Re: proper use of define-alias

[Chuah Teong Leong <teongleong at gmail dot com>]

A shorter version of my question is as follows

(define-alias vert-sb-always
<javax.swing.ScrollPaneConstants>:VERTICAL_SCROLLBAR_ALWAYS)

(define-alias hori-sb-always
<javax.swing.ScrollPaneConstants>:HORIZONTAL_SCROLLBAR_ALWAYS)

;; this doesnt work
(let ((myvar vert-sb-always)
       (myvar2 hori-sb-always))

(make-scrollpane-with-policy in-component
 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? myvar myvar2))

why cant i assign a temp variable like that and use it like that?


in the previous example using vpolicy and hpolicy throws an exception

;; choose the correct constant based on the symbol passed in
 (define vpolicy
   (case vp-sym
     ((always) vert-sb-always)
     ((needed) vert-sb-needed)
     ((never) vert-sb-never)
     (else (display "Error unknown policy ")(display vp-sym)
           vert-sb-needed)))

  (define hpolicy
   (case hp-sym
     ((always) hori-sb-always)
     ((needed) hori-sb-needed)
     ((never) hori-sb-never)
     (else (display "Error unknown policy ")(display hp-sym)
           hori-sb-needed)))

  (<javax.swing.JScrollPane> in-component vpolicy hpolicy)

whereas...

this works
 (<javax.swing.JScrollPane>
   in-component
   (case vp-sym
     ((always) vert-sb-always)
     ((needed) vert-sb-needed)
     ((never) vert-sb-never)
     (else (display "Error unknown policy ")(display vp-sym)
           vert-sb-needed))
     (case hp-sym
     ((always) hori-sb-always)
     ((needed) hori-sb-needed)
     ((never) hori-sb-never)
     (else (display "Error unknown policy ")(display hp-sym)
           hori-sb-needed)))

so essentially my problem is with why there's a problem with assigning
a temp variable to the define-alias variables


On Thu, Jun 21, 2012 at 11:11 PM, Chuah Teong Leong
<teongleong@gmail.com> wrote:
> hi. I'm new to the use of define-alias and I was trying to use it as follows.
>
> Exception:
> Value '20' for variable 'vpolicy' has wrong type (java.lang.Integer) (java.lang.
> Integer cannot be cast to gnu.mapping.Location)
>
> (define-alias vert-sb-always
> <javax.swing.ScrollPaneConstants>:VERTICAL_SCROLLBAR_ALWAYS)
> (define-alias vert-sb-needed
> <javax.swing.ScrollPaneConstants>:VERTICAL_SCROLLBAR_AS_NEEDED)
> (define-alias vert-sb-never
> <javax.swing.ScrollPaneConstants>:VERTICAL_SCROLLBAR_NEVER)
>
> (define-alias hori-sb-always
> <javax.swing.ScrollPaneConstants>:HORIZONTAL_SCROLLBAR_ALWAYS)
> (define-alias hori-sb-needed
> <javax.swing.ScrollPaneConstants>:HORIZONTAL_SCROLLBAR_AS_NEEDED)
> (define-alias hori-sb-never
> <javax.swing.ScrollPaneConstants>:HORIZONTAL_SCROLLBAR_NEVER)
>
> (define (make-scrollpane in-component :: <javax.swing.JComponent>)
> ?(<javax.swing.JScrollPane> in-component))
>
> ;; make a scrollpane with policy
> (define (make-scrollpane-with-policy in-component :: <javax.swing.JComponent>
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? vp-sym :: <symbol>
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? hp-sym :: <symbol> )
>
> ;; choose the correct constant based on the symbol passed in
> ?(define vpolicy
> ? ?(case vp-sym
> ? ? ?((always) vert-sb-always)
> ? ? ?((needed) vert-sb-needed)
> ? ? ?((never) vert-sb-never)
> ? ? ?(else (display "Error unknown policy ")(display vp-sym)
> ? ? ? ? ? ?vert-sb-needed)))
>
> ? (define hpolicy
> ? ?(case hp-sym
> ? ? ?((always) hori-sb-always)
> ? ? ?((needed) hori-sb-needed)
> ? ? ?((never) hori-sb-never)
> ? ? ?(else (display "Error unknown policy ")(display hp-sym)
> ? ? ? ? ? ?hori-sb-needed)))
>
> ? (<javax.swing.JScrollPane> in-component vpolicy hpolicy)
> ?)
>
> What is the proper way of doing what I want to do here?