If you do not specify the package for the iteration, the current package is used. If you specify a package that does not exist, an error is signaled. The package to be iterated over is specified in the same way that package arguments to the Common Lisp function find-package are specified. If you do not specify the package for the iteration, the current package is used. If you specify a package that does not exist, an error is signaled.
Iteration stops when there are no more symbols to be referenced in the specified package.
The loop body is executed n times, where n is the value of the expression expr . The expr argument is evaluated one time in the loop prologue. If the expression evaluates to zero or to a negative number, the loop body is not evaluated.