added comments about negative indexes in _nth, _tail and _head algorithms

[SVN r33255]

include/boost/algorithm/string/erase.hpp

@@ -387,6 +387,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input
 
@@ -433,6 +434,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for. 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
         */
         template<typename SequenceT, typename RangeT>
         inline void erase_nth( 
@@ -459,6 +461,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for.
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Loc A locale used for case insensitive comparison
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input
@@ -508,6 +511,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for. 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Loc A locale used for case insensitive comparison
         */
         template<typename SequenceT, typename RangeT>
@@ -675,7 +679,9 @@ namespace boost {
 
             \param Output An output iterator to which the result will be copied
             \param Input An input string
-            \param N Length of the head
+            \param N Length of the head.
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input
 
@@ -719,6 +725,8 @@ namespace boost {
 
             \param Input An input string
             \param N Length of the head
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
         */
         template<typename SequenceT>
         inline void erase_head( 
@@ -743,7 +751,9 @@ namespace boost {
 
             \param Output An output iterator to which the result will be copied
             \param Input An input string
-            \param N Length of the head
+            \param N Length of the head.                 
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input
             
@@ -787,6 +797,8 @@ namespace boost {
 
             \param Input An input string
             \param N Length of the head
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
         */
         template<typename SequenceT>
         inline void erase_tail( 

include/boost/algorithm/string/find.hpp

@@ -176,6 +176,7 @@ namespace boost {
             \param Input A string which will be searched.
             \param Search A substring to be searched for.
             \param Nth An index (zero-indexed) of the match to be found.
+                For negative N, the matches are counted from the end of string.
             \return 
                 An \c iterator_range delimiting the match. 
                 Returned iterator is either \c Range1T::iterator or 
@@ -196,12 +197,13 @@ namespace boost {
 
         //! Find n-th algorithm ( case insensitive ).
         /*!
-            Search for the n-th (zero-indexed) occurence of the substring in the 
+            Search for the n-th (zero-indexed) occurrence of the substring in the 
             input. Searching is case insensitive.
             
             \param Input A string which will be searched.
             \param Search A substring to be searched for.
             \param Nth An index (zero-indexed) of the match to be found. 
+                For negative N, the matches are counted from the end of string.
             \param Loc A locale used for case insensitive comparison
             \return 
                 An \c iterator_range delimiting the match. 
@@ -235,6 +237,8 @@ namespace boost {
 
             \param Input An input string
             \param N Length of the head
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \return 
                 An \c iterator_range delimiting the match. 
                 Returned iterator is either \c Range1T::iterator or 
@@ -263,7 +267,9 @@ namespace boost {
             to be the tail.
 
             \param Input An input string
-            \param N Length of the tail
+            \param N Length of the tail. 
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \return 
                 An \c iterator_range delimiting the match. 
                 Returned iterator is either \c RangeT::iterator or 

include/boost/algorithm/string/predicate.hpp

@@ -393,7 +393,6 @@ namespace boost {
 
              \param Arg1 First argument 
              \param Arg2 Second argument
-             \param Pred Comparison predicate
              \return The result of the test
 
              \note This function provides the strong exception-safety guarantee

include/boost/algorithm/string/replace.hpp

@@ -428,6 +428,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Format A substitute string
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input
@@ -478,6 +479,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Format A substitute string
         */
         template<typename SequenceT, typename Range1T, typename Range2T>
@@ -507,6 +509,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Format A substitute string
             \param Loc A locale used for case insensitive comparison
             \return An output iterator pointing just after the last inserted character or
@@ -561,6 +564,7 @@ namespace boost {
             \param Input An input string
             \param Search A substring to be searched for 
             \param Nth An index of the match to be replaced. The index is 0-based.
+                For negative N, matches are counted from the end of string.
             \param Format A substitute string
             \param Loc A locale used for case insensitive comparison
         */
@@ -745,7 +749,9 @@ namespace boost {
             
             \param Output An output iterator to which the result will be copied
             \param Input An input string
-            \param N Length of the head
+            \param N Length of the head.
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \param Format A substitute string
             \return An output iterator pointing just after the last inserted character or
                 a modified copy of the input  
@@ -793,7 +799,9 @@ namespace boost {
             considered to be the head. The input sequence is modified in-place.
 
             \param Input An input string
-            \param N Length of the head
+            \param N Length of the head.
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \param Format A substitute string
         */
         template<typename SequenceT, typename RangeT>
@@ -821,7 +829,9 @@ namespace boost {
 
             \param Output An output iterator to which the result will be copied
             \param Input An input string
-            \param N Length of the tail
+            \param N Length of the tail.
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \param Format A substitute string
             \return An output iterator pointing just after the last inserted character or
                     a modified copy of the input   
@@ -869,7 +879,9 @@ namespace boost {
             considered to be the tail. The input sequence is modified in-place.
 
             \param Input An input string
-            \param N Length of the tail
+            \param N Length of the tail.
+                For N>=0, at most N characters are extracted.
+                For N<0, size(Input)-|N| characters are extracted.
             \param Format A substitute string
         */
         template<typename SequenceT, typename RangeT>