Function: while
Section: programming/control
C-Name: whilepari
Prototype: vEI
Help: while(a,seq): while a is nonzero evaluate the expression sequence seq.
 Otherwise 0.
Doc: while $a$ is nonzero, evaluates the expression sequence \var{seq}. The
 test is made \emph{before} evaluating the $seq$, hence in particular if $a$
 is initially equal to zero the \var{seq} will not be evaluated at all.
