neater

txexpr/base.rkt

@@ -1,9 +1,8 @@
 #lang racket/base
-(require sugar/define sugar/coerce racket/string racket/list xml)
+(require racket/match racket/function racket/format sugar/define sugar/list sugar/coerce racket/string racket/list xml)
 (provide cdata? cdata valid-char? xexpr->string xexpr?) ; from xml
 (provide empty) ; from racket/list
 
-
 ;; Section 2.2 of XML 1.1
 ;; (XML 1.0 is slightly different and more restrictive)
 ;; make private version of my-valid-char to get consistent results with Racket 6.0
@@ -13,76 +12,56 @@
            (<= #xE000  i #xFFFD)
            (<= #x10000 i #x10FFFF))))
 
-
 (define (my-xexpr? x)
-  (or (txexpr? x) (xexpr? x) (my-valid-char? x)))
-
+  ((disjoin txexpr? xexpr? my-valid-char?) x))
 
 (define+provide+safe (txexpr? x [short-only #f])
   predicate/c
-  (and (pair? x)
-       (txexpr-tag? (car x))
-       (let ([result (or (and (empty? (cdr x)) 'short)
-                         ;; separate the my-xexpr? tail match from the rest.
-                         ;; as a recursive operation, it's potentially time-consuming.
-                         (and (andmap my-xexpr? (cddr x))
-                              (cond 
-                                [(txexpr-attrs? (cadr x)) #t]
-                                [(my-xexpr? (cadr x)) 'short]
-                                [else #f])))])
-         (and result (if short-only
-                         (eq? result 'short)
-                         #t)))))
-
+  (match x
+    [(list (? txexpr-tag?) (? my-xexpr?) ...) #true]
+    [(list (? txexpr-tag?) (? txexpr-attrs?) (? my-xexpr?) ...) #:when (not short-only) #true]
+    [_ #false]))
 
 (define+provide+safe (txexpr-short? x)
   predicate/c
   (txexpr? x 'short-only))
 
-
 (define+provide+safe (txexpr-tag? x)
   predicate/c
   (symbol? x))
 
-
 (define+provide+safe (txexpr-attr? x)
   predicate/c
-  (and (list? x)
-       (= 2 (length x))
-       (txexpr-attr-key? (first x))
-       (txexpr-attr-value? (second x))))
-
+  (match x
+    [(list (? txexpr-attr-key?) (? txexpr-attr-value?)) #true]
+    [_ #false]))
 
 (define+provide+safe (txexpr-element? x)
   predicate/c
   (my-xexpr? x))
 
-
 (define+provide+safe (txexpr-attr-key? x)
   predicate/c
   (symbol? x))
 
-
 (define+provide+safe (can-be-txexpr-attr-key? x)
   predicate/c
   (symbolish? x))
 
-
 (define+provide+safe (txexpr-attr-value? x)
   predicate/c
   (string? x))
 
-
 (define+provide+safe (can-be-txexpr-attr-value? x)
   predicate/c
   (stringish? x))
 
-
 (define-syntax-rule (define-plural plural-id pred)
   (define+provide+safe (plural-id x)
     predicate/c
-    (and (list? x) (andmap pred x))))
-
+    (match x
+      [(list (? pred) (... ...)) #true]
+      [_ #false])))
 
 (define-plural txexpr-tags? txexpr-tag?)
 (define-plural txexpr-attrs? txexpr-attr?)
@@ -90,64 +69,42 @@
 (define-plural txexpr-attr-values? txexpr-attr-value?)
 (define-plural list-of-can-be-txexpr-attrs? can-be-txexpr-attrs?)
 
-
 (define+provide+safe (can-be-txexpr-attrs? x)
   predicate/c
-  (for/or ([test (in-list (list txexpr-attr?
-                                txexpr-attrs?
-                                can-be-txexpr-attr-key?
-                                can-be-txexpr-attr-value?))])
-          (test x)))
-
+  ((disjoin txexpr-attr? txexpr-attrs? can-be-txexpr-attr-key? can-be-txexpr-attr-value?) x))
 
 (define (validate-txexpr-attrs x #:context [txexpr-context #f])
-  (define (make-reason)
-    (if (not (list? x)) 
-        (format "because ~v is not a list" x)
-        (let ([bad-attrs (filter (λ (i) (not (txexpr-attr? i))) x)])
-          (format "because ~a ~a" (string-join (map (λ (ba) (format "~v" ba)) bad-attrs) " and ")
-                  (if (> (length bad-attrs) 1)
-                      "are not valid attributes"
-                      "is not in the form '(symbol \"string\")")))))
-  (cond
-    [(and (list? x) (positive? (length x)) (andmap txexpr-attr? x)) x]
-    [else (error (string-append "validate-txexpr-attrs: "
+  (match x
+    [(list (? txexpr-attr? x) ...) x]
+    [_ (raise-argument-error 'validate-txexpr-attrs
+                             (string-append 
                               (if txexpr-context (format "in ~v, " txexpr-context) "")
-                                (format "~v is not a valid list of attributes ~a" x
-                                        (make-reason))))]))
+                              (format "list of attributes, each in the form '(symbol \"string\")")) x)]))
 
 
 (define (validate-txexpr-element x #:context [txexpr-context #f])
-  (cond
-    [(or (string? x) (txexpr? x) (symbol? x)
-         (valid-char? x) (cdata? x)) x]
-    [else (error (string-append "validate-txexpr-element: "
+  (match x
+    [(? (disjoin string? txexpr? symbol? valid-char? cdata?)) x]
+    [_ (raise-argument-error  'validate-txexpr-element
+                              (string-append
                                (if txexpr-context (format "in ~v, " txexpr-context) "")
-                                (format "~v is not a valid element (must be txexpr, string, symbol, XML char, or cdata)" x)))]))
-
+                               "valid element (= txexpr, string, symbol, XML char, or cdata)") x)]))
 
 ;; is it a named x-expression?
-;; todo: rewrite this recurively so errors can be pinpointed (for debugging)
+;; todo: rewrite this recursively so errors can be pinpointed (for debugging)
 (define+provide+safe (validate-txexpr x)
   (any/c . -> . txexpr?)
-  (cond
-    [(txexpr-short? x) x]
-    [(txexpr? x) (and
+  (match x
+    [(cons (? txexpr-tag?) _)
+     (and
       (validate-txexpr-attrs (get-attrs x) #:context x)
       (andmap (λ (e) (validate-txexpr-element e #:context x)) (get-elements x)) x)]
-    [(and (list? x) (symbol? (car x)))
-     (and
-      (andmap (λ (e) (validate-txexpr-element e #:context x)) (get-elements x))
-      (validate-txexpr-attrs (get-attrs x) #:context x))]
-    [(list? x) (error 'validate-txexpr (format "~v is a list but it doesn't start with a symbol" x))]
-    [else (error 'validate-txexpr (format "~v: not an X-expression" x))]))
-
+    [_ (raise-argument-error 'validate-txexpr "valid X-expression" x)]))
 
 (define (txexpr-unsafe tag attrs elements)
-  (cons tag (if (empty? attrs)
-                elements
-                (cons attrs elements))))
-
+  (cons tag (match attrs
+              [(== empty) elements]
+              [_ (cons attrs elements)])))
 
 (define (txexpr-base func-name tag attrs elements)
   (unless (txexpr-tag? tag)
@@ -158,51 +115,42 @@
     (raise-argument-error func-name "txexpr-elements?" elements))
   (txexpr-unsafe tag attrs elements))
 
-
 (define+provide+safe (txexpr tag [attrs null] [elements null])
   ((txexpr-tag?) (txexpr-attrs? txexpr-elements?) . ->* . txexpr?)
   (txexpr-base 'txexpr tag attrs elements))
 
-
 (define+provide+safe (txexpr* tag [attrs null] . elements)
   ((txexpr-tag?) (txexpr-attrs?) #:rest txexpr-elements? . ->* . txexpr?)
   (txexpr-base 'txexpr* tag attrs elements))
 
-
 (define make-txexpr txexpr) ; for backward compatability
 (provide+safe make-txexpr)
 
-
 (define+provide+safe (txexpr->values x)
   (txexpr? . -> . (values txexpr-tag? txexpr-attrs? txexpr-elements?))
-  (if (txexpr-short? x)
-      (values (car x) '() (cdr x))
-      (values (car x) (cadr x) (cddr x))))
-
+  (match x
+    [(? txexpr-short?) (values (car x) '() (cdr x))]
+    [_ (values (car x) (cadr x) (cddr x))]))
 
 (define+provide+safe (txexpr->list x)
   (txexpr? . -> . list?)
   (call-with-values (λ () (txexpr->values x)) list))
 
-
 ;; convenience functions to retrieve only one part of txexpr
 (define+provide+safe (get-tag x)
   (txexpr? . -> . txexpr-tag?)
   (car x))
 
-
 (define+provide+safe (get-attrs x)
   (txexpr? . -> . txexpr-attrs?)
   (define-values (tag attrs elements) (txexpr->values x))
   attrs)
 
-
 (define+provide+safe (get-elements x)
   (txexpr? . -> . txexpr-elements?)
   (define-values (tag attrs elements) (txexpr->values x))
   elements)
 
-
 ;; helpers. we are getting a string or symbol
 (define+provide+safe (->txexpr-attr-key x)
   (can-be-txexpr-attr-key? . -> . txexpr-attr-key?)
@@ -210,15 +158,16 @@
     (raise-argument-error '->txexpr-attr-key "can-be-txexpr-attr-key?" x))
   (->symbol x))
 
-
 (define+provide+safe (->txexpr-attr-value x)
   (can-be-txexpr-attr-value? . -> . txexpr-attr-value?)
   (unless (can-be-txexpr-attr-value? x)
     (raise-argument-error '->txexpr-attr-value "can-be-txexpr-attr-value?" x))
   (->string x))
 
+(define (sublist->attr sublist)
+  (match sublist
+    [(list key value) (list (->txexpr-attr-key key) (->txexpr-attr-value value))]))
 
-(define identity (λ (x) x))
 (define+provide+safe (attrs->hash #:hash-style? [hash-style-priority #f] . items-in)
   (() (#:hash-style? boolean?) #:rest (listof can-be-txexpr-attrs?) . ->* . hash-eq?)
   ;; can be liberal with input because they're all just nested key/value pairs
@@ -231,88 +180,66 @@
   ;; thus reverse the pairs.
   ;; priority-inverted will defeat this assumption, and allow later attributes to overwrite earlier.
   (for/hasheq ([sublist (in-list ((if hash-style-priority
-                                      identity
-                                      reverse) (for/list (#:when (pair? items)
-                                                          [(k ki) (in-indexed items)]
-                                                          [v (in-list (cdr items))]
-                                                          #:when (even? ki))
-                                                         (list k v))))])
-              (let ([key (first sublist)]
-                    [value (second sublist)])
-                (values (->txexpr-attr-key key) (->txexpr-attr-value value)))))
-
+                                      values
+                                      reverse) (slice-at items 2)))])
+              (apply values (sublist->attr sublist))))
 
 (define+provide+safe (hash->attrs attr-hash)
   (hash? . -> . txexpr-attrs?)
-  (map flatten (hash->list attr-hash)))
-
+  (match (hash->list attr-hash)
+    [(list (cons ks vs) ...) (map list ks vs)]))
 
 (define+provide+safe (attrs-have-key? x key)
   ((or/c txexpr-attrs? txexpr?) can-be-txexpr-attr-key? . -> . boolean?)
-  (define attrs (if (txexpr-attrs? x) x (get-attrs x)))
-  (and (assq (->txexpr-attr-key key) attrs) #t))
-
+  (match x
+    [(? txexpr? tx) (and (attr-ref tx key #false) #true)]
+    [_ (attrs-have-key? (txexpr-unsafe '_ x null) key)]))
 
 (define+provide+safe (attr-set tx key value)
   (txexpr? can-be-txexpr-attr-key? can-be-txexpr-attr-value? . -> . txexpr?)
   (attr-set* tx key value))
 
-
 (define+provide+safe (attr-set* tx . kvs)
   ((txexpr?) #:rest (listof (or/c can-be-txexpr-attr-key? can-be-txexpr-attr-value?)) . ->* . txexpr?)
   ;; unlike others, this uses hash operations to guarantee that your attr-set
   ;; is the only one remaining.
   (unless (even? (length kvs))
     (raise-argument-error 'attr-set* "even number of arguments" kvs))
-  (define new-attrs 
-    (hash->attrs
+  (define new-attrs (hash->attrs
                      (apply hash-set* (attrs->hash (get-attrs tx))
-            (append-map (λ (sublist)
-                          (list (->txexpr-attr-key (first sublist))
-                                (->txexpr-attr-value (second sublist))))
-                        (let ([items kvs])
-                          (for/list (#:when (pair? items)
-                                     [(k ki) (in-indexed items)]
-                                     [v (in-list (cdr items))]
-                                     #:when (even? ki))
-                                    (list k v)))))))
+                            (append-map sublist->attr (slice-at kvs 2)))))
   (txexpr-base 'attr-set* (get-tag tx) new-attrs (get-elements tx)))
 
-
 (define+provide+safe (attr-join tx key value)
   (txexpr? can-be-txexpr-attr-key? can-be-txexpr-attr-value? . -> . txexpr?)
-  (define starting-values (string-split (if (attrs-have-key? tx key)
-                                            (attr-ref tx key)
-                                            "")))
+  (define starting-values (string-split (attr-ref tx key "")))
   (attr-set tx key (string-join (append starting-values (list value)) " ")))      
 
-
-(define+provide+safe (attr-ref tx key [failure-result (λ _ (raise (make-exn:fail:contract (format "attr-ref: no value found for key ~v" key) (current-continuation-marks))))])
+(define no-failure-result (gensym)) ; failure-result might be #false
+(define+provide+safe (attr-ref tx key [failure-result no-failure-result])
   ((txexpr? can-be-txexpr-attr-key?) (any/c) . ->* . any)
-  (define result (assq (->txexpr-attr-key key) (get-attrs tx)))
-  (if result
-      (second result)
-      (if (procedure? failure-result)
-          (failure-result)
-          failure-result)))
-
+  (match (assq (->txexpr-attr-key key) (get-attrs tx))
+    [(list _ value) value]
+    [_ (match failure-result
+         [(? procedure?) (failure-result)]
+         [(== no-failure-result) (raise-argument-error 'attr-ref "key that exists in attr list" key)]
+         [_ failure-result])]))
 
 (define+provide+safe (remove-attrs x)
   (txexpr? . -> . txexpr?)
   (let loop ([x x])
     (if (txexpr? x)
         (let-values ([(tag attrs elements) (txexpr->values x)])
-          (cons tag (map loop elements)))
+          (txexpr-unsafe tag null (map loop elements)))
         x)))
 
-
 (define+provide+safe (map-elements proc x)
   (procedure? txexpr? . -> . txexpr?)
+  (let loop ([x x])
     (proc (if (txexpr? x) 
               (let-values ([(tag attrs elements) (txexpr->values x)])
-              (txexpr-unsafe tag attrs (map (λ (e)(map-elements proc e)) elements)))
-            x)))
-
+                (txexpr-unsafe tag attrs (map loop elements)))
+              x))))
 
 ;; function to split tag out of txexpr
 (define deleted-signal (gensym))
@@ -322,35 +249,29 @@
     (raise-argument-error 'splitf-txexpr "txexpr?" tx))
   (define matches null)
   (define (extract! x)
-    (cond
-      [(pred x) ;; store matched item and return processed value
+    (match x
+      [(? pred) ;; store matched item and return processed value
        (set! matches (cons x matches))
        (proc x)]
-      [(txexpr? x) (let-values([(tag attrs elements) (txexpr->values x)]) 
-                     (txexpr tag attrs (filter (λ (e) (not (eq? e deleted-signal)))
+      [(? txexpr?) (let-values ([(tag attrs elements) (txexpr->values x)]) 
+                     (txexpr-unsafe tag attrs (filter-not (λ (e) (eq? e deleted-signal))
                                                           (map extract! elements))))]
-      [else x]))
+      [_ x]))
   (define tx-extracted (extract! tx)) ;; do this first to fill matches
   (values tx-extracted (reverse matches)))
 
-
 (define+provide+safe (findf*-txexpr tx pred)
   (txexpr? procedure? . -> . (or/c #f txexpr-elements?))
   (define-values (_ matches) (splitf-txexpr tx pred))
   (and (pair? matches) matches))
 
-
 (define+provide+safe (findf-txexpr tx pred)
   (txexpr? procedure? . -> . (or/c #f txexpr-element?))
   (define matches (findf*-txexpr tx pred))
   (and matches (car matches)))
 
-
 ;; don't use "![CDATA[...]]" wrapper in HTML, it's not consistent with the spec
-(define (->cdata x)
-  (if (string? x)
-      (cdata #f #f x)
-      x))
+(define (->cdata x) (if (string? x) (cdata #f #f x) x))
 
 ;; but treat CDATA strings correctly anyhow, because that's friendly
 (define (cdata-string? x)
@@ -360,13 +281,13 @@
   (xexpr? . -> . string?)
   (xexpr->string
    (let loop ([x x])
-     (cond
-       [(txexpr? x)
+     (match x
+       [(? txexpr?)
         (let*-values ([(tag attrs elements) (txexpr->values x)]
                       [(proc) (if (memq tag '(script style))
                                   ->cdata
                                   loop)])
           ;; a little faster than `txexpr` since we know the pieces are valid
           (txexpr-unsafe tag attrs (map proc elements)))]
-       [(cdata-string? x) (->cdata x)]
-       [else x]))))
+       [(? cdata-string?) (->cdata x)]
+       [_ x]))))

txexpr/check.rkt

@@ -1,5 +1,16 @@
 #lang racket/base
-(require sugar/define "base.rkt" rackunit)
+(require sugar/define racket/match "base.rkt" rackunit)
+
+(define (stringify-attr attr)
+  (match attr
+    [(list key val) (string-append (symbol->string key) val)]))
+
+(define (sort-attrs x)
+  (match x
+    [(? txexpr?)
+     (let-values ([(tag attr elements) (txexpr->values x)])
+       (txexpr tag (sort attr #:key stringify-attr #:cache-keys? #t string<?) (map sort-attrs elements)))]
+    [_ x]))
 
 (define (txexprs-equal? tx1 tx2)
   ;; txexprs are deemed equal if they differ only in the ordering of attributes.
@@ -10,21 +21,11 @@
   ;; so the whole attr is converted into a single string for sorting, which lets the attr value act as a tiebreaker.
   ;; it doesn't matter that this sort may not be correct (in the sense of a desirable ordering)
   ;; it just needs to be stable (e.g., a certain set of attrs will always sort the same way)
-  (letrec ([stringify-attr (λ (attr) (string-append (symbol->string (car attr)) (cadr attr)))]
-           [sort-attrs (λ (x)
-                         (if (txexpr? x)
-                             (let-values ([(tag attr elements) (txexpr->values x)])
-                               (txexpr tag (sort attr #:key stringify-attr #:cache-keys? #t string<?) (map sort-attrs elements)))
-                             x))])
-    (equal? (sort-attrs tx1) (sort-attrs tx2))))
-
+  (equal? (sort-attrs tx1) (sort-attrs tx2)))
 
 (define+provide+safe (attrs-equal? x1 x2)
   ((or/c txexpr-attrs? txexpr?) (or/c txexpr-attrs? txexpr?) . -> . boolean?)
-  (define attrs-tx1 (if (txexpr-attrs? x1) x1 (get-attrs x1)))
-  (define attrs-tx2 (if (txexpr-attrs? x2) x2 (get-attrs x2)))
-  (txexprs-equal? `(div ,attrs-tx1) `(div ,attrs-tx2)))
-
+  (apply txexprs-equal? (map (λ (x) `(_ ,(if (txexpr-attrs? x) x (get-attrs x)))) (list x1 x2))))
 
 (provide+safe check-txexprs-equal?)
 (define-simple-check (check-txexprs-equal? tx1 tx2)