Rename Pattern to Regex.

toRegex now converts string to our regex, and toPattern converts to JVM Pattern.

libraries/stdlib/test/text/RegexTest.kt

@@ -0,0 +1,74 @@
+package test.text
+
+import kotlin.text.*
+
+import kotlin.test.*
+import org.junit.Test as test
+
+class RegexTest {
+
+    test fun matchResult() {
+        val p = "\\d+".toRegex()
+        val input = "123 456 789"
+
+        val first = p.match(input)
+        assertTrue(first != null); first!!
+        assertEquals("123", first.value)
+
+        val second1 = first.next()!!
+        val second2 = first.next()!!
+
+        assertEquals("456", second1.value)
+        assertEquals(second1.value, second2.value)
+
+        val last = second1.next()!!
+        assertEquals("789", last.value)
+
+        val noMatch = last.next()
+        assertEquals(null, noMatch)
+    }
+
+    test fun matchSequence() {
+        val input = "123 456 789"
+        val pattern = "\\d+".toRegex()
+
+        val matches = pattern.matchAll(input)
+        val values = matches.map { it.value }
+        val expected = listOf("123", "456", "789")
+        assertEquals(expected, values.toList())
+        assertEquals(expected, values.toList(), "running match sequence second time")
+
+        assertEquals(listOf(0..2, 4..6, 8..10), matches.map { it.range }.toList())
+    }
+
+    test fun matchGroups() {
+        val input = "1a 2b 3c"
+        val pattern = "(\\d)(\\w)".toRegex()
+
+        val matches = pattern.matchAll(input).toList()
+        assertTrue(matches.all { it.groups.size() == 3 })
+        val m1 = matches[0]
+        assertEquals("1a", m1.groups[0]?.value)
+        assertEquals("1", m1.groups[1]?.value)
+        assertEquals("a", m1.groups[2]?.value)
+
+        val m2 = matches[1]
+        assertEquals("2", m2.groups[1]?.value)
+        assertEquals("b", m2.groups[2]?.value)
+    }
+
+    test fun matchOptionalGroup() {
+        val pattern = "(hi)|(bye)".toRegex(RegexOption.IGNORE_CASE)
+
+        val m1 = pattern.match("Hi!")!!
+        assertEquals(3, m1.groups.size())
+        assertEquals("Hi", m1.groups[1]?.value)
+        assertEquals(null, m1.groups[2])
+
+        val m2 = pattern.match("bye...")!!
+        assertEquals(3, m2.groups.size())
+        assertEquals(null, m2.groups[1])
+        assertEquals("bye", m2.groups[2]?.value)
+    }
+
+}