Add json-object-contains-key?, json-list-length, and json-key-not-found.

Update README accordingly and with add examples.

8 files changed, 109 insertions, 58 deletions

diff --git a/lib/zambyte/meta/180.scm b/lib/zambyte/meta/180.scm
index 735a895..71ee1a8 100644
--- a/lib/zambyte/meta/180.scm
+++ b/lib/zambyte/meta/180.scm
@@ -2,17 +2,6 @@
 	(srfi 1)
 	(srfi 2))
 (begin
-  (define (string->json str)
-    (call-with-port (open-input-string str)
-      (lambda (port)
-	(json-read port))))
-
-  (define (json->string json)
-    (call-with-port (open-output-string)
-      (lambda (port)
-	(json-write json port)
-	(get-output-string port))))
-
   (define (json-object . pairs)
     (map
      (lambda (pair)
@@ -25,11 +14,27 @@
   (define json-list? vector?)
   ;; json-null? already defined in srfi 180
 
+  (define (json-object-contains-key? obj key)
+    (and (assoc (string->symbol key) obj) #t))
+
+  (define (string->json str)
+    (call-with-port (open-input-string str)
+      (lambda (port)
+	(json-read port))))
+
+  (define (json->string json)
+    (call-with-port (open-output-string)
+      (lambda (port)
+	(json-write json port)
+	(get-output-string port))))
+
   (define (json-object-ref json key)
-    (and-let* ((pair (assoc (string->symbol key) json)))
-      (cdr pair)))
+    (or (and-let* ((pair (assoc (string->symbol key) json)))
+	  (cdr pair))
+	((json-key-not-found))))
 
   (define json-list-ref vector-ref)
+  (define json-list-length vector-length)
 
   (define (json-object->alist json)
     (map
diff --git a/lib/zambyte/meta/chibi.scm b/lib/zambyte/meta/chibi.scm
index 49f72f6..fc8e942 100644
--- a/lib/zambyte/meta/chibi.scm
+++ b/lib/zambyte/meta/chibi.scm
@@ -2,9 +2,6 @@
 	(srfi 1)
 	(srfi 2))
 (begin
-  ;; json->string already defined in chibi json
-  ;; string->json already defined in chibi json
-
   (define (json-object . pairs)
     (map
      (lambda (pair)
@@ -16,14 +13,22 @@
   (define json-object? list?)
   (define json-list? vector?)
 
+  (define (json-object-contains-key? obj key)
+    (and (assoc (string->symbol key) obj) #t))
+
   (define (json-null? obj)
     (eq? obj json-null))
 
+  ;; json->string already defined in chibi json
+  ;; string->json already defined in chibi json
+
   (define (json-object-ref json key)
-    (and-let* ((pair (assoc (string->symbol key) json)))
-      (cdr pair)))
+    (or (and-let* ((pair (assoc (string->symbol key) json)))
+	  (cdr pair))
+	((json-key-not-found))))
 
   (define json-list-ref vector-ref)
+  (define json-list-length vector-length)
 
   (define (json-object->alist json)
     (map
diff --git a/lib/zambyte/meta/gauche.scm b/lib/zambyte/meta/gauche.scm
index 733599a..3ab2062 100644
--- a/lib/zambyte/meta/gauche.scm
+++ b/lib/zambyte/meta/gauche.scm
@@ -2,6 +2,18 @@
 	(rfc json)
 	(srfi 1))
 (begin
+  (define json-object list)
+  (define json-list vector)
+  (define json-null 'null)
+  (define json-object? list?)
+  (define json-list? vector?)
+
+  (define (json-null? obj)
+    (eq? obj json-null))
+
+  (define (json-object-contains-key? obj key)
+    (and (assoc key obj) #t))
+
   (define array-handler list->vector)
   (define object-handler identity)
   (define (special-handler x)
@@ -17,16 +29,12 @@
       (parse-json-string str)))
 
   (define json->string construct-json-string)
-  (define json-object list)
-  (define json-list vector)
-  (define json-null 'null)
-  (define json-object? list?)
-  (define json-list? vector?)
 
-  (define (json-null? obj)
-    (eq? obj json-null))
+  (define (json-object-ref json key)
+    (or (assoc-ref json key)
+	((json-key-not-found))))
 
-  (define json-object-ref assoc-ref)
   (define json-list-ref vector-ref)
+  (define json-list-length vector-length)
   (define json-object->alist identity)
   (define json-list->list vector->list))
diff --git a/lib/zambyte/meta/gerbil.scm b/lib/zambyte/meta/gerbil.scm
index 00f7b0e..8d545ef 100644
--- a/lib/zambyte/meta/gerbil.scm
+++ b/lib/zambyte/meta/gerbil.scm
@@ -1,23 +1,29 @@
 (import (std text json)
 	(scheme hash-table))
 (begin
-  (define string->json string->json-object)
-  (define json->string json-object->string)
-
   (define (json-object . pairs)
     (alist->hash-table pairs equal?))
 
   (define json-list list)
-  (define json-null #!void)
+  (define json-null (if #f #f))
   (define json-object? hash-table?)
   (define json-list? list?)
 
   (define (json-null? obj)
     (eq? obj json-null))
 
+  (define (json-object-contains-key? json key)
+    (hash-table-contains? json key))
+
+  (define string->json string->json-object)
+  (define json->string json-object->string)
+
   (define (json-object-ref json key)
-    (hash-table-ref json (string->symbol key)))
+    (or (and (json-object-contains-key? json key)
+	     (hash-table-ref json key))
+	((json-key-not-found))))
 
   (define json-list-ref list-ref)
+  (define json-list-length length)
   (define json-object->alist hash-table->alist)
   (define json-list->list values))
diff --git a/lib/zambyte/meta/guile.scm b/lib/zambyte/meta/guile.scm
index cbd998b..96968d6 100644
--- a/lib/zambyte/meta/guile.scm
+++ b/lib/zambyte/meta/guile.scm
@@ -2,8 +2,6 @@
 	(srfi 1)
 	(srfi 2))
 (begin
-  (define string->json json-string->scm)
-  (define json->string scm->json-string)
   (define json-object list)
   (define json-list vector)
   (define json-null 'null)
@@ -13,10 +11,18 @@
   (define (json-null? obj)
     (eq? obj json-null))
 
+  (define (json-object-cointains-key? obj key)
+    (and (assoc key obj) #t))
+
+  (define string->json json-string->scm)
+  (define json->string scm->json-string)
+
   (define (json-object-ref json key)
-    (and-let* ((pair (assoc key json)))
-      (cdr pair)))
+    (or (and-let* ((pair (assoc key json)))
+	  (cdr pair))
+	((json-key-not-found))))
 
   (define json-list-ref vector-ref)
+  (define json-list-length vector-length)
   (define json-object->alist values)
   (define json-list->list vector->list))
diff --git a/lib/zambyte/meta/json.sld b/lib/zambyte/meta/json.sld
index 0313516..58479e8 100644
--- a/lib/zambyte/meta/json.sld
+++ b/lib/zambyte/meta/json.sld
@@ -1,21 +1,25 @@
 (define-library (zambyte meta json)
   ;; portable
   (export json-ref
-	  json-value?)
-  ;; non-portable
-  (export string->json
-	  json->string
+	  json-value?
 
-	  json-object
+	  json-key-not-found)
+  ;; non-portable
+  (export json-object
 	  json-list
 	  json-null
 
 	  json-object?
 	  json-list?
 	  json-null?
+	  json-object-contains-key?
+
+	  string->json
+	  json->string
 
 	  json-object-ref
 	  json-list-ref
+	  json-list-length
 
 	  json-object->alist
 	  json-list->list)
@@ -36,7 +40,9 @@
 	  (string? obj)
 	  (json-null? obj)
 	  (json-list? obj)
-	  (json-object? obj))))
+	  (json-object? obj)))
+
+    (define json-key-not-found (make-parameter (lambda () (values)))))
   ;; non-portable
   (cond-expand
    ((and (library (macduffie json)) (srfi 69))
diff --git a/lib/zambyte/meta/macduffie.scm b/lib/zambyte/meta/macduffie.scm
index f80ea18..8a42183 100644
--- a/lib/zambyte/meta/macduffie.scm
+++ b/lib/zambyte/meta/macduffie.scm
@@ -2,9 +2,6 @@
 		(json-null md:json-null))
 	(srfi 69))
 (begin
-  (define string->json json-read-string)
-  (define json->string json-write-string)
-
   (define (json-object . pairs)
     (alist->hash-table pairs))
 
@@ -13,7 +10,16 @@
   (define json-object? hash-table?)
   (define json-list? list?)
   ;; json-null? already defined in macduffie json
-  (define json-object-ref hash-table-ref)
+  (define json-object-contains-key? hash-table-exists?)
+  (define string->json json-read-string)
+  (define json->string json-write-string)
+
+  (define (json-object-ref json key)
+    (or (and (hash-table-exists? json key)
+	     (hash-table-ref json key))
+	((json-key-not-found))))
+
   (define json-list-ref list-ref)
+  (define json-list-length length)
   (define json-object->alist hash-table->alist)
   (define json-list->list values))
diff --git a/lib/zambyte/meta/sagittarius.scm b/lib/zambyte/meta/sagittarius.scm
index 3b5a741..97deb0b 100644
--- a/lib/zambyte/meta/sagittarius.scm
+++ b/lib/zambyte/meta/sagittarius.scm
@@ -2,17 +2,6 @@
 	(srfi 1)
 	(srfi 2))
 (begin
-  (define (string->json str)
-    (call-with-port (open-input-string str)
-      (lambda (port)
-	(json-read port))))
-
-  (define (json->string json)
-    (call-with-port (open-output-string)
-      (lambda (port)
-	(json-write json port)
-	(get-output-string port))))
-
   (define (json-object . pairs)
     (if (eq? (*json-map-type*) 'vector)
 	(apply vector pairs)
@@ -38,13 +27,33 @@
   (define (json-null? obj)
     (eq? obj json-null))
 
+  (define (json-object-contains-key? obj key)
+    (and (assoc key (json-object->alist obj)) #t))
+
+  (define (string->json str)
+    (call-with-port (open-input-string str)
+      (lambda (port)
+	(json-read port))))
+
+  (define (json->string json)
+    (call-with-port (open-output-string)
+      (lambda (port)
+	(json-write json port)
+	(get-output-string port))))
+
   (define (json-object-ref json key)
-    (and-let* ((pair (assoc key (json-object->alist json))))
-      (cdr pair)))
+    (or (and-let* ((pair (assoc key (json-object->alist json))))
+	  (cdr pair))
+	((json-key-not-found))))
 
   (define (json-list-ref json index)
     (list-ref (json-list->list json) index))
 
+  (define (json-list-length json)
+    (if (eq? (*json-map-type*) 'vector)
+	(length json)
+	(vector-length json)))
+
   (define (json-object->alist json)
     (if (eq? (*json-map-type*) 'vector)
 	(vector->list json)