A look line takes `?re?` after its colon, as addr does

`file:?foo?`, `@p5:?foo?` and `:?foo?` were not taken for addresses (the
first character had to be one of `0-9+-/$.#,;`), so they went the path
way and found nothing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

3 files changed, 6 insertions, 3 deletions

diff --git a/docs/fs.md b/docs/fs.md
index fbf54c3e..2149fbcf 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -466,12 +466,12 @@ unfinished was cut short. A fragment never runs on its
 own. A line or Edit block held past 1 MiB is refused (EINVAL).
 
 `@p<serial>:<address>` addresses the pane with that serial as `file:<address>`
-does a file, with any sam address (`/re/`, `#n`, `$`, `0/re/`, a range),
+does a file, with any sam address (`/re/`, `?re?`, `#n`, `$`, `0/re/`, a range),
 a terminal too: its body is then the text of its logical lines (the lines
 a `+Search` of it lists), addressed from its cursor, and the match is
 selected. A miss, and a serial no pane has (with a line, `@p77:3`, as
 with any other address), each log an `err`, and look reads back empty. A look takes acme's addresses after a colon (editors/acme/look.c:450): a
-line written to `look` as `file:/re/`, `file:#n`, `file:$` or any address
+line written to `look` as `file:/re/`, `file:?re?`, `file:#n`, `file:$` or any address
 opens (or finds) the file and selects what the address names. **The
 address is evaluated from the file's dot**, as acme's is: `file:/re/`
 finds the next match after the current selection, not the first in the
diff --git a/src/look.zig b/src/look.zig
index cfebd42d..92e711fa 100644
--- a/src/look.zig
+++ b/src/look.zig
@@ -1266,7 +1266,7 @@ fn addressed(tok: []const u8) ?struct { path: []const u8, expr: []const u8 } {
     // pattern in the address may (`calc.py:/return a/`).
     if (std.mem.indexOfAny(u8, tok[0..colon], " \t") != null) return null;
     if (std.mem.indexOfAny(u8, expr, " \t") != null and std.mem.indexOfAny(u8, expr, "/?") == null) return null;
-    if (expr.len == 0 or std.mem.indexOfScalar(u8, "0123456789+-/$.#,;", expr[0]) == null) return null;
+    if (expr.len == 0 or std.mem.indexOfScalar(u8, "0123456789+-/?$.#,;", expr[0]) == null) return null;
     if (std.ascii.isDigit(expr[0])) {
         const pl = parsePathLine(tok);
         if (pl.at.line != 0 and pl.end == tok.len) return null;
diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index acb1b934..02201de0 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -1951,6 +1951,9 @@ test "@p<serial>:<address> takes any sam address; a miss and an unknown serial a
         .{ .addr = "#12,#15", .want = "         12          15 " },
         .{ .addr = "$", .want = "         16          16 " },
         .{ .addr = "1,2", .want = "          0          16 " },
+        // Backward, as in addr: from the dot's start, wrapping to the last.
+        .{ .addr = "?foo?", .want = "          6           9 " },
+        .{ .addr = "$-?y?", .want = "         10          11 " },
     }) |c| {
         var line: [64]u8 = undefined;
         try testing.expectEqual(Status.ok, wr(p, root, try std.fmt.bufPrint(&line, "@p{d}:{s}\n", .{ serial, c.addr })).reply.status);