 { $examples
     { $example
         "USING: math math.derivatives prettyprint ;"
-        "[ sq ] 4 derivative ."
+        "4 [ sq ] derivative >integer ."
         "8"
     }
     { $notes

        "when the error multiplies by 2. See " { $link check-safe } " for "
        "the enforcing code."
    }
}
{ $description
    "Approximates the slope of the tangent line by using Ridders' "

    }
} ;

HELP: derivative-func
{ $values { "func" "a differentiable function" } { "der" "the derivative" } }
{ $description
    "Provides the derivative of the function. The implementation simply "
