[honu] make dot a fixture so that assignment can work: v.x := 5

collects/honu/core/private/honu2.rkt

@@ -179,6 +179,31 @@
        (values out #'rest #t)])))
 
 (provide honu-dot)
+(define-honu-fixture honu-dot
+  (lambda (left rest)
+    (syntax-parse rest #:literal-sets (cruft)
+                       #:literals (honu-assignment)
+      [(_ name:identifier honu-assignment argument:honu-expression . more)
+       (with-syntax ([left left])
+         (values #'(%racket
+                     (let ([left* left])
+                       (cond
+                         [(honu-struct? left*)
+                          (honu-struct-set! left* 'name argument.result)]
+                         [(object? left*) (error 'set "implement set for objects")])))
+                 #'more))]
+      [(_ name:identifier . more)
+       (with-syntax ([left left])
+         (values #'(%racket
+                     (let ([left* left])
+                       (cond
+                         [(honu-struct? left*) (let ([use (honu-struct-get left*)])
+                                                 (use left* 'name))]
+                         [(object? left*) (get-field name left*)]
+                         ;; possibly handle other types of data
+                         [else (error 'dot "don't know how to deal with ~a (~a)" 'left left*)])))
+                 #'more))])))
+#;
 (define-honu-operator/syntax honu-dot 10000 'left
   (lambda (left right)
     (debug "dot left ~a right ~a\n" left right)

collects/honu/core/private/struct.rkt

@@ -12,10 +12,21 @@
 (define-values (honu-struct honu-struct? honu-struct-get)
                (make-struct-type-property 'honu-struct))
 
+(define-values (honu-struct-mutable honu-struct-mutable? honu-struct-mutate)
+               (make-struct-type-property 'honu-struct-mutable))
+
 (define-for-syntax (make-accessors name fields)
   (for/list ([field fields])
     (format-unique-id name "~a-~a" name field)))
 
+(define-for-syntax (make-mutators name fields)
+  (for/list ([field fields])
+    (format-unique-id name "set-~a-~a!" name field)))
+
+(provide honu-struct-set!)
+(define (honu-struct-set! instance name value)
+  ((honu-struct-mutate instance) instance name value))
+
 (provide honu-structure)
 (define-honu-syntax honu-structure
   (lambda (code context)
@@ -23,9 +34,18 @@
       [(_ name:id (#%braces fields:identifier-comma-list) . rest)
        (define out
          (with-syntax ([(fields.name/accessor ...)
-                        (make-accessors #'name (syntax->list #'(fields.name ...)))])
+                        (make-accessors #'name (syntax->list #'(fields.name ...)))]
+                       [(fields.name/mutator ...)
+                        (make-mutators #'name (syntax->list #'(fields.name ...)))])
            #'(%racket (struct name (fields.name ...)
                               #:transparent
+                              #:mutable
+                              #:property honu-struct-mutable
+                                (lambda (instance name value)
+                                  (case name
+                                    [(fields.name) (fields.name/mutator instance value)]
+                                    ...
+                                    [else (error 'dot "no such field name ~a" name)]))
                               #:property honu-struct (lambda (instance name)
                                                        (case name
                                                          [(fields.name) (fields.name/accessor instance)]