Function: foreach
Section: programming/control
C-Name: foreachpari
Prototype: vGVI
Help: foreach(V,X,seq): the sequence is evaluated, X running over the
 components of V.
Doc: evaluates \var{seq}, where the formal variable $X$ ranges through the
 components of $V$ (\typ{VEC}, \typ{COL}, \typ{LIST} or \typ{MAT}). A matrix
 argument is interpreted as a vector containing column vectors, as in
 \kbd{Vec}$(V)$.
