20110407-1004

7 files changed, 68 insertions, 26 deletions

diff --git a/CHANGES b/CHANGES
index c52e1aaf..eb25ccf7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+20110407
+	fix embarrassingly broken Lists->delete; add Lists->find [issue 257]
+	add some extra explanation to sys-dup(2) about fildes
 20110404
 	update Nt/386/bin
 	/limbo/com.c - count constants in qualifiers, not qualifiers [issue 212, mechiel]
diff --git a/appl/lib/lists.b b/appl/lib/lists.b
index 52e007bb..31d26ddb 100644
--- a/appl/lib/lists.b
+++ b/appl/lib/lists.b
@@ -87,22 +87,30 @@ last[T](l: list of T): T
 	return hd l;
 }
 
-# delete the first instance of x in l
-delete[T](x: T, al: list of T): list of T
+# find instance of x in l, return tail of l from x
+find[T](x: T, l: list of T): list of T
 	for { T =>	eq:	fn(a, b: T): int; }
 {
-	for(l := al; l != nil; l = tl l){
-		if(T.eq(x, hd l)){
-			o: list of T;
-			for(; al != l; al = tl al)
-				o = hd al :: o;
-			l = tl l;
-			for(; o != nil; o = tl o)
-				l = hd o :: l;
+	for(; l != nil; l = tl l)
+		if(T.eq(x, hd l))
 			return l;
-		}
-	}
-	return al;
+	return nil;
+}
+
+# delete the first instance of x in l
+delete[T](x: T, l: list of T): list of T
+	for { T =>	eq:	fn(a, b: T): int; }
+{
+	loc := find(x, l);
+	if(loc == nil)
+		return l;
+	o: list of T;
+	for(; l != loc; l = tl l)
+		o = hd l :: o;
+	l = tl loc;
+	for(; o != nil; o = tl o)
+		l = hd o :: l;
+	return l;
 }
 
 pair[T1, T2](l1: list of T1, l2: list of T2): list of (T1, T2)
diff --git a/dis/lib/lists.dis b/dis/lib/lists.dis
index 58ce79ab..f48dfdd0 100644
--- a/dis/lib/lists.dis
+++ b/dis/lib/lists.dis
diff --git a/include/version.h b/include/version.h
index 66fe5d84..fd472ab7 100644
--- a/include/version.h
+++ b/include/version.h
@@ -1 +1 @@
-#define VERSION	"Fourth Edition (20110406)"
+#define VERSION	"Fourth Edition (20110407)"
diff --git a/man/2/lists b/man/2/lists
index ae52ab49..eebcb964 100644
--- a/man/2/lists
+++ b/man/2/lists
@@ -1,6 +1,6 @@
 .TH LISTS 2
 .SH NAME
-lists: allsat, anysat, append, combine, concat, delete, filter, ismember, last, map, pair, partition, rev, unpair\- list operations
+lists: allsat, anysat, append, combine, concat, delete, filter, find, ismember, last, map, pair, partition, rev, unpair\- list operations
 .SH SYNOPSIS
 .EX
 include "lists.m"
@@ -11,6 +11,8 @@ combine:   fn[T](l1: list of T, l2: list of T): list of T;
 concat:    fn[T](l1: list of T, l2: list of T): list of T;
 delete:    fn[T](x: T, l: list of T): list of T
              for { T => eq:  fn(a, b: T): int; };
+find:      fn[T](x: T, l: list of T): list of T
+             for { T => eq:  fn(a, b: T): int; };
 ismember:  fn[T](x: T, l: list of T): int
              for { T =>  eq: fn(a, b: T): int; };
 last:      fn[T](l: list of T): T;
@@ -38,7 +40,7 @@ Reference types are
 .BR list ,
 .BR module ,
 and
-.BI ref "adt".
+.BI ref " adt".
 None of the operations change their parameter lists: they always return a new list.
 .PP
 First, there is a group of common list operations.
@@ -77,6 +79,23 @@ that returns true (non-zero) if two values of type
 .I T
 are considered equal.
 .PP
+.B Find
+finds the first instance of
+.I x
+in list
+.I l
+and returns the tail of
+.I l
+with
+.I x
+at its head.
+.B Find
+returns nil if there is no
+instance of
+.I x
+in
+.IR l .
+.PP
 .B Ismember
 returns 1 if
 there is an element of
diff --git a/man/2/sys-dup b/man/2/sys-dup
index 7b96b47a..2fd45f7b 100644
--- a/man/2/sys-dup
+++ b/man/2/sys-dup
@@ -21,6 +21,9 @@ or simply `file descriptor' when the context is understood.
 holds an integer-valued file descriptor, the form used
 by the operating system, in a structure that can be reference counted
 and garbage collected.
+When the
+.B FD
+value is reclaimed, the system automatically closes the associated integer file descriptor.
 There are occasions when a program must access the underlying
 integer file descriptor, such as when rearranging the standard input
 and output for a new subprocess.
@@ -47,15 +50,22 @@ If a suitable file descriptor cannot be found,
 returns \-1.
 .PP
 .B Fildes
-uses the integer file descriptor
-.B fd
-to create a new Limbo
-file descriptor, suitable for other
-.B Sys
-module functions.
-It returns
-.B nil
-if it cannot convert
+duplicates the integer file descriptor
+.IR fd ,
+as if by
+.BI "sys->dup(" fd ",-1"),
+and returns a reference to the new descriptor as an
+.B FD
+value,
+making it usable by other functions in
+.BR Sys ,
+such as
+.IR sys-print (2)
+and
+.IR sys-read (2).
+.B Fildes
+returns nil
+if it cannot duplicate
 .IR fd .
 .SH SEE ALSO
 .IR sys-intro (2),
diff --git a/module/lists.m b/module/lists.m
index 5c0678ff..fb6f83ab 100644
--- a/module/lists.m
+++ b/module/lists.m
@@ -11,7 +11,9 @@ Lists: module
 	concat:	fn[T](l: list of T, l2: list of T): list of T;
 	combine:	fn[T](l: list of T, l2: list of T): list of T;
 	reverse:	fn[T](l: list of T): list of T;
-	last:	fn[T](l: list of T): T;
+	last:		fn[T](l: list of T): T;
+	find:		fn[T](x: T, l: list of T): list of T
+		for { T => eq:	fn(a, b: T): int; };
 	delete:	fn[T](x: T, l: list of T): list of T
 		for { T => eq:	fn(a, b: T): int; };
 	pair:	fn[T1, T2](l1: list of T1, l2: list of T2): list of (T1, T2);