June 2018 Update

Task/Runtime-evaluation-In-an-environment/Julia/runtime-evaluation-in-an-environment-1.julia

@@ -0,0 +1,10 @@
+macro evalwithx(expr, a, b)
+    return quote
+        x = $a
+        tmp = $expr
+        x = $b
+        return $expr - tmp
+    end
+end
+
+@evalwithx(2 ^ x, 3, 5)     # raw expression (AST)

Task/Runtime-evaluation-In-an-environment/Julia/runtime-evaluation-in-an-environment-2.julia

@@ -0,0 +1,9 @@
+function evalwithx(expr::Expr, a, b)
+    a = eval(quote let x = $a; return $expr end end)
+    b = eval(quote let x = $b; return $expr end end)
+    return b - a
+end
+evalwithx(expr::AbstractString, a, b) = evalwithx(parse(expr), a, b)
+
+evalwithx(:(2 ^ x), 3, 5)
+evalwithx("2 ^ x", 3, 5)