Function: until
Section: programming/control
C-Name: untilpari
Prototype: vEI
Help: until(a,seq): evaluate the expression sequence seq until a is nonzero.
Doc: evaluates \var{seq} until $a$ is not
 equal to 0 (i.e.~until $a$ is true). If $a$ is initially not equal to 0,
 \var{seq} is evaluated once (more generally, the condition on $a$ is tested
 \emph{after} execution of the \var{seq}, not before as in \kbd{while}).
