bug eliminated from _words_ reading

collects/2htdp/batch-io.ss

@@ -9,22 +9,22 @@
 (provide
  ;; all reader functions consume the name of a file f:
  ;; -- f must be a file name (string) in the same folder as the program 
-
+ 
  read-file ;; String -> String
  ;; read the specified file as a string
  
  read-as-1strings ;; String -> [Listof 1String]
  ;; read the specified file as a list of 1strings (characters)
-
+ 
  read-as-lines ;; String -> [Listof String]
  ;; read the specified file as a list of strings, one per line
  
  read-as-words ;; String -> [Listof String]
  ;; read the specified file as a list of white-space separated tokens
-
+ 
  read-as-words/line ;; String -> [Listof [Listof String]]
  ;; read the specified file as a list of lines, each line as a list of words
-
+ 
  read-as-csv ;; String -> [Listof [Listof (U Any)]]
  ;; -- f must be formated as a a file with comma-separated values (Any)
  ;; read the specified file as a list of lists---one per line---of values (Any)
@@ -33,7 +33,7 @@
  ;; -- f must be formated as a a file with comma-separated values (Any)
  ;; read the specified file as a file of comma-separated values, apply the second
  ;; argument to each row, i.e., list of CSV on one line 
-
+ 
  write-file ;; String String -> Boolean
  ;; write the second argument to specified file in the same folder as the program
  ;; produce false, if f exists
@@ -61,13 +61,19 @@
   (read-chunks f read-line reverse))
 
 (def-reader (read-as-words f)
-  (define lines (read-chunks f read-line reverse))
-  (foldr (lambda (f r) (append (split f) r)) '() lines))
+  (read-as-words/line/internal f append))
 
 (def-reader (read-as-words/line f)
   ;; String -> [Listof [Listof String]]
   ;; read the specified file as a list of lines, each line as a list of words
-  (map split (read-chunks f read-line reverse)))
+  (read-as-words/line/internal f cons))
+
+(define (read-as-words/line/internal f combine)
+  (define lines (read-chunks f read-line (lambda (x) x)))
+  (foldl (lambda (f r)
+           (define fst (filter (compose not (curry string=? "")) (split f)))
+           (if (empty? fst) r (combine fst r)))
+         '() lines))
 
 (def-reader (read-as-csv f)
   (read-as-csv/func f))

collects/2htdp/tests/batch-io.ss

@@ -45,6 +45,19 @@ eos
 (write-file file test2)
 (check-equal? (read-as-1strings file) as-1strings2 "as-lines 2")
 
+(define test2-a-as-list '("test1" "" "test2"))
+
+(define test2-a
+  (apply string-append 
+         (list (first test2-as-list)
+               (string #\newline)
+               (string #\newline)
+               (second test2-as-list))))
+
+(write-file file test2-a)
+(check-equal? (read-as-lines file) test2-a-as-list "as-lines 2-a")
+(check-equal? (read-as-words file) '("test1" "test2") "as-words 2-a")
+
 (define test3 #<< eos
  word1, word2 
  word3, word4
@@ -53,13 +66,13 @@ eos
 
 (write-file file test3)
 (check-equal? (read-as-words file) '("word1," "word2" "word3," "word4")
-  "as-words")
+              "as-words")
 (check-equal? (read-as-words/line file) '(("word1," "word2") ("word3," "word4"))
-  "as-words")
+              "as-words")
 (check-equal? (read-as-csv file) '(("word1" "word2") ("word3" "word4"))
-  "as-cvs 1")
-(check-equal? (read-as-csv/rows file length) '(2 2)
-  "as-words/rows")
+              "as-cvs 1")
+(check-equal? (read-as-csv/rows file length) '(2 2) 
+              "as-csv/rows")
 
 
 (check-exn exn:fail:contract? (lambda () (write-file 0 1)))