From f1e232c9812e570943f76bc9a1e6e3577659c2e9 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Sun, 29 Jul 2012 10:14:54 -0700
Subject: [PATCH] prettyprint: print unprintables by hex escaping.

---
 basis/prettyprint/backend/backend.factor   | 8 +++++---
 basis/prettyprint/prettyprint-tests.factor | 4 ++++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/basis/prettyprint/backend/backend.factor b/basis/prettyprint/backend/backend.factor
index b43387d93e..1d03707e67 100644
--- a/basis/prettyprint/backend/backend.factor
+++ b/basis/prettyprint/backend/backend.factor
@@ -96,7 +96,7 @@ M: f pprint* drop \ f pprint-word ;
     [ effect>string ] [ effect-style ] bi styled-text ;
 
 ! Strings
-: ch>ascii-escape ( ch -- str )
+: ch>ascii-escape ( ch -- ch' ? )
     H{
         { CHAR: \a CHAR: a  }
         { CHAR: \e CHAR: e  }
@@ -106,10 +106,12 @@ M: f pprint* drop \ f pprint-word ;
         { CHAR: \0 CHAR: 0  }
         { CHAR: \\ CHAR: \\ }
         { CHAR: \" CHAR: \" }
-    } at ;
+    } ?at ; inline
 
 : unparse-ch ( ch -- )
-    dup ch>ascii-escape [ "\\" % ] [ ] ?if , ;
+    ch>ascii-escape [ "\\" % , ] [
+        dup 32 < [ dup 16 < "\\x0" "\\x" ? % >hex % ] [ , ] if
+    ] if ;
 
 : do-string-limit ( str -- trimmed )
     string-limit? get [
diff --git a/basis/prettyprint/prettyprint-tests.factor b/basis/prettyprint/prettyprint-tests.factor
index 79d0a664c1..17cedcc7e4 100644
--- a/basis/prettyprint/prettyprint-tests.factor
+++ b/basis/prettyprint/prettyprint-tests.factor
@@ -40,6 +40,10 @@ unit-test
 [ "\e" unparse ]
 unit-test
 
+[ "\"\\x01\"" ]
+[ 1 1string unparse ]
+unit-test
+
 [ "f" ] [ f unparse ] unit-test
 [ "t" ] [ t unparse ] unit-test