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  2. csv
    1. Description
    2. Library Procedures
      1. Parsing Procedures: Preliminaries
      2. Parsing Procedures: csv-char-list
      3. Parsing Procedures: csv-string
      4. Parsing Procedures: csv
      5. Formatting procedures
    3. Requires
    4. Version History
    5. License

csv

Description

The csv library contains procedures for parsing and formatting of comma-separated values (CSV) as described in RFC 4180. There are several differences with the RFC:

See also csv-xml.

Library Procedures

[procedure] (csv-record? X) => BOOL

Returns #t if the given object is a csv-record, #f otherwise.

[procedure] (list->csv-record LIST) => CSV-RECORD

Takes in a list of values and creates a csv-record object.

[procedure] (csv-record->list CSV-RECORD) => LIST

Returns the list of values contained in the given csv-record object.

Parsing Procedures: Preliminaries

The parsing procedures in csv come in two flavors: generic and specialized for operations on lists of characters and strings.

The <CSV> typeclass defined in module csv is intended to provide abstraction over different kinds of input sequences, e.g. character lists, strings, streams, etc. <CSV> inherits from <CoreABNF>, which provides the core parsing primitives used to build the CSV grammar parser (see the abnf library for more information).

The procedures in modules csv-char-list and csv-string operate on lists of characters and strings, respectively. They do not require the instantiaton of type classes and are meant to provide "turn key" parsing.

Parsing Procedures: csv-char-list

[procedure] (csv-parser [DELIMITER]) => PARSER

When invoked, csv-parser returns a parser procedure takes in a list of characters and returns a list of the form:

 ((<#csv-record (FIELD1 FIELD2 ...)>) (<#csv-record ... >))

where FIELD represents the field values in a record.

Optional arguments DELIMITER is the field delimiter character, if other than comma.

Parsing Procedures: csv-string

[procedure] (csv-parser [DELIMITER]) => PARSER

When invoked, csv-parser returns a parser procedure takes in a string and returns a list of the form:

 ((<#csv-record (FIELD1 FIELD2 ...)>) (<#csv-record ... >))

where FIELD represents the field values in a record.

Optional arguments DELIMITER is the field delimiter character, if other than comma.

Parsing Procedures: csv

[procedure] (make-parser CSV-INSTANCE) => (LAMBDA [DELIMITER]) => PARSER

Once applied to an instance of the <CSV> typeclass, make-parser returns a constructor for the CSV parsing procedure. Optional argument DELIMITER specifies the field delimiter (comma by default). DELIMITER can be a character, or an SRFI-14 character set. The returned procedure takes in an input stream and returns a list of the form:

 ((<#csv-record (FIELD1 FIELD2 ...)>) (<#csv-record ... >))

where FIELD represents the field values in a record.

The following example illustrates the creation of an instance of <CSV> specialized for character lists.

(require-extension typeclass input-classes abnf csv)

(define char-list-<Input>
  (make-<Input> null? car cdr))

(define char-list-<Token>
  (Input->Token char-list-<Input>))

(define char-list-<CharLex>
  (Token->CharLex char-list-<Token>))

(define char-list-<CoreABNF>
  (CharLex->CoreABNF char-list-<CharLex>))

(define char-list-<CSV>
  (CoreABNF->CSV char-list-<CoreABNF> ))

(define parse-csv ((make-parser char-list-<CSV>) #\|))

(parse-csv (string->list "a|b|c"))

(map csv-record->list (parse-csv (string->list "a|b|c")))

 ==> (("a" "b" "c"))

Formatting procedures

[procedure] (make-format [DELIMITER]) => FORMAT-CELL * FORMAT-RECORD * FORMAT-CSV

Returns procedures for outputting individual field values, CSV records, and lists of CSV records, where each list is printed on a separate line.

Procedure FORMAT-CELL takes in a value, obtains its string representation via format, and surrounds the string with quotes, if it contains characters that need to be escaped (such as quote characters, the delimiter character, or newlines).

Procedure FORMAT-RECORD takes in a record of type csv-record and returns its string representation, based on the strings produced by FORMAT-CELL and the delimiter character.

Procedure FORMAT-CSV takes in a list of csv-record objects and produces a string representation using FORMAT-RECORD.

Example:

(use csv)

(define-values (fmt-cell fmt-record fmt-csv) (make-format ";"))

(fmt-cell "hello") => "hello"

;; This is quoted because it contains delimiter-characters
(fmt-cell "one;two;three") => "\"one;two;three\""

;; This is quoted because it contains quotes, which are then doubled for escaping
(fmt-cell "say \"hi\"") => "\"say \"\"hi\"\"\""

;; Converts one line at a time (useful when converting data in a streaming manner)
(fmt-record (list->csv-record '("hi there" "let's say \"hello world\" again" "until we are bored")))
=> "hi there;\"let's say \"\"hello world\"\" again\";until we are bored"

;; And an example of how to quickly convert a list of lists 
;; to a CSV string containing the entire CSV file
(fmt-csv (map list->csv-record
              '(("one" "two")
                ("and another \"line\"" "of csv stuff"))))
=> "one;two\r\n\"and another \"\"line\"\"\";of csv stuff\r\n"

Requires

Version History

License

 
 Copyright 2009-2013 Ivan Raikov and the Okinawa Institute of Science and Technology.
 This program is free software: you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation, either version 3 of the
 License, or (at your option) any later version.
 This program is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 General Public License for more details.
 A full copy of the GPL license can be found at
 <http://www.gnu.org/licenses/>.