jonsecchis · December 24, 2021 19:18 · Dec 24, 2021
diff --git a/spec.log b/spec.log
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+Ledger
+  Entries is sequence of Position and Operation
+
+Position
+  Shares is Number
+  Average Share Cost is Number
+  Gains is (Gross Gain, Net Gain) is (Number, Number)
+  Tax is Number
+  Total is Shares times Average Share Cost
+
+Operation
+  is Buy or Sell
+  Shares is Number
+  Share Cost is Number
+  Total is Shares times Share Cost
+
+Operations is sequence of Operation
+
+Ledger for Operations and Position
+  Entries is sequence of, Position is (last Position or Position) after Operation
+                          Operation is Operation
+
+Shares of Position after Operation
+  is, if Operation is Buy
+         then (Position Shares plus Operation Shares)
+      if Operation is Sell
+         then (Position Shares minus Operation Shares)
+
+Average Share Cost of Position after Operation
+  is, if Operation is Buy
+         then (Position Total plus Operation Total) divided by (Position Shares plus Operation Shares)
+      if Operation is Sell
+         then (Position Average Share Cost)
+
+Gains of Position after Operation
+  Gross Gain is, if Operation is Buy
+                    then Zero
+                 if Operation is Sell
+                    then (Operation Share Cost minus Position Average Share Cost) times Operation Shares
+  Net Gain is Position Net Gain plus Gross Gain
+
+Tax of Position after Operation and Gains
+  is, if Operation is Sell
+      and Operation Total is greater than some TAXATION THRESHOLD
+      and Gross Gains is greater than Zero
+      and Net Gains is greater than Zero
+          then (Net Gains times some TAXATION FACTOR)
+      else Zero
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