(phixonline)-->
without javascript_semantics
requires("1.0.1")
include eval.e
function eval_with_x(string expr, integer a, b)
return eval(expr,{"x"},{{"x",b}})[1] -
eval(expr,{"x"},{{"x",a}})[1]
end function
?eval_with_x("integer x = power(2,x)",3,5)