@(next) takes Lisp expression as source now.

* match.c (v_next): Evaluate the source expression as TXR Lisp,
unless it is meta-expression or meta-variable, or
the compatibility option is set to 124 or lower.
In those cases treat it as an expression of the TXR Pattern

* txr.1: Updated documentation of @(next) and all
relevant examples of @(next) everywhere.
Added compatibility notes.

2 files changed, 36 insertions, 3 deletions

diff --git a/match.c b/match.c
index 71ea60c2..004306fc 100644
--- a/match.c
+++ b/match.c
@@ -2398,6 +2398,7 @@ static val v_next(match_files_ctx *c)
   if (rest(first_spec)) {
     val args = rest(first_spec);
     val source = first(args);
+    val meta = nil;
 
     if (source == args_k) {
       if (rest(args)) {
@@ -2427,6 +2428,15 @@ static val v_next(match_files_ctx *c)
       }
     }
 
+    if (consp(source)) {
+      val sym = car(source);
+      if (sym == var_s || sym == expr_s)
+        meta = t;
+    }
+
+    if (opt_compat && opt_compat <= 124)
+      meta = t;
+
     if (keywordp(first(args))) {
       source = nil;
     } else {
@@ -2442,7 +2452,10 @@ static val v_next(match_files_ctx *c)
       val list_expr = cdr(assoc(list_k, alist));
       val string_expr = cdr(assoc(string_k, alist));
       val nothrow = cdr(assoc(nothrow_k, alist));
-      val str = txeval(specline, source, c->bindings);
+      val str = if3(meta,
+                    txeval(specline, source, c->bindings),
+                    eval_with_bindings(source, specline, c->bindings,
+                                       specline));
 
       if (!from_var && !source && !string_expr && !list_expr)
         sem_error(specline, lit("next: source required before keyword arguments"), nao);
diff --git a/txr.1 b/txr.1
index 0c738ac6..4aba9eb3 100644
--- a/txr.1
+++ b/txr.1
@@ -3071,7 +3071,7 @@ to \*(TX on the command line.
 
 If
 .meta source
-is given, it must be string-valued expression which denotes an
+is given, it must be string-valued Lisp expression which denotes an
 input source; it may be a string literal, quasiliteral or a string-valued
 variable.  For instance, if variable
 .code A
@@ -32444,7 +32444,7 @@ Collect lines from all files that are given as arguments on the command line. If
 there are no files, then read from standard input:
 
 .cblk
-   @(next @(open-files *args* *stdin*))
+   @(next (open-files *args* *stdin*))
    @(collect)
    @line
    @(end)
@@ -37770,6 +37770,26 @@ of these version values, the described behaviors are provided if
 is given an argument which is equal or lower. For instance
 .code -C 103
 selects the behaviors described below for version 105, but not those for 102.
+.IP 124
+In \*(TX 124 and earlier versions, the
+.code @(next)
+directive didn't evaluate the
+.meta source
+argument as a Lisp expression, but as a \*(TX Pattern Language
+expression. Lisp expressions thus had to be delimited by
+.codn @ .
+The current behavior is that the argument is treated as Lisp.
+If the compatibility option is set to 124 or lower, the old behavior
+is restored. However, even without the presence of the compatibility option,
+if the
+.meta source
+argument is a meta-expression or meta-variable (denotes by the
+.code @
+prefix in front of a compound expression or symbol, respectively)
+it is also treated in the old way. This latter behavior is obsolescent
+and will eventually disappear, and the compatibility option will be
+the only way to get the old behavior.
+
 .IP 123
 In \*(TX 123 and earlier, the variable initialization forms of a
 .code for