\DOC combine

\TYPE {combine : 'a list * 'b list -> ('a * 'b) list}

\SYNOPSIS
Transforms a pair of lists into a list of pairs.

\KEYWORDS
list.

\DESCRIBE
{combine ([x1,...,xn],[y1,...,yn])} returns {[(x1,y1),...,(xn,yn)]}.

\FAILURE
Fails if the two lists are of different lengths.

\COMMENTS
Has much the same effect as the SML Basis function {ListPair.zip}
except that it fails if the arguments are not of equal length. Also
note that {zip} is a curried version of {combine}

\SEEALSO
Lib.zip, Lib.unzip, Lib.split.
\ENDDOC