Change: @(block) requires @(end) from now on.

Blocks no longer extend to the end of the surrounding
scope.

* match.c (v_block): Rewrite for new syntax.

* parser.l (BLOCK): New token type handled.

* parser.y (BLOCK): New token.
(block_clause): New nonterminal grammar symbol.
(clause): Collateral fix: replaced a bunch of
list(X, nao) forms with cons(X, nil).
Introduced block_clause as a constituent of clause.

* txr.1: Revamped documentation of block, and
wrote about using blocks for reducing nested
skips and reducing backtracking in general.

1 files changed, 6 insertions, 0 deletions

diff --git a/parser.l b/parser.l
index 98a243ec..f7a655db 100644
--- a/parser.l
+++ b/parser.l
@@ -257,6 +257,12 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
   return CASES;
 }
 
+<SPECIAL>\({WS}block/{ID_END} {
+  yy_push_state(NESTED);
+  yylval.lineno = lineno;
+  return BLOCK;
+}
+
 <SPECIAL>\({WS}choose/{ID_END} {
   yy_push_state(NESTED);
   yylval.lineno = lineno;