diff options
| -rw-r--r-- | ChangeLog | 9 | ||||
| -rw-r--r-- | RELNOTES | 5 | ||||
| -rw-r--r-- | parser.y | 38 | ||||
| -rw-r--r-- | txr.1 | 46 |
4 files changed, 51 insertions, 47 deletions
@@ -1,5 +1,14 @@ 2011-12-04 Kaz Kylheku <kaz@kylheku.com> + * parser.y (force_regular_quotes): Function removed. + (list): Prior commit reversed. + + * txr.1: Prior commit reversed. + + * RELNOTES: No semantics clarification in quasiquote; bugfixes only. + +2011-12-04 Kaz Kylheku <kaz@kylheku.com> + * eval.c (op_qquote_error, op_unquote_error): New static functions. (expand_qquote): Bugfix: missing case added to handle directly quoted quasiquote. @@ -6,12 +6,13 @@ - New functions exposed in Lisp interpreter: strings, characters, symbols and lazy lists. - - Quasiquote semantics clarified. - Bugs - Flaws in some string-splitting functions identified and fixed. + - Bugs in quasiquote. + + TXR 044 @@ -50,7 +50,6 @@ static val define_transform(val define_form); static val lit_char_helper(val litchars); static val optimize_text(val text_form); static val choose_quote(val quoted_form); -static val force_regular_quotes(val form); static wchar_t char_from_name(wchar_t *name); static val parsed_spec; @@ -608,14 +607,16 @@ var_op : '*' { $$ = list(t, nao); } list : '(' exprs ')' { $$ = rl($2, num($1)); } | '(' ')' { $$ = nil; } - | ',' expr { $$ = rlcp(list(unquote_s, - force_regular_quotes($2), nao), - $2); } + | ',' expr { val expr = $2; + if (consp(expr) && first(expr) == qquote_s) + expr = cons(quote_s, rest(expr)); + $$ = rlcp(list(unquote_s, expr, nao), $2); } | '\'' expr { $$ = rlcp(list(choose_quote($2), $2, nao), $2); } - | SPLICE expr { $$ = rlcp(list(splice_s, - force_regular_quotes($2), nao), - $2); } + | SPLICE expr { val expr = $2; + if (consp(expr) && first(expr) == qquote_s) + expr = cons(quote_s, rest(expr)); + $$ = rlcp(list(splice_s, expr, nao), $2); } | '(' error { $$ = nil; yybadtoken(yychar, lit("list expression")); } ; @@ -911,29 +912,6 @@ static val choose_quote(val quoted_form) return unquotes_occur(quoted_form) ? qquote_s : quote_s; } -static val force_regular_quotes(val form) -{ - if (atom(form)) { - return form; - } else { - val sym = car(form); - val body = cdr(form); - - if (sym == qquote_s) { - return rlcp(cons(quote_s, force_regular_quotes(body)), form); - } if (sym == unquote_s || sym == splice_s) { - return form; - } else { - val car_sub = force_regular_quotes(sym); - val cdr_sub = force_regular_quotes(body); - - if (car_sub == sym && cdr_sub == body) - return form; - return rlcp(cons(car_sub, cdr_sub), form); - } - } -} - val rl(val form, val lineno) { sethash(form_to_ln_hash, form, lineno); @@ -4223,16 +4223,11 @@ value of 'a is the symbol a itself, whereas the value of a is the value of the variable a. Note that TXR Lisp does not have a distinct quote and backquote syntax. -There is only one quote, which supports unquoting. The quote behaves -either like a quasiquote or a regular quote according to these rules: +There is only one quote, which supports unquoting. -1. A quoted form which contains no unquotes or splices is an ordinary quote. +A quoted form which contains no unquotes codifies an ordinary quote. -2. Quotes occuring within forms that are unquoted or spliced are ordinary -quotes, not quasiquotes. - -3. Quotes which contain unquotes and splices and are not within unquotes -or splices are quasiquotes. +A quoted form which contains unquotes expresses a quasiquote. .IP ,form @@ -4244,13 +4239,34 @@ in the quote stands for itself, except for the ,(+ 2 2) which is evaluated. .IP ,*form -The comma-star operator is used within a quoted list to denote a splicing -unquote. Wheras the quote suppresses evaluation, the comma introduces an -exception: the form which follows ,* must evaluate to a list. That list is -spliced into the quoted list. For example: '(a b c ,*(list (+ 3 3) (+ 4 4) d) -evaluates to (a b c 6 8 d). The expression (list (+ 3 3) (+ 4 4)) is evaluated +The comma-star operator is used within a quoted list to denote a splicing unquote. +Wheras the quote suppresses evaluation, the comma introduces an exception: +the form which follows ,* must evaluate to a list. That list is spliced into +the quoted list. For example: '(a b c ,*(list (+ 3 3) (+ 4 4) d) evaluates +to (a b c 6 8 d). The expression (list (+ 3 3) (+ 4 4)) is evaluated to produce the list (6 8), and this list is spliced into the quoted template. +.IP ,'form + +The comma-quote combination has a special meaning: the quote always +behaves as a regular quote and not a quasiquote, even if form contains +unquotes. Therefore, it does not "capture" these unquotes: they cannot +"belong" to this quote. The comma and quote "cancel out", so the only effect +of comma-quote is to add one level of unquoting. So for instance, whereas in +'(a b c '(,d)), the subsitution of d belongs to the inner quote (it is unquoted +by the leftmost comma which belongs to the innermost quote) by contrast, +in '(a b c '(,',d)) the d is now one comma removed from the leftmost comma and +thus the substitution of d belongs to the outer quote. +In other dialects of Lisp, this would be written `(a b c `(,',d)), making it +explicit which kind of quote is being specified. TXR Lisp works out which +kind of quote to use internally. + +.IP ,*'form + +The comma-splice form is analogous to comma-quote (see above). Like in the +,' combination, in the ,*' combination, the quote behaves as a regular quote +and not a quasiquote. + .PP .SS Nested Quotes @@ -4263,8 +4279,8 @@ quote, which protects it from evaluation. To get the (+ 1 2) value "through" to the inner quote, the unquote syntax must also be nested using multiple commas, like this: '(1 2 3 '(4 5 6 ,',(+ 1 2))). The leftmost comma goes with the innermost quote. The quote between the commas protects the (+ 1 2) -from repeated evaluations. According to rule 2 above, it is a regular -quote, and so it does not capture the following comma. +from repeated evaluations: the two unquotes call for two evaluations, but +we only want (+ 1 2) to be evaluated once. .SS Lisp Operators |