4 ms·

One other combination in Common Lisp is that lambda expressions are usable as the head of a form, in place of a function name: ;; Call a function object held

One other combination in Common Lisp is that lambda expressions are usable as the head of a form, in place of a function name: ;; Call a function object held in a variable (let ((add (lambda (a b) (+ a b)))) (funcall add 1 2)) vs ;; Direct execution of a lambda expression ((lambda (a b) (+ a b)) 1 2) Macro expansion can place a literal or generated lambda expression there instead of using FUNCALL at all.

sillysaurus3 9y ago
That's not actually a limitation of emacs lisp. It's just a design decision. I know exactly the spot in the code where they could do what you suggest, because I've often wondered why they don't. elisp gets a bad rap. But it's mostly self-inflicted. Also http://www.patrickkphillips.com/grammar/is-it-a-bad-rap-or-bad-rep/ http://www.patrickkphillips.com/grammar/is-it-a-bad-rap-or-b... A “rap sheet” is a criminal record, and a “bum rap” meant a false accusation (or even a false conviction). Even when the charge was valid, it should come as no surprise, a guilty party might claim it was a “bum rap” just to save face. Had no idea what a bad rap actually meant.
- microcolonel 9y ago
  It sure is lovely that a world has been created where most people don't even need to know what "rap sheet" means.
lisper 9y ago
> Macro expansion can place a literal or generated lambda expression there instead of using FUNCALL at all. Not quite. This, for example, does not work: (defmacro foo () '(lambda (x) x)) ((foo) 1) A macro can expand into a form whose CAR is a literal lambda expression, but because there is always an equivalent LET form I can't think of a circumstance where this can do anything but obfuscate the code. Personally, I think this is a flaw in the design of CL. Long ago I proposed an extension that would allow the CAR of a form to be a macro: http://www.flownet.com/ron/lisp/combination-hook.lisp http://www.flownet.com/ron/lisp/combination-hook.lisp I think it's cool for pedagogy because it lets you do things like directly define the Y combinator in CL without a ton of FUNCALLs. But it never caught on.

sillysaurus3 9y ago

That's not actually a limitation of emacs lisp. It's just a design decision. I know exactly the spot in the code where they could do what you suggest, because I've often wondered why they don't. elisp gets a bad rap. But it's mostly self-inflicted. Also http://www.patrickkphillips.com/grammar/is-it-a-bad-rap-or-bad-rep/ http://www.patrickkphillips.com/grammar/is-it-a-bad-rap-or-b... A “rap sheet” is a criminal record, and a “bum rap” meant a false accusation (or even a false conviction). Even when the charge was valid, it should come as no surprise, a guilty party might claim it was a “bum rap” just to save face. Had no idea what a bad rap actually meant.

microcolonel 9y ago
It sure is lovely that a world has been created where most people don't even need to know what "rap sheet" means.

lisper 9y ago

> Macro expansion can place a literal or generated lambda expression there instead of using FUNCALL at all. Not quite. This, for example, does not work: (defmacro foo () '(lambda (x) x)) ((foo) 1) A macro can expand into a form whose CAR is a literal lambda expression, but because there is always an equivalent LET form I can't think of a circumstance where this can do anything but obfuscate the code. Personally, I think this is a flaw in the design of CL. Long ago I proposed an extension that would allow the CAR of a form to be a macro: http://www.flownet.com/ron/lisp/combination-hook.lisp http://www.flownet.com/ron/lisp/combination-hook.lisp I think it's cool for pedagogy because it lets you do things like directly define the Y combinator in CL without a ton of FUNCALLs. But it never caught on.