentheses and no leading or trailing blanks. The variables are dropped in sequence from left to right. It is not an error to specify a name more than once, or to DROP a variable that is not known. If an exposed variable is named (see the PROCEDURE instruction), the variable itself in the older generation is dropped.

Example:

j=4
Drop  a x.3 x.j
/* would reset the variables: A, X.3, and X.4 */
/* so that reference to them returns their name.    */

Here, a variable name in parentheses is used as a subsidiary list.

Example:

x=4;y=5;z=6;
a='x y z'
DROP (a)    /* will drop x,y, and z */

If a stem is specified (that is, a symbol that contains only one period, as the last character), all variables starting with that stem are dropped.

Example:

Drop  x.
/* would reset all variables with names starting with X. */