addr takes line:col, as Look's file:12:5 does

A script that knows a line and column had to count bytes to write #n. `12:5` is now the point at line 12, column 5 (bytes from 1, clamped to the line's end and snapped to a character's start, as Look's cursor is), and it composes like any simple address. A pardes extension, documented as one; sam reads it as a syntax error.

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

1 files changed, 12 insertions, 2 deletions

diff --git a/docs/fs.md b/docs/fs.md
index f23129ba..d746ec28 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -357,10 +357,20 @@ exec 3>&-`.
 The three range files `addr`, `dot` and `limit` each read the pair of offsets
 they also accept, so copying one onto another is all that acme's `addr=dot`,
 `dot=addr` and `limit=addr` ever were. A write is either that pair or an
-address expression (`#0,#5`, `/pattern/`, `2+1`); `addr` selects what `data`
+address expression (`#0,#5`, `/pattern/`, `2+1`, and pardes's own `12:5`,
+below); `addr` selects what `data`
 and `xdata` read or replace, `dot` is the editor's own selection and moving it
 scrolls the pane into view, and `limit` bounds a search and reads empty until
-it is set. Truncating a range file empties it; truncating `limit` lifts it.
+it is set. Truncating `dot` empties it, truncating `limit` lifts it, and
+truncating `addr` leaves it as it is (below).
+
+`line:col` is a pardes extension to sam's addresses, the spelling Look
+takes in `file:12:5`: `12:5` is the point at line 12, column 5, and it
+composes like any simple address (`12:5,14:1`, `12:5+#3`). The column is
+in bytes from 1, as Look's is, clamped to the end of the line and snapped
+back to the start of the character it falls in; a line past the end, or
+column 0, is `address out of range`. sam would read `12:5` as a syntax
+error.
 Truncating `data` or `xdata` deletes the range `addr` names and nothing
 else, so a shell's `echo NEW > data` replaces that range, `: > data`
 deletes it, and `>>` inserts at it; only truncating `body` empties the