lib/counter: introduce Counter::dec

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --git a/lib/counter.nit b/lib/counter.nit
index 6545b73..6d5729d 100644 (file)
--- a/lib/counter.nit
+++ b/lib/counter.nit
@@ -93,6 +93,22 @@ class Counter[E]
                for e in es do inc(e)
        end
 
+       # Decrement the value of `e` by 1
+       fun dec(e: E) do
+               if not has_key(e) then
+                       self.map[e] = 0
+               else
+                       self.map[e] = self[e] - 1
+                       sum += - 1
+               end
+       end
+
+       # Decrement the value for each element of `es`
+       fun dec_all(es: Collection[E])
+       do
+               for e in es do dec(e)
+       end
+
        # A new Counter initialized with `inc_all`.
        init from(es: Collection[E])
        do