stdlib/strings: Moved Buffer to FlatBuffer, Buffer is now abstract.
[nit.git] / lib / standard / string.nit
index 34bf210..e4c9fe4 100644 (file)
@@ -5,17 +5,17 @@
 #
 # 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>
@@ -25,50 +25,127 @@ import hash
 # 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
 
-       # Access a character at `index` in the string.
-       #
-       #     assert "abcd"[2]         == 'c'
-       redef fun [](index) do return _items[index]
+       # Number of characters contained in self.
+       fun length: Int is abstract
 
        # Create a substring.
        #
-       #     assert "abcd".substring(1, 2)         ==  "bc"
-       #     assert "abcd".substring(-1, )         ==  "a"
-       #     assert "abcd".substring(1, 0)         ==  ""
-       #     assert "abcd".substring(2, 5)         ==  "cd"
+       #     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
+       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
 
+       # Gets an iterator on the chars of self
+       #
+       # 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"
+       #     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
@@ -83,25 +160,22 @@ abstract class AbstractString
        #     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`?
        #
-       #     assert "abcd".has_prefix("ab")         ==  true
-       #     assert "abcbc".has_prefix("bc")        ==  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`?
@@ -124,7 +198,7 @@ abstract class AbstractString
        #
        #     assert "123".to_f        == 123.0
        #     assert "-1".to_f         == -1.0
-       #     assert "-1.2e-3".to_f    == -1.2e-3
+       #     assert "-1.2e-3".to_f    == -0.0012
        fun to_f: Float
        do
                # Shortcut
@@ -142,7 +216,7 @@ abstract class AbstractString
                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
@@ -173,7 +247,7 @@ abstract class AbstractString
        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
@@ -193,8 +267,8 @@ abstract class AbstractString
        #     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)
+               var s = new FlatBuffer.with_capacity(length)
+               for i in self.chars do s.add(i.to_upper)
                return s.to_s
        end
 
@@ -203,8 +277,8 @@ abstract class AbstractString
        #     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)
+               var s = new FlatBuffer.with_capacity(length)
+               for i in self.chars do s.add(i.to_lower)
                return s.to_s
        end
 
@@ -215,32 +289,236 @@ abstract class AbstractString
        #     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 FlatBuffer
+               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 FlatBuffer
+               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 FlatBuffer
+               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 FlatBuffer.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
+
+       private var items: NativeString
+
+       redef var length: Int
+
+       init do end
+
        redef fun output
        do
                var i = 0
                while i < length do
-                       _items[i].output
+                       items[i].output
                        i += 1
                end
        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
@@ -250,10 +528,12 @@ class String
        redef type OTHER: String
 
        # Index in _items of the start of the string
-       readable var _index_from: Int
+       private var index_from: Int
 
        # Indes in _items of the last item of the string
-       readable var _index_to: Int
+       private var index_to: Int
+
+       redef var chars: StringCharView = new FlatStringCharView(self)
 
        ################################################
        #       AbstractString specific methods        #
@@ -263,8 +543,8 @@ class String
                assert index >= 0
                # Check that the index (+ index_from) is not larger than indexTo
                # In other terms, if the index is valid
-               assert (index + _index_from) <= _index_to
-               return _items[index + _index_from]
+               assert (index + index_from) <= index_to
+               return items[index + index_from]
        end
 
        redef fun substring(from: Int, count: Int): String
@@ -277,54 +557,25 @@ class String
                        from = 0
                end
 
-               var realFrom = _index_from + from
+               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
 
-       redef fun substring_from(from: Int): String
-       do
-               if from > _length then return ""
-               if from < 0 then from = 0
-               return substring(from, _length)
-       end
-
-       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
+               return new String.with_infos(items, to - realFrom + 1, realFrom, to)
        end
 
        redef fun to_upper: String
        do
-               var outstr = calloc_string(self._length + 1)
+               var outstr = calloc_string(self.length + 1)
                var out_index = 0
 
-               var myitems = self._items
-               var index_from = self._index_from
-               var max = self._index_to
+               var myitems = self.items
+               var index_from = self.index_from
+               var max = self.index_to
 
                while index_from <= max do
                        outstr[out_index] = myitems[index_from].to_upper
@@ -334,17 +585,17 @@ class String
 
                outstr[self.length] = '\0'
 
-               return outstr.to_s_with_length(self._length)
+               return outstr.to_s_with_length(self.length)
        end
 
        redef fun to_lower : String
        do
-               var outstr = calloc_string(self._length + 1)
+               var outstr = calloc_string(self.length + 1)
                var out_index = 0
 
-               var myitems = self._items
-               var index_from = self._index_from
-               var max = self._index_to
+               var myitems = self.items
+               var index_from = self.index_from
+               var max = self.index_to
 
                while index_from <= max do
                        outstr[out_index] = myitems[index_from].to_lower
@@ -354,23 +605,23 @@ class String
 
                outstr[self.length] = '\0'
 
-               return outstr.to_s_with_length(self._length)
+               return outstr.to_s_with_length(self.length)
        end
 
        redef fun trim: String
        do
-               if self._length == 0 then return self
+               if self.length == 0 then return self
                # find position of the first non white space char (ascii < 32) from the start of the string
-               var start_pos = self._index_from
-               while _items[start_pos].ascii <= 32 do
+               var start_pos = self.index_from
+               while items[start_pos].ascii <= 32 do
                        start_pos += 1
-                       if start_pos == _index_to + 1 then return ""
+                       if start_pos == index_to + 1 then return ""
                end
                # find position of the first non white space char from the end of the string
-               var end_pos = _index_to
-               while _items[end_pos].ascii <= 32 do
+               var end_pos = index_to
+               while items[end_pos].ascii <= 32 do
                        end_pos -= 1
-                       if end_pos == start_pos then return _items[start_pos].to_s
+                       if end_pos == start_pos then return items[start_pos].to_s
                end
                start_pos -= index_from
                end_pos -= index_from
@@ -379,10 +630,10 @@ class String
 
        redef fun output
        do
-               var i = self._index_from
-               var imax = self._index_to
+               var i = self.index_from
+               var imax = self.index_to
                while i <= imax do
-                       _items[i].output
+                       items[i].output
                        i += 1
                end
        end
@@ -391,57 +642,43 @@ 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)
-       do
-               _items = internalString
-               _index_from = from
-               _index_to = to
-               _length = to - from + 1
-       end
-
        private init with_infos(items: NativeString, len: Int, from: Int, to: Int)
        do
-               self._items = items
-               _length = len
-               _index_from = from
-               _index_to = to
+               self.items = items
+               length = len
+               index_from = from
+               index_to = to
        end
 
        # Return a null terminated char *
        fun to_cstring: NativeString
        do
-               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)
+               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)
                        newItems[length] = '\0'
                        return newItems
                end
-               return _items
+               return items
        end
 
        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
 
-               var my_length = _length
+               var my_length = length
 
-               if other._length != my_length then return false
+               if other.length != my_length then return false
 
-               var my_index = _index_from
-               var its_index = other._index_from
+               var my_index = index_from
+               var its_index = other.index_from
 
                var last_iteration = my_index + my_length
 
-               var itsitems = other._items
-               var myitems = self._items
+               var itsitems = other.items
+               var myitems = self.items
 
                while my_index < last_iteration do
                        if myitems[my_index] != itsitems[its_index] then return false
@@ -454,7 +691,7 @@ class String
 
        # The comparison between two strings is done on a lexicographical basis
        #
-       #     assert "aa" < "b"      ==  true
+       #     assert ("aa" < "b")      ==  true
        redef fun <(other)
        do
                if self.object_id == other.object_id then return false
@@ -462,14 +699,14 @@ class String
                var my_curr_char : Char
                var its_curr_char : Char
 
-               var curr_id_self = self._index_from
-               var curr_id_other = other._index_from
+               var curr_id_self = self.index_from
+               var curr_id_other = other.index_from
 
-               var my_items = self._items
-               var its_items = other._items
+               var my_items = self.items
+               var its_items = other.items
 
-               var my_length = self._length
-               var its_length = other._length
+               var my_length = self.length
+               var its_length = other.length
 
                var max_iterations = curr_id_self + my_length
 
@@ -494,15 +731,15 @@ class String
        #     assert "hello " + "world!"         == "hello world!"
        fun +(s: String): String
        do
-               var my_length = self._length
-               var its_length = s._length
+               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)
+               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[total_length] = '\0'
 
@@ -518,11 +755,11 @@ class String
        do
                assert i >= 0
 
-               var my_length = self._length
+               var my_length = self.length
 
                var final_length = my_length * i
 
-               var my_items = self._items
+               var my_items = self.items
 
                var target_string = calloc_string((final_length) + 1)
 
@@ -544,15 +781,15 @@ class String
        do
                # djb2 hash algorythm
                var h = 5381
-               var i = _length - 1
+               var i = length - 1
 
-               var myitems = _items
-               var strStart = _index_from
+               var myitems = items
+               var strStart = index_from
 
                i += strStart
 
                while i >= strStart do
-                       h = (h * 32) + h + self._items[i].ascii
+                       h = (h * 32) + h + self.items[i].ascii
                        i -= 1
                end
 
@@ -560,15 +797,116 @@ 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
+
+abstract class Buffer
+       super Text
+
+       # Modifies the char contained at pos `index`
+       #
+       # DEPRECATED : Use self.chars.[]= instead
+       fun []=(index: Int, item: Char) is abstract
+
+       # Adds a char `c` at the end of self
+       #
+       # DEPRECATED : Use self.chars.add instead
+       fun add(c: Char) is abstract
+
+       # Clears the buffer
+       fun clear is abstract
+
+       # Enlarges the subsequent array containing the chars of self
+       fun enlarge(cap: Int) is abstract
+
+       # Adds the content of string `s` at the end of self
+       fun append(s: String) is abstract
+
+       redef fun chars: BufferCharView is abstract
+end
+
 # Mutable strings of characters.
-class Buffer
+class FlatBuffer
        super AbstractString
        super Comparable
        super StringCapable
-       super AbstractArray[Char]
+       super Buffer
 
        redef type OTHER: String
 
+       redef var chars: FlatBufferCharView = new FlatBufferCharView(self)
+
+       var capacity: Int
+
        redef fun []=(index, item)
        do
                if index == length then
@@ -576,44 +914,35 @@ class Buffer
                        return
                end
                assert index >= 0 and index < length
-               _items[index] = item
+               items[index] = item
        end
 
        redef fun add(c)
        do
-               if _capacity <= length then enlarge(length + 5)
-               _items[length] = c
-               _length += 1
+               if capacity <= length then enlarge(length + 5)
+               items[length] = c
+               length += 1
        end
 
+       redef fun clear do length = 0
+
        redef fun enlarge(cap)
        do
-               var c = _capacity
+               var c = capacity
                if cap <= c then return
                while c <= cap do c = c * 2 + 2
                var a = calloc_string(c+1)
-               _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)
+               items = a
+               capacity = c
+               items.copy_to(a, length, 0, 0)
        end
 
        redef fun to_s: String
        do
                var l = length
                var a = calloc_string(l+1)
-               _items.copy_to(a, l, 0, 0)
+               items.copy_to(a, l, 0, 0)
 
                # Ensure the afterlast byte is '\0' to nul-terminated char *
                a[length] = '\0'
@@ -627,8 +956,8 @@ 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
@@ -651,10 +980,10 @@ class Buffer
 
        init from(s: String)
        do
-               _capacity = s.length + 1
-               _length = s.length
-               _items = calloc_string(_capacity)
-               s.items.copy_to(_items, _length, s._index_from, 0)
+               capacity = s.length + 1
+               length = s.length
+               items = calloc_string(capacity)
+               s.items.copy_to(items, length, s.index_from, 0)
        end
 
        # Create a new empty string with a given capacity.
@@ -662,19 +991,27 @@ class Buffer
        do
                assert cap >= 0
                # _items = new NativeString.calloc(cap)
-               _items = calloc_string(cap+1)
-               _capacity = cap
-               _length = 0
+               items = calloc_string(cap+1)
+               capacity = cap
+               length = 0
+       end
+
+       redef fun append(s)
+       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 FlatBuffer then return false
                var l = length
                if o.length != l then return false
                var i = 0
-               var it = _items
-               var oit = o._items
+               var it = items
+               var oit = o.items
                while i < l do
                        if it[i] != oit[i] then return false
                        i += 1
@@ -682,7 +1019,131 @@ class Buffer
                return true
        end
 
-       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 FlatBuffer.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: FlatBuffer
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: FlatBuffer, 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: FlatBuffer
+
+       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: FlatBuffer
+
+       var target_items: NativeString
+
+       var curr_pos: Int
+
+       init with_pos(tgt: FlatBuffer, 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
 
 ###############################################################################
@@ -725,13 +1186,13 @@ 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
@@ -743,17 +1204,17 @@ redef class 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
@@ -778,7 +1239,7 @@ redef class Int
        fun to_base(base: Int, signed: Bool): String
        do
                var l = digit_count(base)
-               var s = new Buffer.from(" " * l)
+               var s = new FlatBuffer.from(" " * l)
                fill_buffer(s, base, signed)
                return s.to_s
        end
@@ -788,10 +1249,11 @@ redef class Float
        # Pretty print self, print needoed decimals up to a max of 3.
        redef fun to_s do
                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
@@ -806,6 +1268,15 @@ redef class Float
        # `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
@@ -827,7 +1298,7 @@ redef class Float
                end
        end
 
-       fun to_precision_native(nb: Int): String import NativeString::to_s `{
+       fun to_precision_native(nb: Int): String import NativeString.to_s `{
                int size;
                char *str;
 
@@ -843,8 +1314,8 @@ redef class Char
        #     assert 'x'.to_s    == "x"
        redef fun to_s
        do
-               var s = new Buffer.with_capacity(1)
-               s[0] = self
+               var s = new FlatBuffer.with_capacity(1)
+               s.chars[0] = self
                return s.to_s
        end
 
@@ -877,7 +1348,7 @@ redef class Collection[E]
        # Concatenate elements.
        redef fun to_s
        do
-               var s = new Buffer
+               var s = new FlatBuffer
                for e in self do if e != null then s.append(e.to_s)
                return s.to_s
        end
@@ -889,14 +1360,14 @@ redef class Collection[E]
        fun join(sep: String): String
        do
                if is_empty then return ""
-               
-               var s = new Buffer # Result
+
+               var s = new FlatBuffer # 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
@@ -913,7 +1384,7 @@ redef class Array[E]
        # Fast implementation
        redef fun to_s
        do
-               var s = new Buffer
+               var s = new FlatBuffer
                var i = 0
                var l = length
                while i < l do
@@ -937,22 +1408,22 @@ redef class Map[K,V]
        fun join(sep: String, couple_sep: String): String
        do
                if is_empty then return ""
-               
-               var s = new Buffer # Result
+
+               var s = new FlatBuffer # 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