3 files changed, 123 insertions, 9 deletions
diff --git a/cppawk-cons.1 b/cppawk-cons.1
index 86393c1..64939af 100644
--- a/cppawk-cons.1
+++ b/cppawk-cons.1
@@ -107,7 +107,7 @@ cons \- Lisp-like data representation and control flow macros
 
   \fI// Field/list conversion\fP
 
-  fields()          \fI// convert Awk positional fields to list\fP
+  fields([\fIi \fP[, \fIn\fP]]) \fI// convert Awk positional fields to list\fP
   set_fields(\fIx\fP)     \fI// set Awk positional fields from list x\fP
 
   \fI// list iteration\fP
@@ -1970,10 +1970,10 @@ or unboxed objects.
 .bk
 .SS Functions \fIfields\fP and \fIset_fields\fP
 .bk
-Syntax:
+.B Syntax:
 
 .ft B
-  fields()
+  fields([\fIi \fP[, \fIn\fP]])
   set_fields(\fIx\fP)
 .ft R
 
@@ -1981,10 +1981,33 @@ Syntax:
 
 The
 .B fields
-function returns a list of the current values of the Awk positional fields from
-.B $1
+function converts a range of the current values of the Awk positional fields
+into a list, which it returns.  The function turns its arguments into an
+abstract range of field indices to visit. Any field numbers which lie outside
+of the valid range 1 to
+.B NF
+are clipped from this range, and the remaining fields are accessed and included
+in the returned list.
+
+The
+.I i
+parameter indicates the starting field. If an argument isn't given,
+it defaults to 1. It may be zero, or negative. Note that the record
+.B $0
+isn't considered to be a field; this function does not access
+.BR $0 .
+
+The
+.I n
+argument gives the number of fields to include in the list, starting at
+.IR i .
+If omitted, it defaults to including all of the fields from
+.I i
 to
-.BR $NF .
+.BR NF .
+If
+.B n
+is less than 1, the empty list is returned.
 
 The
 .B set_fields
@@ -2013,6 +2036,12 @@ contains boxed values, then those boxed values become fields.
 
   fields() -> ("the" "quick" "brown" "fox")
 
+  \fI// range [-1, 2] is clipped to [1, 2]\fB
+  fields(-1, 4) -> ("the" "quick")
+
+  \fI// range [3, 10] is clipped to [3, 4]\fB
+  fields(3, 7) -> ("brown" "fox")
+
   set_fields(list(1, cons(1, 2), "foo", box_str("foo")))
 
   \fI// this loop now prints:\fP
diff --git a/cppawk-include/cons-priv.h b/cppawk-include/cons-priv.h
index 6ca2c05..172f20f 100644
--- a/cppawk-include/cons-priv.h
+++ b/cppawk-include/cons-priv.h
@@ -336,12 +336,33 @@ function __keys(__array,
 }
 
 
-function __fields(  __tmp, __i, __val)
+function __fields(__start, __count,
+                  __tmp, __end, __val)
 {
+  if (!__present(__start))
+    __start = 1
+
+  if (!__present(__count))
+    __count = NF - __start + 1
+
+  if (__count < 1)
+    return __nil
+
+  __end = __start + __count - 1
+
+  if (__end > NF)
+    __end = NF
+
+  if (__start < 1)
+    __start = 1
+
+  if (__start > __end)
+    return __nil
+
   __tmp = __list_begin()
 
-  __dofields (__i, __val)
-    __tmp = __list_add(__tmp, __val)
+  for (; __start <= __end; __start++)
+    __tmp = __list_add(__tmp, $(__start))
 
   return __list_end(__tmp)
 }
diff --git a/testcases-cons b/testcases-cons
index e945478..e5342c0 100644
--- a/testcases-cons
+++ b/testcases-cons
@@ -873,3 +873,67 @@ BEGIN {
 (0 1 2 3 4)
 (0 1 4 9 16)
 (0 1 3 6 10)
+--
+45:
+$cppawk '
+#include <cons.h>
+
+BEGIN {
+  $0 = "the quick brown fox"
+  print sexp(fields(1))
+  print sexp(fields(2))
+  print sexp(fields(3))
+  print sexp(fields(4))
+  print sexp(fields(5))
+  print sexp(fields(1, 0))
+  print sexp(fields(2, 0))
+  print sexp(fields(3, 0))
+  print sexp(fields(4, 0))
+  print sexp(fields(5, 0))
+  print sexp(fields(1, 1))
+  print sexp(fields(2, 1))
+  print sexp(fields(3, 1))
+  print sexp(fields(4, 1))
+  print sexp(fields(5, 1))
+}'
+:
+("the" "quick" "brown" "fox")
+("quick" "brown" "fox")
+("brown" "fox")
+("fox")
+nil
+nil
+nil
+nil
+nil
+nil
+("the")
+("quick")
+("brown")
+("fox")
+nil
+--
+46:
+$cppawk '
+#include <cons.h>
+
+BEGIN {
+  $0 = "the quick brown fox"
+  print sexp(fields(-10, 20))
+  print sexp(fields(-1, 2))
+  print sexp(fields(0, 2))
+  print sexp(fields(l, 2))
+  print sexp(fields(2, 2))
+  print sexp(fields(3, 2))
+  print sexp(fields(4, 2))
+  print sexp(fields(5, 2))
+}'
+:
+("the" "quick" "brown" "fox")
+nil
+("the")
+("the" "quick")
+("quick" "brown")
+("brown" "fox")
+("fox")
+nil