Availability:Arithmetic function (see is/2)
eval(+Expr)Evaluate Expr. Although ISO standard dictates that `A=1+2, B
is
A' works and unifies B to 3, it is widely felt
that source level variables in arithmetic expressions should have been
limited to numbers. In this view the eval function can be used to
evaluate arbitrary expressions.118The eval/1
function was first introduced by ECLiPSe and is under consideration for
YAP.