diff options
| -rw-r--r-- | eval.c | 2 | ||||
| -rw-r--r-- | eval.h | 1 | ||||
| -rw-r--r-- | parser.y | 6 | ||||
| -rw-r--r-- | txr.1 | 124 |
4 files changed, 87 insertions, 46 deletions
@@ -5040,7 +5040,7 @@ static val gather_free_refs_nw(val info_cons, val exc, return uw_rthrow(continue_s, nil); } -static val expand_with_free_refs(val form, val menv_in, val upto_menv_in) +val expand_with_free_refs(val form, val menv_in, val upto_menv_in) { val ret; val menv = default_null_arg(menv_in); @@ -84,6 +84,7 @@ val expand_quasi(val quasi_forms, val menv); val load(val target); val expand(val form, val menv); val expand_forms(val forms, val menv); +val expand_with_free_refs(val form, val menv_in, val upto_menv_in); val prof_call(val (*fun)(mem_t *ctx), mem_t *ctx); val bindable(val obj); val mapcarv(val fun, struct args *lists); @@ -1519,7 +1519,11 @@ static val extract_vars(val output_spec) } } } - } else if (sym != expr_s) { + } else if (sym == expr_s) { + val expr = second(output_spec); + val frefs = expand_with_free_refs(expr, nil, nil); + tai = list_collect_nconc(tai, second(frefs)); + } else { for (; output_spec; output_spec = cdr(output_spec)) tai = list_collect_nconc(tai, extract_vars(car(output_spec))); } @@ -9156,79 +9156,115 @@ which counts from 1. The .code :vars -argument specifies a list of variable names, or pairs consisting of a variable -name and Lisp expression. For every variable paired with a Lisp expression, -the expression is evaluated, and a binding is introduced, associating -that variable with the expression's value. +argument specifies a list of variable name symbols +.meta symbol +or else pairs of the form +.mono +.meti >> ( symbol << init-form ) +.onom +consisting of a variable name and Lisp expression. Historically, the former +syntax informed +.code repeat +about references to variables contained in Lisp code. This usage is no +longer necessary as of \*(TX 243, since the +.code repeat +construct walks Lisp code, identifying all free variables. +The latter syntax introduces a new pattern variable binding for +.meta symbol +over the scope of the +.code repeat +construct. The +.meta init-form +specifies a Lisp expression which is evaluated to produce the +binding's value. The .code repeat directive then processes the list of variables, selecting from it -those which have a binding, either a previously existing binding or one just -introduced from a Lisp expression. For each selected variable, repeat -will assume that the variable occur in the repeat block and contains +those which have a binding, either a previously existing binding or the +one just introduced. For each selected variable, repeat +will assume that the variable occurs in the repeat block and contains a list to be iterated. -Thus +The variable binding syntax supported by .code :vars -Firstly, it is needed for situations in which \*(TL expressions which -reference variables are embedded in -.code @(repeat) -blocks. Variables references embedded in Lisp code are not found -.codn @(repeat) . -For instance, the following produces no output: +of the form +.mono +.meti >> ( symbol << init-form ) +.onom +provides a solution for situations when it is necessary to iterate +over some list, but that list is the result of an expression, and not stored in +any variable. A repeat block iterates only over lists emanating from variables; +it does not iterate over lists pulled from arbitrary expressions. + +Example: output all file names matching the +.code *.txr +pattern in the current directory: .verb - @(bind list ("a" "b" "c")) @(output) - @(repeat) - @(format nil "<~a>" list) + @(repeat :vars ((name (glob "*.txr")))) + @name @(end) @(end) .brev -Although the list variable appears in the repeat block, it is embedded -in a \*(TL construct. That construct will never be evaluated because -no repetitions take place: the repeat construct doesn't find any variables -and so doesn't iterate. The remedy is to provide a little help via -the :vars parameter: +Prior to \*(TX 243, the simple variable binding syntax supported by +.code :vars +of the form +.meta symbol +binding was needed for situations in which \*(TL expressions which +reference variables were embedded in +.code @(repeat) +blocks. Variables references embedded in Lisp code were not identified +.codn @(repeat) . +For instance, the following produced no output, because no variables +were found in the +.code repeat +body: .verb - @(bind list ("a" "b" "c")) + @(bind trigraph ("abc" "def" "ghi")) @(output) - @(repeat :vars (list)) - @(format nil "<~a>" list) + @(repeat) + @(reverse trigraph) @(end) @(end) .brev -Now the repeat block iterates over list and the output is: - -.verb - <a> - <b> - <c> -.brev - -Secondly, The variable binding syntax supported by +There is a reference to +.meta list +but it's inside a Lisp +.code "(reverse lisp)" +expression that was not processed by +.codn repeat . +The solution was to mention +.meta list +via the .code :vars -additionally provides a solution for situations when it is necessary to iterate -over some list, but that list is the result of an expression, and not stored in -any variable. A repeat block iterates only over lists emanating from variables; -it does not iterate over lists pulled from arbitrary expressions. - -Example: output all file names matching the -.code *.txr -pattern in the current directory: +construct: .verb + @(bind trigraph ("abc" "def" "ghi")) @(output) - @(repeat :vars ((name (glob "*.txr")))) - @name + @(repeat :vars (trigraph)) + @(reverse trigraph) @(end) @(end) .brev +Then the repeat block would iterates over list, producing the output: + +.verb + cba + fed + igh +.brev + +This workaround is no longer required as of \*(TX 243; the output +is produced by the first example, without +.codn :vars . + .coNP Nested @ repeat directives If a |