stdlib/strings: Detached the Text block from Collection.
[nit.git] / lib / standard / string.nit
index e707454..de11bac 100644 (file)
 #
 # This file is free software, which comes along with NIT.  This software is
 # distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
-# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A 
+# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A
 # PARTICULAR PURPOSE.  You can modify it is you want,  provided this header
 # is kept unaltered, and a notification of the changes is added.
 # You  are  allowed  to  redistribute it and sell it, alone or is a part of
 # another product.
 
 # Basic manipulations of strings of characters
-package string
+module string
 
+import math
 intrude import collection # FIXME should be collection::array
-import hash
+
+`{
+#include <stdio.h>
+`}
 
 ###############################################################################
 # String                                                                      #
 ###############################################################################
 
-# Common subclass for String and Buffer
-abstract class AbstractString
-       super AbstractArrayRead[Char]
+# High-level abstraction for all text representations
+abstract class Text
 
-       readable private var _items: NativeString
+       # Gets a view on the chars of the Text object
+       fun chars: StringCharView is abstract
 
-       redef fun [](index) do return _items[index]
+       # Number of characters contained in self.
+       fun length: Int is abstract
 
        # Create a substring.
        #
-       # "abcd".substring(1, 2)        # --> "bc"
-       # "abcd".substring(-1, 2)       # --> "a"
-       # "abcd".substring(1, 0)     # --> ""
-       # "abcd".substring(2, 5)     # --> "cd"
-       fun substring(from: Int, count: Int): String
+       #     assert "abcd".substring(1, 2)      ==  "bc"
+       #     assert "abcd".substring(-1, 2)     ==  "a"
+       #     assert "abcd".substring(1, 0)      ==  ""
+       #     assert "abcd".substring(2, 5)      ==  "cd"
+       #
+       # A `from` index < 0 will be replaced by 0.
+       # Unless a `count` value is > 0 at the same time.
+       # In this case, `from += count` and `count -= from`.
+       fun substring(from: Int, count: Int): String is abstract
+
+       # Is the current Text empty (== "")
+       #       assert "".is_empty
+       #       assert not "foo".is_empty
+       fun is_empty: Bool do return self.length == 0
+
+       # Gets the first char of the Text
+       #
+       # DEPRECATED : Use self.chars.first instead
+       fun first: Char do return self.chars[0]
+
+       # Access a character at `index` in the string.
+       #
+       #     assert "abcd"[2]         == 'c'
+       #
+       # DEPRECATED : Use self.chars.[] instead
+       fun [](index: Int): Char do return self.chars[index]
+
+       # Gets the index of the first occurence of 'c'
+       #
+       # Returns -1 if not found
+       #
+       # DEPRECATED : Use self.chars.index_of instead
+       fun index_of(c: Char): Int
        do
-               assert count >= 0
-               count += from
-               if from < 0 then from = 0
-               if count > length then count = length
-               if from < count then
-                       var r = new Buffer.with_capacity(count - from)
-                       while from < count do
-                               r.push(_items[from])
-                               from += 1
-                       end
-                       return r.to_s
-               else
-                       return ""
+               return index_of_from(c, 0)
+       end
+
+       # Gets the last char of self
+       #
+       # DEPRECATED : Use self.chars.last instead
+       fun last: Char do return self.chars[length-1]
+
+       # Gets the index of the first occurence of ´c´ starting from ´pos´
+       #
+       # Returns -1 if not found
+       #
+       # DEPRECATED : Use self.chars.index_of_from instead
+       fun index_of_from(c: Char, pos: Int): Int
+       do
+               var iter = self.chars.iterator_from(pos)
+               while iter.is_ok do
+                       if iter.item == c then return iter.index
+               end
+               return -1
+       end
+
+       # Gets the last index of char ´c´
+       #
+       # Returns -1 if not found
+       #
+       # DEPRECATED : Use self.chars.last_index_of instead
+       fun last_index_of(c: Char): Int
+       do
+               return last_index_of_from(c, length - 1)
+       end
+
+       # The index of the last occurrence of an element starting from pos (in reverse order).
+       # Example :
+       #               assert "/etc/bin/test/test.nit".last_index_of_from('/', length-1) == 13
+       #               assert "/etc/bin/test/test.nit".last_index_of_from('/', 12) == 8
+       #
+       # Returns -1 if not found
+       #
+       # DEPRECATED : Use self.chars.last_index_of_from instead
+       fun last_index_of_from(item: Char, pos: Int): Int
+       do
+               var iter = self.chars.reverse_iterator_from(pos)
+               while iter.is_ok do
+                       if iter.item == item then return iter.index
+                       iter.next
                end
+               return -1
        end
 
-       # Create a substring from `self' beginning at the 'from' position
+       # Gets an iterator on the chars of self
        #
-       # "abcd".substring(1)   # --> "bcd"
-       # "abcd".substring(-1)  # --> "abcd"
-       # "abcd".substring(2)     # --> "cd"
+       # DEPRECATED : Use self.chars.iterator instead
+       fun iterator: Iterator[Char]
+       do
+               return self.chars.iterator
+       end
+
+       # Is 'c' contained in self ?
+       #
+       # DEPRECATED : Use self.chars.has instead
+       fun has(c: Char): Bool
+       do
+               return self.chars.has(c)
+       end
+
+       # Gets an Array containing the chars of self
+       #
+       # DEPRECATED : Use self.chars.to_a instead
+       fun to_a: Array[Char] do return chars.to_a
+
+       # Create a substring from `self` beginning at the `from` position
+       #
+       #     assert "abcd".substring_from(1)    ==  "bcd"
+       #     assert "abcd".substring_from(-1)   ==  "abcd"
+       #     assert "abcd".substring_from(2)    ==  "cd"
+       #
+       # As with substring, a `from` index < 0 will be replaced by 0
        fun substring_from(from: Int): String
        do
                assert from < length
                return substring(from, length - from)
        end
 
-       # Does self have a substring 'str' starting from position 'pos
+       # Does self have a substring `str` starting from position `pos`?
        #
-       # "abcd".has_substring("bc",1)  # --> true
-       # "abcd".has_substring("bc",2)  # --> false
+       #     assert "abcd".has_substring("bc",1)            ==  true
+       #     assert "abcd".has_substring("bc",2)            ==  false
        fun has_substring(str: String, pos: Int): Bool
        do
-               var itsindex = str.length - 1
-               var myindex = pos + itsindex
-               var myitems = _items
-               var itsitems = str._items
-               if myindex > length or itsindex > myindex  then return false
-               var its_index_from = str._index_from
-               itsindex += its_index_from
-               while itsindex >= its_index_from do
-                       if myitems[myindex] != itsitems[itsindex] then return false
-                       myindex -= 1
-                       itsindex -= 1
+               var myiter = self.chars.iterator_from(pos)
+               var itsiter = str.iterator
+               while myiter.is_ok and itsiter.is_ok do
+                       if myiter.item != itsiter.item then return false
+                       myiter.next
+                       itsiter.next
                end
+               if itsiter.is_ok then return false
                return true
        end
 
-       # Is this string prefixed by 'prefix'
+       # Is this string prefixed by `prefix`?
        #
-       # "abc".is_prefix("abcd")       # --> true
-       # "bc".is_prefix("abcd")        # --> false
+       #     assert "abcd".has_prefix("ab")           ==  true
+       #     assert "abcbc".has_prefix("bc")          ==  false
+       #     assert "ab".has_prefix("abcd")           ==  false
        fun has_prefix(prefix: String): Bool do return has_substring(prefix,0)
 
-       # Is this string suffixed by 'suffix'
+       # Is this string suffixed by `suffix`?
        #
-       # "abcd".has_suffix("abc")      # --> false
-       # "abcd".has_suffix("bcd")      # --> true
+       #     assert "abcd".has_suffix("abc")        ==  false
+       #     assert "abcd".has_suffix("bcd")        ==  true
        fun has_suffix(suffix: String): Bool do return has_substring(suffix, length - suffix.length)
 
-       # If `self' contains only digits, return the corresponding integer
+       # If `self` contains only digits, return the corresponding integer
+       #
+       #     assert "123".to_i        == 123
+       #     assert "-1".to_i         == -1
        fun to_i: Int
        do
                # Shortcut
                return to_s.to_cstring.atoi
        end
 
-       # If `self' contains a float, return the corresponding float
+       # If `self` contains a float, return the corresponding float
+       #
+       #     assert "123".to_f        == 123.0
+       #     assert "-1".to_f         == -1.0
+       #     assert "-1.2e-3".to_f    == -0.0012
        fun to_f: Float
        do
                # Shortcut
                return to_s.to_cstring.atof
        end
 
-       # If `self' contains only digits and alpha <= 'f', return the corresponding integer.
+       # If `self` contains only digits and alpha <= 'f', return the corresponding integer.
        fun to_hex: Int do return a_to(16)
 
-       # If `self' contains only digits and letters, return the corresponding integer in a given base
+       # If `self` contains only digits and letters, return the corresponding integer in a given base
+       #
+       #     assert "120".a_to(3)     == 15
        fun a_to(base: Int) : Int
        do
                var i = 0
                var neg = false
 
-               for c in self
+               for c in self.chars
                do
                        var v = c.to_i
                        if v > base then
@@ -142,11 +238,16 @@ abstract class AbstractString
                end
        end
 
-       # Returns true if the string contains only Numeric values (and one "," or one "." character)
+       # Returns `true` if the string contains only Numeric values (and one "," or one "." character)
+       #
+       #     assert "123".is_numeric  == true
+       #     assert "1.2".is_numeric  == true
+       #     assert "1,2".is_numeric  == true
+       #     assert "1..2".is_numeric == false
        fun is_numeric: Bool
        do
                var has_point_or_comma = false
-               for i in self
+               for i in self.chars
                do
                        if not i.is_numeric
                        then
@@ -161,42 +262,177 @@ abstract class AbstractString
                return true
        end
 
-       # A upper case version of `self'
+       # A upper case version of `self`
+       #
+       #     assert "Hello World!".to_upper     == "HELLO WORLD!"
        fun to_upper: String
        do
                var s = new Buffer.with_capacity(length)
-               for i in self do s.add(i.to_upper)
+               for i in self.chars do s.add(i.to_upper)
                return s.to_s
        end
 
-       # A lower case version of `self'
+       # A lower case version of `self`
+       #
+       #     assert "Hello World!".to_lower     == "hello world!"
        fun to_lower : String
        do
                var s = new Buffer.with_capacity(length)
-               for i in self do s.add(i.to_lower)
+               for i in self.chars do s.add(i.to_lower)
                return s.to_s
        end
 
        # Trims trailing and preceding white spaces
        # A whitespace is defined as any character which ascii value is less than or equal to 32
+       #
+       #     assert "  Hello  World !  ".trim   == "Hello  World !"
+       #     assert "\na\nb\tc\t".trim          == "a\nb\tc"
        fun trim: String
        do
-               if self._length == 0 then return self.to_s
+               if self.length == 0 then return self.to_s
                # find position of the first non white space char (ascii < 32) from the start of the string
                var start_pos = 0
-               while self[start_pos].ascii <= 32 do
+               while self.chars[start_pos].ascii <= 32 do
                        start_pos += 1
-                       if start_pos == _length then return ""
+                       if start_pos == length then return ""
                end
                # find position of the first non white space char from the end of the string
                var end_pos = length - 1
-               while self[end_pos].ascii <= 32 do
+               while self.chars[end_pos].ascii <= 32 do
                        end_pos -= 1
-                       if end_pos == start_pos then return self[start_pos].to_s
+                       if end_pos == start_pos then return self.chars[start_pos].to_s
                end
                return self.substring(start_pos, end_pos - start_pos + 1)
        end
 
+       # Mangle a string to be a unique string only made of alphanumeric characters
+       fun to_cmangle: String
+       do
+               var res = new Buffer
+               var underscore = false
+               for c in self.chars do
+                       if (c >= 'a' and c <= 'z') or (c >='A' and c <= 'Z') then
+                               res.add(c)
+                               underscore = false
+                               continue
+                       end
+                       if underscore then
+                               res.append('_'.ascii.to_s)
+                               res.add('d')
+                       end
+                       if c >= '0' and c <= '9' then
+                               res.add(c)
+                               underscore = false
+                       else if c == '_' then
+                               res.add(c)
+                               underscore = true
+                       else
+                               res.add('_')
+                               res.append(c.ascii.to_s)
+                               res.add('d')
+                               underscore = false
+                       end
+               end
+               return res.to_s
+       end
+
+       # Escape " \ ' and non printable characters using the rules of literal C strings and characters
+       #
+       #     assert "abAB12<>&".escape_to_c         == "abAB12<>&"
+       #     assert "\n\"'\\".escape_to_c         == "\\n\\\"\\'\\\\"
+       fun escape_to_c: String
+       do
+               var b = new Buffer
+               for c in self.chars do
+                       if c == '\n' then
+                               b.append("\\n")
+                       else if c == '\0' then
+                               b.append("\\0")
+                       else if c == '"' then
+                               b.append("\\\"")
+                       else if c == '\'' then
+                               b.append("\\\'")
+                       else if c == '\\' then
+                               b.append("\\\\")
+                       else if c.ascii < 32 then
+                               b.append("\\{c.ascii.to_base(8, false)}")
+                       else
+                               b.add(c)
+                       end
+               end
+               return b.to_s
+       end
+
+       # Escape additionnal characters
+       # The result might no be legal in C but be used in other languages
+       #
+       #     assert "ab|\{\}".escape_more_to_c("|\{\}") == "ab\\|\\\{\\\}"
+       fun escape_more_to_c(chars: String): String
+       do
+               var b = new Buffer
+               for c in escape_to_c do
+                       if chars.chars.has(c) then
+                               b.add('\\')
+                       end
+                       b.add(c)
+               end
+               return b.to_s
+       end
+
+       # Escape to c plus braces
+       #
+       #     assert "\n\"'\\\{\}".escape_to_nit      == "\\n\\\"\\'\\\\\\\{\\\}"
+       fun escape_to_nit: String do return escape_more_to_c("\{\}")
+
+       # Return a string where Nit escape sequences are transformed.
+       #
+       # Example:
+       #     var s = "\\n"
+       #     assert s.length        ==  2
+       #     var u = s.unescape_nit
+       #     assert u.length        ==  1
+       #     assert u[0].ascii      ==  10 # (the ASCII value of the "new line" character)
+       fun unescape_nit: String
+       do
+               var res = new Buffer.with_capacity(self.length)
+               var was_slash = false
+               for c in self do
+                       if not was_slash then
+                               if c == '\\' then
+                                       was_slash = true
+                               else
+                                       res.add(c)
+                               end
+                               continue
+                       end
+                       was_slash = false
+                       if c == 'n' then
+                               res.add('\n')
+                       else if c == 'r' then
+                               res.add('\r')
+                       else if c == 't' then
+                               res.add('\t')
+                       else if c == '0' then
+                               res.add('\0')
+                       else
+                               res.add(c)
+                       end
+               end
+               return res.to_s
+       end
+
+end
+
+# Common subclass for String and Buffer
+abstract class AbstractString
+       super Text
+
+       readable private var _items: NativeString
+
+       redef readable private var _length: Int
+
+       init do end
+
        redef fun output
        do
                var i = 0
@@ -207,6 +443,82 @@ abstract class AbstractString
        end
 end
 
+# Abstract class for the SequenceRead compatible
+# views on String and Buffer objects
+abstract class StringCharView
+       super SequenceRead[Char]
+
+       type SELFTYPE: Text
+
+       private var target: SELFTYPE
+
+       private init(tgt: SELFTYPE)
+       do
+               target = tgt
+       end
+
+       redef fun is_empty do return target.is_empty
+
+       redef fun length do return target.length
+
+       redef fun iterator: IndexedIterator[Char] do return self.iterator_from(0)
+
+       # Gets a new Iterator starting at position `pos`
+       #
+       # Ex :
+       #       var iter = "abcd".iterator_from(2)
+       #       while iter.is_ok do
+       #               printn iter.item
+       #               iter.next
+       #       end
+       #
+       # Outputs : cd
+       fun iterator_from(pos: Int): IndexedIterator[Char] is abstract
+
+       # Gets an iterator starting at the end and going backwards
+       #
+       # Ex :
+       #       var reviter = "now step live...".reverse_iterator
+       #       while reviter.is_ok do
+       #               printn reviter.item
+       #               reviter.next
+       #       end
+       #
+       # Outputs : ...evil pets won
+       fun reverse_iterator: IndexedIterator[Char] do return self.reverse_iterator_from(self.length - 1)
+
+       # Gets an iterator on the chars of self starting from `pos`
+       #
+       # Ex :
+       #       var iter = "abcd".reverse_iterator_from(1)
+       #       while iter.is_ok do
+       #               printn iter.item
+       #               iter.next
+       #       end
+       #
+       # Outputs : ba
+       fun reverse_iterator_from(pos: Int): IndexedIterator[Char] is abstract
+
+       redef fun has(c: Char): Bool
+       do
+               for i in self do
+                       if i == c then return true
+               end
+               return false
+       end
+
+end
+
+# View on Buffer objects, extends Sequence
+# for mutation operations
+abstract class BufferCharView
+       super StringCharView
+       super Sequence[Char]
+
+       redef type SELFTYPE: Buffer
+
+end
+
 # Immutable strings of characters.
 class String
        super Comparable
@@ -221,12 +533,12 @@ class String
        # Indes in _items of the last item of the string
        readable var _index_to: Int
 
+       redef var chars: StringCharView = new FlatStringCharView(self)
+
        ################################################
        #       AbstractString specific methods        #
        ################################################
 
-       # Access a character at index in String
-       #
        redef fun [](index) do
                assert index >= 0
                # Check that the index (+ index_from) is not larger than indexTo
@@ -235,17 +547,6 @@ class String
                return _items[index + _index_from]
        end
 
-       # Create a substring.
-       #
-       # "abcd".substring(1, 2)        # --> "bc"
-       # "abcd".substring(-1, 2)       # --> "a"
-       # "abcd".substring(1, 0)    # --> ""
-       # "abcd".substring(2, 5)    # --> "cd"
-       #
-       # A "from" index < 0 will be replaced by 0
-       # Unless a count value is > 0 at the same time
-       # In this case, from += count and count -= from
-       #
        redef fun substring(from: Int, count: Int): String
        do
                assert count >= 0
@@ -258,57 +559,16 @@ class String
 
                var realFrom = _index_from + from
 
-               if (realFrom + count) > _index_to then return new String.from_substring(realFrom, _index_to, _items)
+               if (realFrom + count) > _index_to then return new String.with_infos(_items, _index_to - realFrom + 1, realFrom, _index_to)
 
                if count == 0 then return ""
 
-               return new String.from_substring(realFrom, realFrom + count - 1, _items)
-       end
+               var to = realFrom + count - 1
 
-       # Create a substring from `self' beginning at the 'from' position
-       #
-       # "abcd".substring_from(1)      # --> "bcd"
-       # "abcd".substring_from(-1)     # --> "abcd"
-       # "abcd".substring_from(2)  # --> "cd"
-       #
-       # As with substring, a "from" index < 0 will be replaced by 0
-       #
-       redef fun substring_from(from: Int): String
-       do
-               if from > _length then return ""
-               if from < 0 then from = 0
-               return substring(from, _length)
+               return new String.with_infos(_items, to - realFrom + 1, realFrom, to)
        end
 
-       # Does self have a substring 'str' starting from position 'pos
-       #
-       # "abcd".has_substring("bc",1)  # --> true
-       # "abcd".has_substring("bc",2)  # --> false
-       redef fun has_substring(str: String, pos: Int): Bool
-       do
-               var itsindex = str._length - 1
-
-               var myindex = pos + itsindex
-               var myitems = _items
-
-               var itsitems = str._items
-
-               if myindex > _length or itsindex > myindex then return false
 
-               var itsindexfrom = str.index_from
-               itsindex += itsindexfrom
-               myindex += index_from
-
-               while itsindex >= itsindexfrom do
-                       if myitems[myindex] != itsitems[itsindex] then return false
-                       myindex -= 1
-                       itsindex -= 1
-               end
-
-               return true
-       end
-
-       # A upper case version of `self'
        redef fun to_upper: String
        do
                var outstr = calloc_string(self._length + 1)
@@ -326,10 +586,9 @@ class String
 
                outstr[self.length] = '\0'
 
-               return new String.with_native(outstr, self._length)
+               return outstr.to_s_with_length(self._length)
        end
 
-       # A lower case version of `self'
        redef fun to_lower : String
        do
                var outstr = calloc_string(self._length + 1)
@@ -347,7 +606,7 @@ class String
 
                outstr[self.length] = '\0'
 
-               return new String.with_native(outstr, self._length)
+               return outstr.to_s_with_length(self._length)
        end
 
        redef fun trim: String
@@ -384,53 +643,17 @@ class String
        #              String Specific Methods           #
        ##################################################
 
-       # Creates a String object as a substring of another String
-       #
-       # From : index to start at
-       #
-       # To : Index to stop at (from + count -1)
-       #
-       private init from_substring(from: Int, to: Int, internalString: NativeString)
+       private init with_infos(items: NativeString, len: Int, from: Int, to: Int)
        do
-               _items = internalString
+               self._items = items
+               _length = len
                _index_from = from
                _index_to = to
-               _length = to - from + 1
-       end
-
-       # Create a new string from a given char *.
-       init with_native(nat: NativeString, size: Int)
-       do
-               assert size >= 0
-               _items = nat
-               _length = size
-               _index_from = 0
-               _index_to = _length - 1
-       end
-
-       # Create a new string from a null terminated char *.
-       init from_cstring(str: NativeString)
-       do
-               with_native(str,str.cstring_length)
-       end
-
-       # Creates a new Nit String from an existing CString
-       # Pretty much equals to from_cstring but copies instead
-       # of passing a reference
-       # Avoids manual/automatic dealloc problems when dealing with native C code
-       init copy_from_native(str: NativeString)
-       do
-               var temp_length = str.cstring_length
-               var new_str = calloc_string(temp_length + 1)
-               str.copy_to(new_str, temp_length, 0, 0)
-               new_str[temp_length] = '\0'
-               with_native(new_str, temp_length)
        end
 
        # Return a null terminated char *
        fun to_cstring: NativeString
        do
-               #return items
                if _index_from > 0 or _index_to != items.cstring_length - 1 then
                        var newItems = calloc_string(_length + 1)
                        self.items.copy_to(newItems, _length, _index_from, 0)
@@ -442,7 +665,7 @@ class String
 
        redef fun ==(other)
        do
-               if not other isa String or other is null then return false
+               if not other isa String then return false
 
                if self.object_id == other.object_id then return true
 
@@ -468,7 +691,8 @@ class String
        end
 
        # The comparison between two strings is done on a lexicographical basis
-       # Eg : "aa" < "b" => true
+       #
+       #     assert ("aa" < "b")      ==  true
        redef fun <(other)
        do
                if self.object_id == other.object_id then return false
@@ -500,31 +724,34 @@ class String
                        curr_id_other += 1
                end
 
-               if my_length != its_length then
-                       if my_length < its_length then return true
-                       return false
-               end
-
-               return false
+               return my_length < its_length
        end
 
-       # The concatenation of `self' with `r'
+       # The concatenation of `self` with `s`
+       #
+       #     assert "hello " + "world!"         == "hello world!"
        fun +(s: String): String
        do
                var my_length = self._length
                var its_length = s._length
 
+               var total_length = my_length + its_length
+
                var target_string = calloc_string(my_length + its_length + 1)
 
                self._items.copy_to(target_string, my_length, _index_from, 0)
                s._items.copy_to(target_string, its_length, s._index_from, my_length)
 
-               target_string[my_length + its_length] = '\0'
+               target_string[total_length] = '\0'
 
-               return new String.with_native(target_string, my_length + its_length)
+               return target_string.to_s_with_length(total_length)
        end
 
-       # i repetitions of self
+       # `i` repetitions of `self`
+       #
+       #     assert "abc"*3           == "abcabcabc"
+       #     assert "abc"*1           == "abc"
+       #     assert "abc"*0           == ""
        fun *(i: Int): String
        do
                assert i >= 0
@@ -546,7 +773,7 @@ class String
                        current_last += my_length
                end
 
-               return new String.with_native(target_string, final_length)
+               return target_string.to_s_with_length(final_length)
        end
 
        redef fun to_s do return self
@@ -571,16 +798,92 @@ class String
        end
 end
 
+private class FlatStringReverseIterator
+       super IndexedIterator[Char]
+
+       var target: String
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: String, pos: Int)
+       do
+               target = tgt
+               target_items = tgt.items
+               curr_pos = pos + tgt.index_from
+       end
+
+       redef fun is_ok do return curr_pos >= 0
+
+       redef fun item do return target_items[curr_pos]
+
+       redef fun next do curr_pos -= 1
+
+       redef fun index do return curr_pos - target.index_from
+
+end
+
+private class FlatStringIterator
+       super IndexedIterator[Char]
+
+       var target: String
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: String, pos: Int)
+       do
+               target = tgt
+               target_items = tgt.items
+               curr_pos = pos + target.index_from
+       end
+
+       redef fun is_ok do return curr_pos <= target.index_to
+
+       redef fun item do return target_items[curr_pos]
+
+       redef fun next do curr_pos += 1
+
+       redef fun index do return curr_pos - target.index_from
+
+end
+
+private class FlatStringCharView
+       super StringCharView
+
+       redef type SELFTYPE: String
+
+       redef fun [](index)
+       do
+               # Check that the index (+ index_from) is not larger than indexTo
+               # In other terms, if the index is valid
+               assert index >= 0
+               assert (index + target._index_from) <= target._index_to
+               return target._items[index + target._index_from]
+       end
+
+       redef fun iterator_from(start) do return new FlatStringIterator.with_pos(target, start)
+
+       redef fun reverse_iterator_from(start) do return new FlatStringReverseIterator.with_pos(target, start)
+
+end
+
 # Mutable strings of characters.
 class Buffer
        super AbstractString
        super Comparable
        super StringCapable
-       super AbstractArray[Char]
 
        redef type OTHER: String
 
-       redef fun []=(index, item)
+       redef var chars: BufferCharView = new FlatBufferCharView(self)
+
+       # Modifies the char contained at pos `index`
+       #
+       # DEPRECATED : Use self.chars.[]= instead
+       fun []=(index: Int, item: Char)
        do
                if index == length then
                        add(item)
@@ -590,14 +893,21 @@ class Buffer
                _items[index] = item
        end
 
-       redef fun add(c)
+       # Adds a char `c` at the end of self
+       #
+       # DEPRECATED : Use self.chars.add instead
+       fun add(c: Char)
        do
                if _capacity <= length then enlarge(length + 5)
                _items[length] = c
                _length += 1
        end
 
-       redef fun enlarge(cap)
+       # Clears the buffer
+       fun clear do _length = 0
+
+       # Enlarges the subsequent array containing the chars of self
+       fun enlarge(cap: Int)
        do
                var c = _capacity
                if cap <= c then return
@@ -606,18 +916,7 @@ class Buffer
                _items.copy_to(a, length, 0, 0)
                _items = a
                _capacity = c
-       end
-
-       redef fun append(s)
-       do
-               if s isa String then
-                       var sl = s.length
-                       if _capacity < _length + sl then enlarge(_length + sl)
-                       s.items.copy_to(_items, sl, s._index_from, _length)
-                       _length += sl
-               else
-                       super
-               end
+               items.copy_to(a, length, 0, 0)
        end
 
        redef fun to_s: String
@@ -629,7 +928,7 @@ class Buffer
                # Ensure the afterlast byte is '\0' to nul-terminated char *
                a[length] = '\0'
 
-               return new String.with_native(a, length)
+               return a.to_s_with_length(length)
        end
 
        redef fun <(s)
@@ -638,8 +937,8 @@ class Buffer
                var l1 = length
                var l2 = s.length
                while i < l1 and i < l2 do
-                       var c1 = self[i].ascii
-                       var c2 = s[i].ascii
+                       var c1 = self.chars[i].ascii
+                       var c2 = s.chars[i].ascii
                        if c1 < c2 then
                                return true
                        else if c2 < c1 then
@@ -678,9 +977,18 @@ class Buffer
                _length = 0
        end
 
+       # Adds the content of string `s` at the end of self
+       fun append(s: String)
+       do
+               var sl = s.length
+               if capacity < length + sl then enlarge(length + sl)
+               s.items.copy_to(items, sl, s.index_from, length)
+               _length += sl
+       end
+
        redef fun ==(o)
        do
-               if not o isa Buffer or o is null then return false
+               if not o isa Buffer then return false
                var l = length
                if o.length != l then return false
                var i = 0
@@ -693,7 +1001,133 @@ class Buffer
                return true
        end
 
-       readable private var _capacity: Int 
+       readable private var _capacity: Int
+
+       # Copies the content of self in `dest`
+       fun copy(start: Int, len: Int, dest: Buffer, new_start: Int)
+       do
+               var self_chars = self.chars
+               var dest_chars = dest.chars
+               for i in [0..len-1] do
+                       dest_chars[new_start+i] = self_chars[start+i]
+               end
+       end
+
+       redef fun substring(from, count)
+       do
+               assert count >= 0
+               count += from
+               if from < 0 then from = 0
+               if count > length then count = length
+               if from < count then
+                       var r = new Buffer.with_capacity(count - from)
+                       while from < count do
+                               r.chars.push(_items[from])
+                               from += 1
+                       end
+                       return r.to_s
+               else
+                       return ""
+               end
+       end
+end
+
+private class FlatBufferReverseIterator
+       super IndexedIterator[Char]
+
+       var target: Buffer
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: Buffer, pos: Int)
+       do
+               target = tgt
+               target_items = tgt.items
+               curr_pos = pos
+       end
+
+       redef fun index do return curr_pos
+
+       redef fun is_ok do return curr_pos >= 0
+
+       redef fun item do return target_items[curr_pos]
+
+       redef fun next do curr_pos -= 1
+
+end
+
+private class FlatBufferCharView
+       super BufferCharView
+       super StringCapable
+
+       redef type SELFTYPE: Buffer
+
+       redef fun [](index) do return target._items[index]
+
+       redef fun []=(index, item)
+       do
+               assert index >= 0 and index <= length
+               if index == length then
+                       add(item)
+                       return
+               end
+               target._items[index] = item
+       end
+
+       redef fun push(c)
+       do
+               target.add(c)
+       end
+
+       redef fun add(c)
+       do
+               target.add(c)
+       end
+
+       fun enlarge(cap: Int)
+       do
+               target.enlarge(cap)
+       end
+
+       redef fun append(s)
+       do
+               var my_items = target.items
+               var s_length = s.length
+               if target.capacity < s.length then enlarge(s_length + target.length)
+       end
+
+       redef fun iterator_from(pos) do return new FlatBufferIterator.with_pos(target, pos)
+
+       redef fun reverse_iterator_from(pos) do return new FlatBufferReverseIterator.with_pos(target, pos)
+
+end
+
+private class FlatBufferIterator
+       super IndexedIterator[Char]
+
+       var target: Buffer
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: Buffer, pos: Int)
+       do
+               target = tgt
+               target_items = tgt.items
+               curr_pos = pos
+       end
+
+       redef fun index do return curr_pos
+
+       redef fun is_ok do return curr_pos < target.length
+
+       redef fun item do return target_items[curr_pos]
+
+       redef fun next do curr_pos += 1
+
 end
 
 ###############################################################################
@@ -701,19 +1135,18 @@ end
 ###############################################################################
 
 redef class Object
-       # User readable representation of `self'.
+       # User readable representation of `self`.
        fun to_s: String do return inspect
 
        # The class name of the object in NativeString format.
        private fun native_class_name: NativeString is intern
 
        # The class name of the object.
-       # FIXME: real type information is not available at runtime.
-       # Therefore, for instance, an instance of List[Bool] has just
-       # "List" for class_name
-       fun class_name: String do return new String.from_cstring(native_class_name)
+       #
+       #    assert 5.class_name == "Int"
+       fun class_name: String do return native_class_name.to_s
 
-       # Developer readable representation of `self'.
+       # Developer readable representation of `self`.
        # Usually, it uses the form "<CLASSNAME:#OBJECTID bla bla bla>"
        fun inspect: String
        do
@@ -734,44 +1167,55 @@ redef class Object
 end
 
 redef class Bool
+       #     assert true.to_s         == "true"
+       #     assert false.to_s        == "false"
        redef fun to_s
-       do 
-               if self then 
-                       return once "true" 
-               else 
-                       return once "false" 
+       do
+               if self then
+                       return once "true"
+               else
+                       return once "false"
                end
-       end   
+       end
 end
 
 redef class Int
-       fun fill_buffer(s: Buffer, base: Int, signed: Bool)
-       # Fill `s' with the digits in base 'base' of `self' (and with the '-' sign if 'signed' and negative).
+       # Fill `s` with the digits in base `base` of `self` (and with the '-' sign if 'signed' and negative).
        # assume < to_c max const of char
+       fun fill_buffer(s: Buffer, base: Int, signed: Bool)
        do
                var n: Int
                # Sign
                if self < 0 then
                        n = - self
-                       s[0] = '-'
+                       s.chars[0] = '-'
                else if self == 0 then
-                       s[0] = '0'
+                       s.chars[0] = '0'
                        return
                else
                        n = self
                end
                # Fill digits
                var pos = digit_count(base) - 1
-               while pos >= 0 and n > 0 do 
-                       s[pos] = (n % base).to_c
+               while pos >= 0 and n > 0 do
+                       s.chars[pos] = (n % base).to_c
                        n = n / base # /
                        pos -= 1
                end
        end
 
+       # C function to convert an nit Int to a NativeString (char*)
+       private fun native_int_to_s(len: Int): NativeString is extern "native_int_to_s"
+
        # return displayable int in base 10 and signed
-       redef fun to_s do return to_base(10,true)
-       
+       #
+       #     assert 1.to_s            == "1"
+       #     assert (-123).to_s       == "-123"
+       redef fun to_s do
+               var len = digit_count(10)
+               return native_int_to_s(len).to_s_with_length(len)
+       end
+
        # return displayable int in hexadecimal (unsigned (not now))
        fun to_hex: String do return to_base(16,false)
 
@@ -786,13 +1230,14 @@ redef class Int
 end
 
 redef class Float
-       # Pretty print self, print needed decimals up to a max of 6.
+       # Pretty print self, print needoed decimals up to a max of 3.
        redef fun to_s do
-               var str = to_precision( 6 )
+               var str = to_precision( 3 )
+               if is_inf != 0 or is_nan then return str
                var len = str.length
                for i in [0..len-1] do
                        var j = len-1-i
-                       var c = str[j]
+                       var c = str.chars[j]
                        if c == '0' then
                                continue
                        else if c == '.' then
@@ -804,8 +1249,40 @@ redef class Float
                return str
        end
 
-       # `self' representation with `nb' digits after the '.'.
-       fun to_precision(nb: Int): String import String::from_cstring `{
+       # `self` representation with `nb` digits after the '.'.
+       fun to_precision(nb: Int): String
+       do
+               if is_nan then return "nan"
+
+               var isinf = self.is_inf
+               if isinf == 1 then
+                       return "inf"
+               else if isinf == -1 then
+                       return  "-inf"
+               end
+
+               if nb == 0 then return self.to_i.to_s
+               var f = self
+               for i in [0..nb[ do f = f * 10.0
+               if self > 0.0 then
+                       f = f + 0.5
+               else
+                       f = f - 0.5
+               end
+               var i = f.to_i
+               if i == 0 then return "0.0"
+               var s = i.to_s
+               var sl = s.length
+               if sl > nb then
+                       var p1 = s.substring(0, s.length-nb)
+                       var p2 = s.substring(s.length-nb, nb)
+                       return p1 + "." + p2
+               else
+                       return "0." + ("0"*(nb-sl)) + s
+               end
+       end
+
+       fun to_precision_native(nb: Int): String import NativeString.to_s `{
                int size;
                char *str;
 
@@ -813,15 +1290,16 @@ redef class Float
                str = malloc(size + 1);
                sprintf(str, "%.*f", (int)nb, recv );
 
-               return new_String_from_cstring( str );
+               return NativeString_to_s( str );
        `}
 end
 
 redef class Char
+       #     assert 'x'.to_s    == "x"
        redef fun to_s
        do
                var s = new Buffer.with_capacity(1)
-               s[0] = self
+               s.chars[0] = self
                return s.to_s
        end
 
@@ -859,18 +1337,21 @@ redef class Collection[E]
                return s.to_s
        end
 
-       # Concatenate and separate each elements with `sep'. 
+       # Concatenate and separate each elements with `sep`.
+       #
+       #     assert [1, 2, 3].join(":")         == "1:2:3"
+       #     assert [1..3].join(":")            == "1:2:3"
        fun join(sep: String): String
        do
                if is_empty then return ""
-               
+
                var s = new Buffer # Result
 
                # Concat first item
                var i = iterator
                var e = i.item
                if e != null then s.append(e.to_s)
-               
+
                # Concat other items
                i.next
                while i.is_ok do
@@ -901,27 +1382,32 @@ end
 
 redef class Map[K,V]
        # Concatenate couple of 'key value'.
-       # key and value are separated by 'couple_sep'.
-       # each couple is separated each couple with `sep'.
+       # key and value are separated by `couple_sep`.
+       # each couple is separated each couple with `sep`.
+       #
+       #     var m = new ArrayMap[Int, String]
+       #     m[1] = "one"
+       #     m[10] = "ten"
+       #     assert m.join("; ", "=") == "1=one; 10=ten"
        fun join(sep: String, couple_sep: String): String
        do
                if is_empty then return ""
-               
+
                var s = new Buffer # Result
 
                # Concat first item
                var i = iterator
                var k = i.key
                var e = i.item
-               if e != null then s.append("{k}{couple_sep}{e}")
-               
+               s.append("{k}{couple_sep}{e or else "<null>"}")
+
                # Concat other items
                i.next
                while i.is_ok do
                        s.append(sep)
                        k = i.key
                        e = i.item
-                       if e != null then s.append("{k}{couple_sep}{e}")
+                       s.append("{k}{couple_sep}{e or else "<null>"}")
                        i.next
                end
                return s.to_s
@@ -934,10 +1420,12 @@ end
 
 # Native strings are simple C char *
 class NativeString
+       super StringCapable
+
        fun [](index: Int): Char is intern
        fun []=(index: Int, item: Char) is intern
        fun copy_to(dest: NativeString, length: Int, from: Int, to: Int) is intern
-       
+
        # Position of the first nul character.
        fun cstring_length: Int
        do
@@ -947,6 +1435,26 @@ class NativeString
        end
        fun atoi: Int is intern
        fun atof: Float is extern "atof"
+
+       redef fun to_s
+       do
+               return to_s_with_length(cstring_length)
+       end
+
+       fun to_s_with_length(length: Int): String
+       do
+               assert length >= 0
+               return new String.with_infos(self, length, 0, length - 1)
+       end
+
+       fun to_s_with_copy: String
+       do
+               var length = cstring_length
+               var new_self = calloc_string(length + 1)
+               copy_to(new_self, length, 0, 0)
+               return new String.with_infos(new_self, length, 0, length - 1)
+       end
+
 end
 
 # StringCapable objects can create native strings
@@ -966,24 +1474,26 @@ redef class Sys
        # The name of the program as given by the OS
        fun program_name: String
        do
-               return new String.from_cstring(native_argv(0))
+               return native_argv(0).to_s
        end
 
-       # Initialize `args' with the contents of `native_argc' and `native_argv'.
+       # Initialize `args` with the contents of `native_argc` and `native_argv`.
        private fun init_args
        do
                var argc = native_argc
                var args = new Array[String].with_capacity(0)
                var i = 1
                while i < argc do
-                       args[i-1] = new String.from_cstring(native_argv(i))
+                       args[i-1] = native_argv(i).to_s
                        i += 1
                end
                _args_cache = args
        end
 
-       private fun native_argc: Int is extern "kernel_Sys_Sys_native_argc_0" # First argument of the main C function.
-       
-       private fun native_argv(i: Int): NativeString is extern "kernel_Sys_Sys_native_argv_1" # Second argument of the main C function.
+       # First argument of the main C function.
+       private fun native_argc: Int is intern
+
+       # Second argument of the main C function.
+       private fun native_argv(i: Int): NativeString is intern
 end