X-Git-Url: http://nitlanguage.org

diff --git a/lib/core/text/abstract_text.nit b/lib/core/text/abstract_text.nit
index 32628cd..fc8ec5b 100644
--- a/lib/core/text/abstract_text.nit
+++ b/lib/core/text/abstract_text.nit
@@ -248,7 +248,17 @@ abstract class Text
 	# If `self` contains only digits and alpha <= 'f', return the corresponding integer.
 	#
 	#     assert "ff".to_hex == 255
-	fun to_hex: Int do return a_to(16)
+	fun to_hex(pos, ln: nullable Int): Int do
+		var res = 0
+		if pos == null then pos = 0
+		if ln == null then ln = length - pos
+		var max = pos + ln
+		for i in [pos .. max[ do
+			res <<= 4
+			res += self[i].from_hex
+		end
+		return res
+	end
 
 	# If `self` contains only digits <= '7', return the corresponding integer.
 	#
@@ -733,21 +743,32 @@ abstract class Text
 	#     assert "\\ud800\\udfd3".from_utf16_escape == '𐏓'
 	#     assert "\\u00e8".from_utf16_escape == 'è'
 	#     assert "\\u3042".from_utf16_escape == 'あ'
-	fun from_utf16_escape: Char do
-		var ln = length
-		if ln != 6 and ln != 12 then return 0xFFFD.code_point
-		var cphi = substring(2, 4).to_hex
-		if cphi < 0xD800 then return cphi.code_point
-		if cphi > 0xDFFF then return cphi.code_point
-		if cphi > 0xDBFF then return 0xFFFD.code_point
-		var cp = 0
-		cp += (cphi - 0xD800) << 10
-		var cplo = substring(8, 4).to_hex
+	fun from_utf16_escape(pos, ln: nullable Int): Char do
+		if pos == null then pos = 0
+		if ln == null then ln = length - pos
+		if ln < 6 then return 0xFFFD.code_point
+		var cp = from_utf16_digit(pos + 2)
+		if cp < 0xD800 then return cp.code_point
+		if cp > 0xDFFF then return cp.code_point
+		if cp > 0xDBFF then return 0xFFFD.code_point
+		if ln == 6 then return 0xFFFD.code_point
+		if ln < 12 then return 0xFFFD.code_point
+		cp <<= 16
+		cp += from_utf16_digit(pos + 8)
+		var cplo = cp & 0xFFFF
 		if cplo < 0xDC00 then return 0xFFFD.code_point
 		if cplo > 0xDFFF then return 0xFFFD.code_point
-		cp += cplo - 0xDC00
-		cp += 0x10000
-		return cp.code_point
+		return cp.from_utf16_surr.code_point
+	end
+
+	# Returns a UTF-16 escape value
+	#
+	#     var s = "\\ud800\\udfd3"
+	#     assert s.from_utf16_digit(2) == 0xD800
+	#     assert s.from_utf16_digit(8) == 0xDFD3
+	fun from_utf16_digit(pos: nullable Int): Int do
+		if pos == null then pos = 0
+		return to_hex(pos, 4)
 	end
 
 	# Encode `self` to percent (or URL) encoding
@@ -974,6 +995,65 @@ abstract class Text
 		return s.plain_to_s
 	end
 
+	# Return the Levenshtein distance between two strings
+	#
+	# ~~~
+	# assert "abcd".levenshtein_distance("abcd") == 0
+	# assert "".levenshtein_distance("abcd")     == 4
+	# assert "abcd".levenshtein_distance("")     == 4
+	# assert "abcd".levenshtein_distance("xyz")  == 4
+	# assert "abcd".levenshtein_distance("xbdy") == 3
+	# ~~~
+	fun levenshtein_distance(other: String): Int
+	do
+		var slen = self.length
+		var olen = other.length
+
+		# fast cases
+		if slen == 0 then return olen
+		if olen == 0 then return slen
+		if self == other then return 0
+
+		# previous row of distances
+		var v0 = new Array[Int].with_capacity(olen+1)
+
+		# current row of distances
+		var v1 = new Array[Int].with_capacity(olen+1)
+
+		for j in [0..olen] do
+			# prefix insert cost
+			v0[j] = j
+		end
+
+		for i in [0..slen[ do
+
+			# prefix delete cost
+			v1[0] = i + 1
+
+			for j in [0..olen[ do
+				# delete cost
+				var cost1 = v1[j] + 1
+				# insert cost
+				var cost2 = v0[j + 1] + 1
+				# same char cost (+0)
+				var cost3 = v0[j]
+				# change cost
+				if self[i] != other[j] then cost3 += 1
+				# keep the min
+				v1[j+1] = cost1.min(cost2).min(cost3)
+			end
+
+			# Switch columns:
+			# * v1 become v0 in the next iteration
+			# * old v0 is reused as the new v1
+			var tmp = v1
+			v1 = v0
+			v0 = tmp
+		end
+
+		return v0[olen]
+	end
+
 	# Copies `n` bytes from `self` at `src_offset` into `dest` starting at `dest_offset`
 	#
 	# Basically a high-level synonym of NativeString::copy_to
@@ -1600,6 +1680,12 @@ redef class Char
 	#     assert 'ま'.bytes == [0xE3u8, 0x81u8, 0xBEu8]
 	fun bytes: SequenceRead[Byte] do return to_s.bytes
 
+	# Is `self` an UTF-16 surrogate pair ?
+	fun is_surrogate: Bool do
+		var cp = code_point
+		return cp >= 0xD800 and cp <= 0xDFFF
+	end
+
 	# Length of `self` in a UTF-8 String
 	private fun u8char_len: Int do
 		var c = self.code_point