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Article contents:[[tags:egg]] [[toc:]] == tabular Parsing and formatting of tabular text data such as comma- and delimiter-separated values (CSV and DSV). == Documentation The goal of the tabular library is to provide means of reading and writing tabular text data, such as comma- and delimiter-separated values (CSV and DSV), as well as fixed-width columns. == Procedures === Readers <procedure>reader:: INPUT [DELIMITER: #\,] [EOL: "\n"] [COMMENT-CHAR: #f][NA: #f] [COLUMN-NAMES: #f] [COLUMN-WIDTHS: #f] [RETURN-NAMES: #f] -> READER STREAM</procedure> Constructs a reader procedure for the given input format specification and returns two values: the reader procedure and the input stream. The reader procedure is of the form {{LAMBDA STRM -> RECORD STRM}}. It reads one record from the given input stream and by default returns the record as a list of values and the remainder of the input stream. If optional argument {{RETURN-NAMES}} is true, the record will be returned as an alist where the keys are column names (if {{COLUMN-NAMES}} is provided) or indices, and the values are the column values. * Argument {{INPUT}} is a string or a port. * Argument {{DELIMITER}} specifies the delimiter character (default is {{#\,}}). If its value is #f, then {{COLUMNN-WIDTHS}} must be specified. * Argument {{EOL}} specifies the end-of-line string (default is {{"\n"}}). * Argument {{COMMENT-CHAR}} specifies a comment character: the reader will skip all lines that start with this character (default: none). * Argument {{NA}} specifies a default value to be supplied when a given field is empty (default: none). * Argument {{COLUMN-NAMES}} specifies column names which will be used if {{RETURN-NAMES}} is true (default: none). If {{COLUMN-NAMES}} is the symbol {{'header}} then the column names will be inferred from the first line in the input. * Argument {{COLUMN-WIDTHS}} specifies column widths which will be used if {{DELIMITER}} is not specified (default: none). * Argument {{RETURN-NAMES}} specifies that each returned record will have the form of an alist with column name and value pairs. If {{COLUMN-NAMES}} is not provided, the column index will be used as key instead. <procedure>reader*:: INPUT [DELIMITER: #\,] [EOL: "\n"] [COMMENT-CHAR: #f][NA: #f] [COLUMN-NAMES: #f] [COLUMN-WIDTHS: #f] [RETURN-NAMES: #f] -> READER</procedure> Constructs a reader generator procedure for the given input format specification and returns the reader procedure. The reader procedure is of the form {{LAMBDA () -> RECORD}}. It reads one record from the given input stream and by default returns the record as a list of values. If optional argument {{RETURN-NAMES}} is true, the record will be returned as an alist where the keys are column names (if {{COLUMN-NAMES}} is provided) or indices, and the values are the column values. * Argument {{INPUT}} is a string or a port. * Argument {{DELIMITER}} specifies the delimiter character (default is {{#\,}}). If its value is #f, then {{COLUMNN-WIDTHS}} must be specified. * Argument {{EOL}} specifies the end-of-line string (default is {{"\n"}}). * Argument {{COMMENT-CHAR}} specifies a comment character: the reader will skip all lines that start with this character (default: none). * Argument {{NA}} specifies a default value to be supplied when a given field is empty (default: none). * Argument {{COLUMN-NAMES}} specifies column names which will be used if {{RETURN-NAMES}} is true (default: none). If {{COLUMN-NAMES}} is the symbol {{'header}} then the column names will be inferred from the first line in the input. * Argument {{COLUMN-WIDTHS}} specifies column widths which will be used if {{DELIMITER}} is not specified (default: none). * Argument {{RETURN-NAMES}} specifies that each returned record will have the form of an alist with column name and value pairs. If {{COLUMN-NAMES}} is not provided, the column index will be used as key instead. === Writers <procedure>writer:: OUTPUT [DELIMITER: #,] [COLUMN-WIDTHS: #f] [ENDLINE: "\n"] -> WRITER</procedure> Constructs a writer procedure that writes out records according to the given output specification. The writer procedure is of the form {{LAMBDA RECORDS -> UNIT}}. Each record is represented as a list. * Argument {{OUTPUT}} is a string file name or a port. * Argument {{DELIMITER}} specifies the delimiter character (default is {{#\,}}). If its value is #f, then {{COLUMNN-WIDTHS}} must be specified. * Argument {{ENDLINE}} specifies the end-of-line string (default is {{"\n"}}). * Argument {{COLUMN-WIDTHS}} specifies column widths which will be used if {{DELIMITER}} is not specified (default: none). == Examples <enscript highlight="scheme"> (import tabular) (define (stream->list proc strm) (let recur ((ax '()) (strm strm)) (let ((value.strm (proc strm))) (if (eof-object? value.strm) (reverse ax) (recur (cons (car value.strm) ax) (cadr value.strm)) )) )) ;; Uses a reader generator to print all records in the given input string (let-values (((proc strm) (call-with-input-string "\"Test \n1\"|Test 2|Test 3\nTest 4|Test 5\n" (lambda (port) (reader port delimiter: #\|))))) (print (stream->list proc strm))) ;; Prints all the records from the given file, where column names are inferred from the first line ;; and each field in a record is prefixed by its column name (let ((input (open-input-file "file.csv"))) (let-values (((proc strm) (reader input delimiter: #\, column-names: 'header return-names: #t))) (let ((lst (stream->list proc strm))) (close-input-port input) (pretty-print lst) )) ) ;; Prints the first record of the given file (let ((input (open-input-file "file.csv")) (gen (reader* input delimiter: #\,))) (print (gen)) ) ;; Writes the given records to a string port (call-with-output-string (lambda (port) (let ((out (writer port))) (out (list "Test 1" "Test 2" "Test 3") (list "Test 4" "Test 5" ))) )) </enscript> == Repository [[https://github.com/iraikov/chicken-tabular|https://github.com/iraikov/chicken-tabular]] == Version history * 1.4 : Fix for return-names in reader generator [thanks to Vasilij Schneidermann for reporting] * 1.3 : Fix for return-names [thanks to Vasilij Schneidermann for reporting] * 1.2 : Fix for escaped double quotes [thanks to Matt Welland for reporting] * 1.1 : Fix to tests [thanks to Mario for reporting] * 1.0 : Initial release == License Copyright 2019-2021 Ivan Raikov 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/. Description of your changes:

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