Use the same algorithm for expected income in summary emails.

src/members-fees.scm

@@ -41,12 +41,14 @@
   member-calendar->table
   members-summary
   member-calendar-entry->fee
+  get-expected-income-string
   )
 
  (import scheme
 	 (chicken base)
 	 (chicken format)
 	 (chicken sort)
+	 (chicken string)
 	 srfi-1
 	 configuration
 	 brmember
@@ -205,5 +207,26 @@
 		    (+ (cdr acc) (if (brmember-student? mr) 0 1))))
 	    (cons 0 0)
 	    members)))
+
+ (define (get-expected-income-string mb)
+   (let* ((flst
+	   (map (compose member-calendar-entry->fee make-member-calendar-entry)
+		(find-members-by-predicate mb brmember-active?)))
+	  (amts (sort (delete-duplicates flst) <))
+	  (sums
+	   (map
+	    (lambda (amt)
+	      (cons amt
+		    (length (filter (lambda (v) (= v amt)) flst))))
+	    amts)))
+     (string-append
+      "Expected income: "
+      (string-intersperse (map
+			   (lambda (p)
+			     (format "~A*~A" (cdr p) (car p)))
+			   sums)
+			  " + ")
+      " = "
+      (number->string (foldl + 0 (map (lambda (p) (* (car p) (cdr p))) sums))))))
  
  )