--- a/progs/matcher/re3.sc	Mon Jan 24 00:14:02 2022 +0000
+++ b/progs/matcher/re3.sc	Tue Mar 22 00:36:18 2022 +0000
@@ -187,3 +187,43 @@
 
 
 // runs with amm2 and amm3
+
+def pp(r: Rexp): String = r match {
+  case SEQ(CHAR(a1), SEQ(r1, r2)) => s"${a1}${pp(r1)}${pp(r2)}"
+  case SEQ(ONE, SEQ(r1, r2)) => s"1${pp(r1)}${pp(r2)}"
+  case SEQ(ZERO, SEQ(r1, r2)) => s"0${pp(r1)}${pp(r2)}"
+  case SEQ(CHAR(a1), CHAR(a2)) => s"${a1}${a2}"
+  case SEQ(ONE, CHAR(a2)) => s"1${a2}"
+  case SEQ(ZERO, CHAR(a2)) => s"0${a2}" 
+  case ZERO => "0"
+  case ONE => "1"
+  case CHAR(a) => a.toString
+  case ALT(r1, r2) => s"(${pp(r1)} + ${pp(r2)})"
+  case SEQ(r1, r2) => s"(${pp(r1)} o ${pp(r2)})"
+  case STAR(r1) => s"(${pp(r1)})*"
+}
+
+
+val REG = STAR(ALT(CHAR('a'), SEQ(CHAR('a'), CHAR('a'))))
+
+print(pp(ders("".toList, REG)))
+print(pp(ders("a".toList, REG)))
+print(pp(ders("aa".toList, REG)))
+print(pp(ders("aaa".toList, REG)))
+
+size(ders("".toList, REG))        // 6
+size(ders("a".toList, REG))       // 12
+size(ders("aa".toList, REG))      // 27
+size(ders("aaa".toList, REG))     // 55
+size(ders("aaaa".toList, REG))    // 8
+size(ders("aaaaa".toList, REG))   // 169
+size(ders("aaaaaa".toList, REG))  // 283
+size(ders(("a" * 7).toList, REG)) // 468
+size(ders(("a" * 8).toList, REG)) // 767
+size(ders(("a" * 9).toList, REG)) // 1251
+size(ders(("a" * 10).toList, REG))// 2034
+size(ders(("a" * 11).toList, REG))// 3301
+
+for (i <- (0 to 40)) {
+  println(s"$i:" + size(ders(("a" * i).toList, REG)))
+}
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