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I may be imposing my own views on his wording, but my interpretation is that his concern is related to the fact that macros have similar syntax to everything el

I may be imposing my own views on his wording, but my interpretation is that his concern is related to the fact that macros have similar syntax to everything else in the language. Consider these two forms: > (and a b c) > (and* a b c) Can you tell by looking that the the first is a macro and the second is a function? The first short circuits and evaluates only the argument forms it needs and the second always evaluates all three. That's a big difference, and not at all obvious from the syntax. In fact, it's hidden by the syntax, because the syntax is exactly the same for each. Macros are part of the power of Lisp, but they change the normal rules of evaluation (the semantics) in ways that are not necessarily obvious unless you know the specific definitions behind each symbol in function position.

andrekandre 5y ago
thanks, i think that makes it more clear for ^^
kazinator 5y ago
We can usefully be both a macro/operator and function under the same symbol: This is the TXR Lisp interactive listener of TXR 268. Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet. 1> (special-operator-p 'and) t 2> (fboundp 'and) t 3> (fun and) #<intrinsic fun: 0 param + variadic> 4> (and 23 nil (prinl 42)) nil 5> (call 'and 23 nil (prinl 42)) 42 nil 6> [and 23 nil (prinl 42)] 42 nil 7> [mapcar if '(nil t t nil) '(1 2 3 4) '(a b c d)] (a 2 3 d) 8> (if t (prinl 'true) (prinl 'false)) true true 9> [if t (prinl 'true) (prinl 'false)] true false true If we use the functional brackets, all arguments are evaluated the same way, and the leftmost value is treated as a callable object applied to the remaining values. A symbol in the leftmost position of [...] is never treated as a macro (other than symbol macro) or special operator, even if it has a such a binding.

andrekandre 5y ago

thanks, i think that makes it more clear for ^^

kazinator 5y ago

We can usefully be both a macro/operator and function under the same symbol: This is the TXR Lisp interactive listener of TXR 268. Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet. 1> (special-operator-p 'and) t 2> (fboundp 'and) t 3> (fun and) #<intrinsic fun: 0 param + variadic> 4> (and 23 nil (prinl 42)) nil 5> (call 'and 23 nil (prinl 42)) 42 nil 6> [and 23 nil (prinl 42)] 42 nil 7> [mapcar if '(nil t t nil) '(1 2 3 4) '(a b c d)] (a 2 3 d) 8> (if t (prinl 'true) (prinl 'false)) true true 9> [if t (prinl 'true) (prinl 'false)] true false true If we use the functional brackets, all arguments are evaluated the same way, and the leftmost value is treated as a callable object applied to the remaining values. A symbol in the leftmost position of [...] is never treated as a macro (other than symbol macro) or special operator, even if it has a such a binding.