1 files changed, 48 insertions, 0 deletions
diff --git a/challenge-099/abigail/lua/ch-2.lua b/challenge-099/abigail/lua/ch-2.lua
new file mode 100644
index 0000000000..f1a8ad5253
--- /dev/null
+++ b/challenge-099/abigail/lua/ch-2.lua
@@ -0,0 +1,48 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-2.lua < input-file
+--
+
+-- 
+-- Recursively count matches:
+--   - If either the string or the pattern is empty, there are no matches.
+--   - Else, + count the matches if we don't match at the first character
+--             if the string.
+--           + if the first character of the string equals the first
+--             character of the pattern:
+--             o  add 1 if the pattern is just one character long
+--             o  else, add the number of matches starting from the
+--                then next character in the string, and the next
+--                character in the pattern.
+--
+function matches (str, pattern)
+    if  str : len () == 0  or  pattern : len () == 0  then
+        return 0
+    end
+
+    local count = matches (str : sub (2), pattern)
+    if  str : sub (1, 1) == pattern : sub (1, 1) then
+        if  pattern : len () == 1 then
+            count = count + 1
+        else 
+            count = count + matches (str : sub (2), pattern : sub (2))
+        end
+    end
+    return (count)
+end
+
+
+--
+-- Read input from standard input, assuming one exercise per line.
+-- Each line consists of a string $S, and a pattern $T, separated
+-- by whitespace.
+--
+for line in io . lines () do
+    local str, pattern = line : match ("(%S+) +(%S+)")
+    print (matches (str, pattern))
+end