complete type annotations

parking.scm

@@ -1,13 +1,21 @@
 ;;;; A program to print out the current real-time status of the computer parking terminal equipped
 ;;;; parking garages in the city of Linköping using the municipal open data API.
 
-(import medea)
 (import http-client)
 (import srfi-1)
 (import (chicken io))
 (import srfi-13)
 (import srfi-14)
 (import (chicken condition))
+(import medea)
+
+;; We want members to be parsed as lowercase symbols, and arrays to be parsed as lists.
+;; This is not a legal way to parse json, which requires case-sensitive members
+;; but makes for neater scheme code.
+(json-parsers (append `((member . ,(lambda (k v)
+                                     (cons (string->symbol (string-downcase k)) v)))
+                        (array . ,identity)
+                        (null . ,(constantly '()))) (json-parsers)))
 
 (: curry (procedure * --> procedure))
 (define (curry fn a)
@@ -23,7 +31,7 @@
 (define (perhaps fn a)
   (if a (fn a) a))
 
-(: upon ((* -> boolean) procedure * -> *))
+(: upon (('a -> boolean) ('a -> 'b) 'a -> (or 'a 'b)))
 (define (upon pred? fn a)
   (if (pred? a) (fn a) a))
 
@@ -86,7 +94,14 @@
   (apply string-append
          (map (curry2 upon symbol? (compose ->string (curry (flip value) ln))) statement)))
 
+(define-type json *)
+(define-type json
+  (or string boolean number float null
+      (list-of json)
+      (list-of (pair symbol json))))
+
 ;;; Get data from a uri and parse it as json.
+(: simple-json-request (string -> json))
 (define (simple-json-request uri)
   (condition-case (with-input-from-request uri #f read-json)
     ((exn i/o net) (begin (display-newline "Connection failed.")
@@ -105,30 +120,29 @@
 ;;; it returns nothing. This bug may be platform related; as of this writing the server system providing the API
 ;;; runs on Windows Server 2016 via IIS 10.0.
 ;;; The second bug involves returning only partial data upon request - no pattern to this bug has been observed.
+(: get-parking-lots (-> json))
 (define (get-parking-lots)
   (value 'parkingareanewlist
          (simple-json-request (string-append "http://parkering.linkoping.se/Parkeringsdata/ParkeringsdataV1.svc/GetParkeringsYtaList/" parking-key "/0"))))
 
 ;;; Only lots tracked by parking lot computer terminals have the parkingspacesavailable key.
+(: computerized (json --> boolean))
 (define (computerized? lot)
   (has-key? 'parkingspacesavailable lot))
 
 ;;; The handicap lots are tracked as separate lots with duplicate names in the data set.
+(: only-has-handicap-spots? (json --> boolean))
 (define (only-has-handicap-spots? lot)
   (equal? '(4) (value 'parkingtypes lot)))
 
 ;;; Electric car lots have a separate lot type, and the downtown parking garages have spaces with charging stations
 ;;; but they are not implemented in the data set.
+(: electric-car-lot? (json --> boolean))
 (define (electric-car-lot? lot)
   (member? 3 (value 'parkingtypes lot)))
 
+(: main (-> undefined))
 (define (main)
-  ;; We want members to be parsed as lowercase symbols, and arrays to be parsed as lists.
-  ;; This is not a legal way to parse json, which requires case-sensitive members
-  ;; but makes for neater scheme code.
-  (json-parsers (append `((member . ,(lambda (k v)
-                                       (cons (string->symbol (string-downcase k)) v)))
-                          (array . ,identity)) (json-parsers)))
   (display-newline "Parking spaces available:")
   (map (compose display-newline (curry format-assoc '(name ": " parkingspacesavailable "/" parkingspaces)))
        (sort-via string-ci<? (curry value 'name)