Add period-based exchange rates.

Makefile

@@ -253,7 +253,8 @@ bank-fio.o: bank-fio.import.scm
 bank-fio.import.scm: $(BANK-FIO-SOURCES)
 
 MEMBERS-PAYMENTS-SOURCES=members-payments.scm bank-account.import.scm	\
-	dictionary.import.scm member-fees.import.scm
+	dictionary.import.scm member-fees.import.scm			\
+	period.import.scm
 
 members-payments.so: members-payments.o
 members-payments.o: members-payments.import.scm

members-payments.scm

@@ -41,9 +41,18 @@
 	 member-record
 	 members-base
 	 bank-fio
-
 	 dictionary
-	 member-fees)
+	 member-fees
+	 period)
+
+ ;; Exchange rates
+ (define exchange-rates-lookup-table
+   (make-period-lookup-table
+    '(((2010 1) 25))))
+
+ ;; Lookup CZK/EUR
+ (define (lookup-eur-rate)
+   (car (lookup-by-period exchange-rates-lookup-table)))
 
  ;; Extract probable member-id from transaction
  (define (transaction-extract-member-id transaction)