unzip : ('a * 'b) list -> ('a list * 'b list)
STRUCTURE
SYNOPSIS
Converts a list of pairs into a pair of lists.
DESCRIPTION
unzip [(x1,y1),...,(xn,yn)] returns ([x1,...,xn],[y1,...,yn]).
FAILURE
Never fails.
COMMENTS
Identical to Lib.split.
SEEALSO
HOL  Kananaskis-13