diff options
| -rw-r--r-- | share/txr/stdlib/place.tl | 2 | ||||
| -rw-r--r-- | txr.1 | 12 |
2 files changed, 10 insertions, 4 deletions
diff --git a/share/txr/stdlib/place.tl b/share/txr/stdlib/place.tl index 6437ac45..dbae39be 100644 --- a/share/txr/stdlib/place.tl +++ b/share/txr/stdlib/place.tl @@ -139,7 +139,7 @@ (sys:setq place (sys:set-macro-ancestor [pm-expander unex-place] unex-place)))) - (sys:setq place (macroexpand place env)) + (sys:setq place (macroexpand-1 place env)) (when (or (eq place unex-place) (null place) (and (atom place) (not (symbolp place))) @@ -27430,15 +27430,21 @@ symbol in its leftmost position. Forms which are used as syntactic places are subject to a modified macro-expansion algorithm. If a place macro applies to a place, then it is expanded, otherwise it is taken as-is. Then the place is expanded as a ordinary -macro (possibly a symbol macro). Then the process is repeated from the -beginning, as necessary. Thus, the output of the ordinary macro expansion may -potentially be, again, a place macro. Place macros can expand to other place +macro (possibly a symbol macro), if possible, but only through at most +one round of macro-expansion, as if by +.codn macroexpand-1 . +If the macro-expansion succeeds, its its output might be, again, a place +macro form, and so the process is tried again. Place macros can expand to other place macros or ordinary macros and vice versa. Place macro expansion doesn't use an environment; place macros are in a single global namespace, special to place macros. There are no lexically scoped place macros. Such an effect can be achieved by having a place macro expand to an a form which is the target of a global or local macro, as necessary. +That said, it needs to be made clear that the ordinary macro-expansion +that may be interleaved within place-macro-expansion does take place +in the surrounding macro environment. A place macro can expand to a form +which matches a lexical macro visible at that point. The .code define-place-macro |