J3/05-108

To: J3
From: Dan Nagle
Subject: Write CSV files
Date: 2005 Jan 03


CSV files (a/k/a Comma Separated Value) files are
used by spreadsheets and "higher level math" programs
such as Mathematica, MATLAB and Maple.  These programs
provide easy access to graphics and other mathematically
oriented amenities.

Fortran programs can read CSV files via list-directed I/O,
but there's no easy way to write one since the separator
between values is optionally blank or comma (with slash
as a Really Special Case).  Also, there's no guarantee
there will be exactly one separator between each pair of values.
If Fortran programs could easily write CSV files,
the value of using Fortran programs along side spreadsheets etc
would be higher than at present.

Number:

Title: Write CSV files Using LDIO

Submitted By: J3

Status: For Consideration

References: 04-007 10.9

Basic Functionality: Provide a quick and easy way to write files
                     using the CSV format.

Rationale:  List directed input treats the comma as a separator,
            but the separator is optionally blank or comma on output.
            If the separator is blank, one or more blanks may be
            between values.  A way to make the optional separator a comma
            allows an easy way to write CSV files, providing easy
            communications to spreadsheet programs and other higher level
            math programs with built-in graphics, algebraic manipulation,
            and other amenities useful with numeric programs, but absent
            in standard Fortran.

            CSV files are formatted, the simplest format from the user's
            perspective is LD.  So modify LDIO to serve CSV.

Estimated Impact: Rather minor, the RTL must already reckon where
                  to place a separator in LDIO output, and must already
                  recognize comma on LDIO input.

Detailed Specification: Add a mode to the OPEN and/or WRITE statement, say,
                        CSV="YES"|"NO".  When CSV is present
                        with a value of YES, LDIO output will use the comma
                        as the value separator.  When CSV is absent or present
                        with a value of NO, the output separator is processor-
                        dependent (the current case).  Whether the processor
                        will be premitted to write the r*value form is TBD.

                        Optionally, the CSV mode could indicate the character,
                        perhaps other than comma, to be used between values.
                        Again, there must be exactly one such character
                        between each pair of values.  If the separator
                        is allowed to be other than blank or comma, LDIO input
                        is also affected.

                        For completeness, one would like a specifier
                        on the INQUIRE statement to detect when the CSV mode
                        is in effect, but in the interests of simplicity,
                        this paper does not propose to do so.

History: M171 Paper J3/05-108