Your explanation of "lambda _" jogged my memory. I'm remembering long ago Haskell learnings where the underscore is used in much the same way.
I'll take a look at the two references you shared. This is a really useful starting point. Thank you again, Laurent. On Tue, Nov 2, 2021 at 5:35 AM Laurent <[email protected]> wrote: > On Mon, Nov 1, 2021 at 11:14 PM James Zollinger <[email protected]> wrote: > >> Thanks for the info, Laurent. I tried the trick outlined in the link you >> sent me on Debian 11 versions of Gnome 3.38.5 (just to test this) and MATE >> 1.24.1-2 (my preferred environment) without any success. >> > > I haven't tried myself. For what it's worth, I wrote another quickscript > called "command palette" that does exactly that, but of course specifically > for DrRacket (*): > https://gist.github.com/Metaxal/d06f50a2534ca229309e71a2d244a912 > > Again it doesn't look into context (right click) menus as they are not > easily accessible. > > (*) Actually, it could be used with any Racket GUI app! > > >> My LISP/scheme/racket skills are maturing but I'm not quite ready to >> tackle: >> (when (cons? stat) >> (make-object menu-item% >> "Print return value to console" menu >> (lambda _ (send (get-tab) print-to-console >> (string-append "return val = " >> rendered-value))))) >> and friends! (What is "lambda _"?!) >> > > Yeah, that can seem weird, but it will make sense. Let me explain in > examples: > > (define f (lambda (x) (displayln x))) > (f 3) ; ok > (f 3 4 5) ; not ok > (f) ; not ok > > (define g (lambda (x . rst) (displayln (list x rst)))) > (g 3) ; ok, equiv to (displayln '(3 ()), rst is the empty list > (g 3 4 5) ; ok, equiv to (displayln '(3 (4 5))) > (g) ; not ok, needs at least 1 argument > > (define h (lambda lst (displayln lst))) > (h 3) ; equiv to (displayln '(3)) > (h 3 4 5) ; equiv to (displayln '(3 4 5)) > (h) ; equiv to (displayln '()) > > Now, `_` is just an identifier like any other, like `lst`, but by (untold) > convention it means "I won't use this argument". So > (define k (lambda _ (displayln "hoy"))) > (k) ; equiv to (displayln "hoy") > (k 3 4 5) ; equiv to (displayln "hoy") > > >> Any suggestions on how to quickly get up to speed to >> modify debug-tool.rkt beyond reading all of the Racket Documentation >> <https://docs.racket-lang.org/>? >> > > debug-tool.rkt is probably not the best first encounter with Racket. It > draws on many concepts (macros, classes, gui, etc.). Though if you do > manage to make sense of it you may learn a lot :) > > For this particular task, even though the file contains "units", I think > you shouldn't have to understand units, but you will certainly have to > understand Racket classes: > https://docs.racket-lang.org/guide/classes.html > and part of the GUI: > https://docs.racket-lang.org/gui/index.html > > HTH, > Laurent > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAN-sgtKa_3HNU1UNQnyhU3Hu3K7Lz%3D_WvFY-n5fbyf2eLFhvjw%40mail.gmail.com.
