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!
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