convert rollfoward to function

schema/functions/rollforward.sql

@@ -1,22 +1,18 @@
+CREATE FUNCTION evt.balrf(_mind tstzrange, _maxd tstzrange) RETURNS void AS
+$func$
+BEGIN
     WITH
---min and max periods
-minmax AS (
-    SELECT
-    (SELECT lower(dur) FROM evt.fspr WHERE id = '2018.08') mind
-    ,(SELECT lower(dur) FROM evt.fspr WHERE id = '2018.11') maxd
-)
     --list each period in min and max
-,prng AS (
+    prng AS (
         SELECT 
             id
             ,dur
             ,prop
         FROM
             evt.fspr f
-        CROSS JOIN minmax
         WHERE
-        lower(f.dur) >= mind
-        AND lower(f.dur) <= maxd
+            f.dur >= _mind
+            AND f.dur <= _maxd
     )
     --get every account involved in target range
     ,arng AS (
@@ -85,4 +81,7 @@ ON CONFLICT ON CONSTRAINT bal_pk DO UPDATE SET
         obal = EXCLUDED.obal
         ,debits = EXCLUDED.debits
         ,credits = EXCLUDED.credits
-    ,cbal = EXCLUDED.cbal
+        ,cbal = EXCLUDED.cbal;
+END;
+$func$
+LANGUAGE plpgsql