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{{Infobox programming language
 | name                   = Ratfor
 | released               = {{Start date|1976}}
 | developer              = Brian Kernighan
 | influenced by          = [[Fortran]], [[C (programming language)|C]]
 | website                = [http://sepwww.stanford.edu/doku.php?id=sep:software:ratfor sepwww.stanford.edu]
}}

'''Ratfor''' (short for ''Rational Fortran'') is a [[Programming language|programming language]] implemented as a [[Preprocessor|preprocessor]] for [[Fortran#FORTRAN 66|Fortran 66]]. It provides [[Structured programming|modern control structures]], unavailable in Fortran 66, to replace GOTOs and statement numbers.

== Features ==
Ratfor provides the following kinds of flow-control statements, described by Kernighan and Plauger as "shamelessly stolen from the language [[C (programming language)|C]], developed for the [[Software:Unix|UNIX]] operating system by [[Biography:Dennis Ritchie|D.M. Ritchie]]" ("Software Tools", p.&nbsp;318):

* statement grouping with braces
* '''if-else''', '''while''', '''for''', '''do''', '''repeat-until''', '''break''', '''next'''
* "free-form" statements, i.e., not constrained by Fortran format rules
* <, >, >=, ... in place of .LT., .GT., .GE., ...
* '''include'''
* # comments

For example, the following code
<source lang="c">
if (a > b) {
  max = a
} else {
  max = b
}
</source>
might be translated as
<source lang="fortranfixed">
      IF(.NOT.(A.GT.B))GOTO 1
      MAX = A
      GOTO 2
    1 CONTINUE
      MAX = B
    2 CONTINUE
</source>
The version of Ratfor in ''Software Tools'' is written in Ratfor, as are the sample programs, and inasmuch as its own translation to Fortran is available, it can be ported to any Fortran system. Ratfor source code file names end in .r or .rat.

== History ==
Ratfor was designed and implemented by Brian Kernighan at Bell Telephone Laboratories in 1974, and described in ''Software&mdash;Practice & Experience'' in 1975.  It was used in the book "Software Tools" (Kernighan and Plauger, 1976).

In 1977, at [[Organization:Purdue University|Purdue University]], an improved version of the Ratfor preprocessor was written. It was called Mouse4, as it was smaller and faster than Ratfor. A published document by Dr. [[Biography:Douglas Comer|Douglas Comer]], professor at Purdue, concluded "contrary to the evidence exhibited by the designer of Ratfor, sequential search is often inadequate for production software. Furthermore, in the case of lexical analysis, well-known techniques do seem to offer efficiency while retaining the simplicity, ease of coding and modularity of ad hoc methods." (CSD-TR236).

In comparison to the Ratfor preprocessor on a program of 3000 source lines running on a CDC 6500 system took 185.470 CPU seconds. That was cut by 50% when binary search was used in the Ratfor code. Rewriting the ad hoc lexical scanner using a standard method based on finite automata reduced run time to 12.723 seconds.

With the availability of Fortran 77, a successor named [[Ratfiv]] (Ratfor=rat4 => rat5=Ratfiv) could, with an option /f77, output a more readable Fortran 77 code:
<source lang="fortranfixed">
      IF (A .GT. B) THEN
        MAX = A
      ELSE
        MAX = B
      ENDIF
</source>

Initial Ratfor source code was ported to C in 1985 <ref>{{ cite web|url=http://ratfor.sourcearchive.com/documentation/1.0-11/rat4_8c-source.html |title=Ratfor implementation in C (1985)}}</ref> and improved to produce Fortran 77 code too.<ref>{{ cite web|url=http://sepwww.stanford.edu/doku.php?id=sep:software:ratfor |title=Ratfor77}}</ref> A git tree has been set in 2010 in order to revive ratfor
.<ref>{{ cite web|url=http://gitorious.org/ratfor-revived/c-ratfor |title=Ratfor Git Revived}}</ref>
Although the [[Software:GNU Compiler Collection|GNU C compiler]] had the ability to directly compile a Ratfor file (.r) without keeping a useless intermediate Fortran code (.f) (<code>gcc foo.r</code>), this functionality was lost in version 4 during the move in 2005 from f77 to [[Software:GNU Fortran|GNU Fortran]].<ref>{{ cite web|url=https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24357 |title=gcc lost the ratfor preprocessor}}</ref>

Source packages, .[[Deb (file format)|deb]] or [[Software:RPM Package Manager|src.rpm package]]<ref>{{ cite web|url=http://www.dgate.org/ratfor/SRPMS/ |title=ratfor-1.01-1.src.rpm}}</ref><ref>{{ cite web|url=http://mirror.corbina.net/mandriva/devel/cooker/SRPMS/contrib/release/|title=Another Ratfor source code|url-status=dead|archiveurl=https://archive.today/20130703053450/http://mirror.corbina.net/mandriva/devel/cooker/SRPMS/contrib/release/|archivedate=2013-07-03}} ratfiv or ratfiv source [[Software:RPM Package Manager|rpm package]]</ref> are still available for users who need to compile old Ratfor software on any operating system.

== Ratfiv ==
'''Ratfiv''' is an enhanced version of the Ratfor programming language, a [[Preprocessor|preprocessor]] for [[Fortran]] designed to give it [[C (programming language)|C]]-like capabilities. Fortran was widely used for scientific programming but had very basic [[Control flow|control-flow]] primitives ("do" and "[[Goto|goto]]") and no "[[Macro (computer science)|macro]]" facility which limited its expressiveness.

The name of the language is a pun (''Ratfor'' (RATional FORtran) -> "Rat Four" -> "Rat Five" -> ''RatFiv'').

Ratfiv was developed by Bill Wood at the Institute for Cancer Research, Philadelphia, PA in the early 1980s and released on several DECUS (Digital Equipment Users Group) SIG (Special Interest Group) tapes.  It is based on the original Ratfor by B. Kernighan and P. J. Plauger, with rewrites and enhancements by David Hanson and friends (U. of Arizona), Joe Sventek and Debbie Scherrer ([[Organization:Lawrence Berkeley National Laboratory|Lawrence Berkeley National Laboratory]]).

Ratfiv V2.1 was distributed on the DECUS RSX82a SIG tape.<ref>[http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/rsx/decus/rsx82a/330015/ Ratfiv V2.1 archive]</ref>

== See also ==
* [[Fortran]]
* [[EFL (programming language)|EFL]]

== References ==
{{reflist|30em}}

== External links ==
* [http://sepwww.stanford.edu/doku.php?id=sep:software:ratfor Ratfor]
* [http://sepwww.stanford.edu/doku.php?id=sep:software:ratfor90 Ratfor90]
* [https://web.archive.org/web/20060903163415/http://hopl.murdoch.edu.au/showlanguage.prx?exp=692&language=RATFOR History of Programming Languages: Ratfor]
* [https://docs.lib.purdue.edu/cstech/172 Purdue summary]
* [http://sepwww.stanford.edu/doku.php?id=sep:software:ratfor90 Ratfor90]

[[Category:Fortran programming language family]]

{{Sourceattribution|Ratfor}}