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From |
Joly.Patrick@ic.gc.ca |

To |
statalist@hsphsun2.harvard.edu |

Subject |
RE: st: RE: About data transformation |

Date |
Fri, 14 Feb 2003 15:18:53 -0500 |

I originally wrote > Humm, you mean that issuing > > version 7.0: save filename6, old > > in Stata 8 will not yield the same result as issuing > > save filename6, old > > in Stata 7? To which Vince (vwiggins@stata.com) replied, > Interesting thought, but the answer is no. > > The goal of the -version- statement is backward compatibility > -- that is to > say, the ability of new versions of Stata to run do- and > ado-files written > with old syntax. Stata's language is evolving and we > sometimes make changes > that would cause old syntax to break or produce different > results. You don't > want your programs to break or your results to change; so, if > you are using > Stata 8, you should put -version 8- at the top of your > do-files, at the top of > your class-files, or right after the -program ...- statement of your > ado-files. Stata's promise to you is that your do-file or > program will > continue to work and produce the same results as new versions > of Stata are > released. It's not really a promise, we have occasionally > made changes where > strict version control could not be maintained -- such as the > introduction of > time-series operators in Stata 6 -- but such occasions are > the exception. > > What Patrick suggests, is forward compatibility -- the > ability of a newer > version of Stata to mimic an older version -- and that is not > something > provided under version control. Sometimes forward and > backward compatibility > mean the same thing, but not in this case. Thanks Vince for the explanation but I don't get it. You define backward compatibility as "the ability of new versions of Stata to run do- and ado-files written with old syntax". Then you suggest that the example I provided -- i.e. of saving a dataset as a Stata 6 data file, in Stata 8 -- is an instance of *forward* compatibility which you define as "the ability of a newer version of Stata to mimic an older version". I don't see the difference between the 2 definitions you have proposed. Is it because the example I referred to attempted to make use of version control from the command line? If it is, then lets try to accomplish the same task via an .ado. file. Suppose I have the following prog def myado version 7.0 * perform sundry operations ... save myfile, old ... end If as you say, Stata provides the "ability of new versions of Stata to run do- and ado-files written with old syntax" then -myado- should behave the same way whether I invoke from Stata 7 or Stata 8. To me, this is an example of _backward_ compatibility, not forward. _Forward_ would mean the ability of older versions of Stata to mimic new versions of Stata and I never expected Stata to be able to accomplish that; backwards will suffice. Patrick Joly joly.patrick@ic.gc.ca pat.joly@utoronto.ca * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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