=== modified file 'escape.pl'
--- escape.pl	2012-05-17 18:49:59 +0000
+++ escape.pl	2011-11-26 19:12:18 +0000
@@ -1,6 +1,6 @@
 % vim: ft=prolog textwidth=80 tabstop=4 softtabstop=4 shiftwidth=4 expandtab
 
-:- module(escape, [str/2, is_str/1, quoting/4, escape/3]).
+:- module(escape, [str/2, quoting/4, escape/3]).
 
 :- use_module(library(apply)).
 :- use_module(library(lists)).
@@ -34,10 +34,7 @@
 %
 
 str_dlist(X, Joined, End) :-
-    (         is_list(X) -> (  maplist(integer, X)
-                            -> append(X, End, Joined)
-                            ;  throw(not_a_proper_string(X))
-                            )
+    (         is_list(X) -> append(X, End, Joined)
     ;            atom(X) -> name(X, String),
                             append(String, End, Joined)
     ; X = variable(Name) -> Joined = [variable(Name)|End]
@@ -53,8 +50,6 @@
 
 str(X, S) :- str_dlist(X, S, []).
 
-is_str(X) :- atom(X); X=variable(_); X=_+_; X=_+/+_; (is_list(X), maplist(integer, X)).
-
 %%%%%%%%%%%%%%%%%%
 % Shell escaping %
 %%%%%%%%%%%%%%%%%%

=== modified file 'shell.pl'
--- shell.pl	2012-05-17 18:49:59 +0000
+++ shell.pl	2012-05-17 01:48:06 +0000
@@ -1,13 +1,12 @@
 % vim: ft=prolog textwidth=80 tabstop=4 softtabstop=4 shiftwidth=4 expandtab
 
 :- module(shell, [
-    op(600,xfy,($:-)),
-%   op(800,fx,(#)),
+    op(800,xfy,($:-)), ($:-)/2,
+%   op(800,fx,(#)), (#)/1,
     cmd_format/2,
-    cmd_print/1,
     cmds_print/1,
     cmd_repr/1,
-    cmds_repr/1
+    cmds_repr/1,
     ]).
 
 :- use_module(library(apply)).
@@ -32,10 +31,6 @@
     { str(In, Out) },
     prepend(Out).
 
-runnable([_|_]).
-runnable(echo(_)).
-runnable(chroot(_,_)).
-
 cmd_escape_runnable([Arg]) -->
     escape_dcg(Arg).
 cmd_escape_runnable([Arg1,Arg2|Rest]) -->
@@ -49,13 +44,7 @@
 cmd_escape_runnable(chroot(Dir, Args)) -->
     cmd_escape_runnable([Dir +/+ 'chroot.sh'|Args]).
 
-cmd_escape_backticks(Runnable) -->
-    { runnable(Runnable) },
-    prepend("$( "),
-    cmd_escape_runnable(Runnable),
-    prepend(" )").
-
-check_returncode --> prepend(" || exit $?\n").
+check_returncode --> [" || exit $?\n"].
 
 cmd_tokens(Runnable) -->
     cmd_escape_runnable(Runnable),
@@ -73,28 +62,29 @@
     escape_dcg(File),
     check_returncode.
 
-cmd_tokens(Variable = Value) -->
-    str_dcg(Variable),
-    prepend("="),
-    (   { runnable(Value) }
-    ->  prepend("\""),
-        cmd_escape_backticks(Value),
-        prepend("\"")
-    ;   { is_str(Value) }
-    ->  escape_dcg(Value)
-    ;   { Value = Source $:- Default }
-    ->  prepend("\"${"),
-        str_dcg(Source),
-        prepend(":-"),
-        (   { runnable(Default) }
-        ->  cmd_escape_backticks(Default)
-        ;   { is_str(Value) }
-        ->  escape_dcg(Default)
-        ;   throw(incomprehensible_default(Default))
-        ),
-        prepend("}\"")
-    ; throw(incomprehensible_rhs(Value))
-    ),
+cmd_tokens(Variable = Runnable) -->
+    str_dcg(Variable),
+    prepend("=\"$( "),
+    cmd_escape_runnable(Runnable),
+    prepend(" )\""),
+    check_returncode.
+
+cmd_tokens(Variable = Source $:- String) -->
+    str_dcg(Variable),
+    prepend("=\"${"),
+    str_dcg(Source),
+    prepend(":-"),
+    escape_dcg(String)
+    prepend("}\""),
+    check_returncode.
+
+cmd_tokens(Variable = Source $:- Runnable) -->
+    str_dcg(Variable),
+    prepend("=\"${"),
+    str_dcg(Source),
+    prepend(":-$( "),
+    cmd_escape_runnable(String)
+    prepend(" )}\""),
     check_returncode.
 
 cmd_tokens(Variable = array(Runnable)) -->
@@ -104,9 +94,9 @@
     prepend(") )"),
     check_returncode.
 
-cmd_tokens(comment(Text)) -->
+cmd_tokens(# Text) -->
     prepend("\n# "),
-    { str(Text, String) },
+    { str(Text, String) }
     make_comment(String),
     prepend("\n").
 
@@ -117,30 +107,30 @@
 cmd_tokens(run_outarray(List, Var)) --> cmd_tokens(Var = array(List)).
 cmd_tokens(echo_append(String, File)) --> cmd_tokens(echo(String) >> File).
 cmd_tokens(echo_replace(String, File)) --> cmd_tokens(echo(String) > File).
-% cmd_tokens(comment(Text)) --> cmd_tokens(# Text).
+cmd_tokens(comment(Text)) --> cmd_tokens(# Text).
 
 make_comment([         ]) --> [].
 make_comment([Char|Rest]) :-
    (  { [Char] = "\n" }
-   -> prepend("\n# ")
+   -> prepend("\n# "),
    ;  prepend(Char)
    ),
    make_comment(Rest).
 
-cmd_format(Cmd, String) :- phrase(cmd_tokens(Cmd), String, []).
-
-cmd_print(Cmd) :-
-    cmd_format(Cmd, String), !,
-    name(Name, String),
-    write(Name).
+cmd_format(Cmd, String) :- phrase(cmd_tokens(Cmd), [], String).
 
 cmds_print(Commands) :-
-    maplist(cmd_print, Commands).
+    maplist(cmd_format, Commands, Lines), !,
+    str_join("\n", Lines, String),
+    name(Name,String),
+    nl,
+    write(Name),
+    nl.
 
-print_solution(String) :-
-    name(Text, String),
+print_solution(Solution) :-
+    str_join('\n', Solution, String), name(Text, String),
     write(Text),
-    nl.
+    nl, nl.
 
 cmd_repr(Command) :-
     write('representation of: '), writeq(Command), write(' ::'), nl,