6.5.4 A pitfall

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There is a thing you should be aware of rather than learning the hard way.

If you translate combinations.lgs several times, you get the same result each time. Each time you translate it, it gets the same reference and the same date on the front page. That date indicates when the page was translated first time. The information about when the page was translated first time is encoded in Line 1 of combinations.lgs.

Now try to change something on the page like putting your own name in place of A.U.Thor, change the test case, or something. Adding a comment is not enough to count as a change.

Then, while you have combinations.lgs open in your favorite editor and while you view the page using your favorite web browser, retranslate the page:

   > lgs combinations

In the web browser you should see the date on the frontpage being updated to the current time as soon as you reload or whatever you do when you want to view changes.

More seriously (this is where the 'pitfall' comes in), combinations.lgs also changes. After recompilation, lgc(1) writes a new headline back to combinations.lgs. Note closely how your favorite editor reacted to that. My favorite editor (nedit) has this behavior: it notes the change, warns me, and asks if it should load the new version. If I say yes, nedit loads the new version and forgets its undo history. Learn what your favorite editor does and learn to live with it.

During development, I find it most convenient not to use headlines. You can avoid the headline in combinations.lgs just by deleting it. Lgc only writes back a headline if the file starts with "";;. You can get back the headline by adding "";; and recompile.

Headlines are only useful for pages that are included in distributions in source form.

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Copyright © 2010 Klaus Grue, GRD-2010-01-05