I don't get it , can you explain in terms of environment and interpretation .
The simplistic view that I have is : The body of a function executes , it encounters define form so expression part of define is evaluated and bound to identifier part of define in a environment , it then encounters the identifier color and then value of color is returned. Sorry if I am using wrong terminology. Thanks. On Sun, Jul 10, 2011 at 11:28 AM, Eli Barzilay <e...@barzilay.org> wrote: > 10 minutes ago, Veer wrote: >> Following code returns #<undefined> : >> >> (define (make-color color) >> (define color color) >> color) >> >> (make-color 'red) ;; => #<undefined> >> >> From the guide , I get that internal definition of color is not initialized >> therefore the result is #<undefined> . What does not initialized means >> in this context. > > You're defining a new `color', one that shadows the `color' input. If > you click check-syntax and hover over the different `color's you'll > see helpful arrows that indicate the bindings. (For the argument > you'll see *no* errors.) `define' is basically defining a new > identifier -- it's different from `set!', and sometimes confused since > in many languages `=' is used for both. > > >> My assumption was that internal color will be bound to the value of >> argument. >> >> When was #<undefined> introduced (or it was always there). > > It was always there. (Or at least since the time I started using > MzScheme, which was around 1854.) > > >> I "think" I have used this type of code before , and it worked fine >> then. > > No, it always did that... > > -- > ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: > http://barzilay.org/ Maze is Life! > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
