add isomorphism-compose and isomorphism-thrush

also take away special case in lens-compose for isomorphisms

lens/private/compound/compose.rkt

@@ -7,7 +7,6 @@ require racket/contract
         "../base/main.rkt"
         "../util/rest-contract.rkt"
         "identity.rkt"
-        unstable/lens/isomorphism/base
 
 module+ test
   require rackunit
@@ -29,15 +28,7 @@ provide
 
 
 (define (lens-compose . args)
-  (match args
+  (foldr lens-compose2 identity-lens args))
-    [(list)
-     identity-lens]
-    [(list (make-isomorphism-lens fs invs) ...)
-     (make-isomorphism-lens
-      (apply compose1 fs)
-      (apply compose1 (reverse invs)))]
-    [_
-     (foldr lens-compose2 identity-lens args)]))
 
 
 module+ test
@@ -52,5 +43,3 @@ module+ test
   (check-equal? (lens-view first-of-second-lens test-alist) 'b)
   (check-equal? (lens-set first-of-second-lens test-alist 'B) '((a 1) (B 2) (c 3)))
   (check-eq? (lens-compose) identity-lens)
-  (check-pred isomorphism-lens? (lens-compose (make-isomorphism-lens set->list list->set)
-                                              (make-isomorphism-lens list->vector vector->list)))

unstable/lens/isomorphism.rkt

@@ -1,3 +1,4 @@
 #lang reprovide
 "isomorphism/base.rkt"
+"isomorphism/compound.rkt"
 "isomorphism/data.rkt"

unstable/lens/isomorphism.scrbl

@@ -46,6 +46,16 @@ example, are defined like this:
     (make-isomorphism-lenses string->symbol symbol->string))
 ]}
 
+@defproc[(isomorphism-compose [lens isomorphism-lens?] ...) isomorphism-lens?]{
+Like @racket[lens-compose], but works only on isomorphism lenses, and returns an
+isomorphism lens.
+}
+
+@defproc[(isomorphism-thrush [lens isomorphism-lens?] ...) isomorphism-lens?]{
+Like @racket[lens-thrush], but works only on isomorphism lenses, and returns an
+isomorphism lens.
+}
+
 @deflenses[[string->symbol-lens symbol->string-lens
             number->string-lens string->number-lens
             list->vector-lens vector->list-lens

unstable/lens/isomorphism/compound.rkt

@@ -0,0 +1,18 @@
+#lang sweet-exp racket/base
+
+provide isomorphism-compose
+        isomorphism-thrush
+
+require racket/match
+        "base.rkt"
+
+(define (isomorphism-compose . args)
+  (match args
+    [(list (make-isomorphism-lens fs invs) ...)
+     (make-isomorphism-lens
+      (apply compose1 fs)
+      (apply compose1 (reverse invs)))]))
+
+(define (isomorphism-thrush . args)
+  (apply isomorphism-compose (reverse args)))
+