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.134The eval/1
function was first introduced by ECLiPSe and is under consideration for
YAP.