136 lines
4.7 KiB
Scheme
136 lines
4.7 KiB
Scheme
#lang scheme
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(require (for-syntax syntax/parse) srfi/13 htdp/error "private/csv/csv.ss")
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;; todo?
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;; -- export tokenization?
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;; -----------------------------------------------------------------------------
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(provide
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;; all reader functions consume the name of a file f:
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;; -- f must be a file name (string) in the same folder as the program
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read-file ;; String -> String
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;; read the specified file as a string
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read-as-1strings ;; String -> [Listof 1String]
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;; read the specified file as a list of 1strings (characters)
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read-as-lines ;; String -> [Listof String]
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;; read the specified file as a list of strings, one per line
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read-as-words ;; String -> [Listof String]
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;; read the specified file as a list of white-space separated tokens
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read-as-words/line ;; String -> [Listof [Listof String]]
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;; read the specified file as a list of lines, each line as a list of words
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read-as-csv ;; String -> [Listof [Listof (U Any)]]
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;; -- f must be formated as a a file with comma-separated values (Any)
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;; read the specified file as a list of lists---one per line---of values (Any)
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read-as-csv/rows ;; String ([Listof Any] -> X) -> [Listof X]
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;; -- f must be formated as a a file with comma-separated values (Any)
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;; read the specified file as a file of comma-separated values, apply the second
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;; argument to each row, i.e., list of CSV on one line
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write-file ;; String String -> Boolean
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;; write the second argument to specified file in the same folder as the program
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;; produce false, if f exists
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;; produce true, if f doesn't exist
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)
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;; -----------------------------------------------------------------------------
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(define-syntax-rule
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(def-reader (name f s ...) body ...)
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(define (name f s ...)
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(check-file f 'name)
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(let ()
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body ...)))
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;; --- exported functions --
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(def-reader (read-file f)
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(list->string (read-chunks f read-char drop-last-newline)))
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(def-reader (read-as-1strings f)
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(map string (read-chunks f read-char drop-last-newline)))
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(def-reader (read-as-lines f)
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(read-chunks f read-line reverse))
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(def-reader (read-as-words f)
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(read-as-words/line/internal f append))
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(def-reader (read-as-words/line f)
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;; String -> [Listof [Listof String]]
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;; read the specified file as a list of lines, each line as a list of words
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(read-as-words/line/internal f cons))
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(define (read-as-words/line/internal f combine)
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(define lines (read-chunks f read-line (lambda (x) x)))
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(foldl (lambda (f r)
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(define fst (filter (compose not (curry string=? "")) (split f)))
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(if (empty? fst) r (combine fst r)))
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'() lines))
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(def-reader (read-as-csv f)
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(read-as-csv/func f))
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(def-reader (read-as-csv/rows f row)
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(check-proc 'read-as-cvs row 1 "one argument" "row")
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(read-as-csv/func f row))
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;; -----------------------------------------------------------------------------
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;; writer
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(define (write-file f str)
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(check-arg 'write-file (string? f) "string (name of file)" "first" f)
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(check-arg 'write-file (string? str) "string" "second" str)
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(let ([result (not (file-exists? f))])
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(with-output-to-file f
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(lambda () (printf "~a" str))
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#:exists 'truncate)
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result))
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;; -----------------------------------------------------------------------------
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;; auxiliaries
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;; String [([Listof X] -> Y)] -> [Listof Y]
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(define (read-as-csv/func f [row (lambda (x) x)])
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(local ((define (reader o)
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(make-csv-reader o '((strip-leading-whitespace? . #t)
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(strip-trailing-whitespace? . #t)))))
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(map row (call-with-input-file f (compose csv->list reader)))))
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;; String (-> X) ([Listof X] -> [Listof X]) -> [Listof X]
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;; read a file as a list of X where process-accu is applied to accu when eof
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(define (read-chunks f read-chunk process-accu)
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(with-input-from-file f
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(lambda ()
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(let loop ([accu '()])
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(define nxt (read-chunk))
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(if (eof-object? nxt) (process-accu accu) (loop (cons nxt accu)))))))
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;; [Listof Char] -> [Listof Char]
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(define (drop-last-newline accu)
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(reverse (if (char=? (car accu) #\newline) (cdr accu) accu)))
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;; String[file name] Symbol -> Void
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;; effect: ensure that f is a file in current directory or report error for t
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(define (check-file f t)
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(check-arg t (string? f) "string" "first" f)
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(check-arg t (file-exists? f) "name of file in program's folder" "first" f))
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;; split : String [Regexp] -> [Listof String]
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;; splits a string into a list of substrings using the given delimiter
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;; (white space by default)
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(define (split str [ptn #rx"[ ]+"])
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(regexp-split ptn (string-trim-both str)))
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;; split-lines : String -> Listof[String]
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;; splits a string with newlines into a list of lines
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(define (split-lines str)
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(map string-trim-both (split str "\r*\n")))
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