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I started a new question on this topic yesterday, and deleted it because I thought I had it solved. No, I'm still confused about exactly how require works. In my situation I have a file calctest.el in a path that load-path sees. Here is the simple file:

(defun calctest ()
  (calc-eval "deg(37@ 26' 36.42\")"))
(provide 'calctest)

Now, if I call (require 'calctest) in the scratch buffer, I get an error:

Required feature `calctest' was not provided". . .

This is even after a successful (load-library "calctest") and a test to see if it is loaded

(calctest) ==>
"37.44345"

But if I do a load-file on calctest.el, then do (require 'calctest) it "sees" it and "loads" it (again?). Why will a require not simply load my calctest? What am I missing here?

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But if I do a load-file on calctest.el, then do (require 'calctest) it "sees" it and "loads" it (again?).

No, the key point is that it doesn't load it.

When you load-file your calctest.el library, the (provide 'calctest) form is evaluated and remembered, which in turn satisfies any subsequent call to (require 'calctest) -- regardless of whether or not it would be able to load that library itself.

require is essentially just a load wrapper which avoids re-loading libraries -- it doesn't care (or even know) whether or not they were originally loaded by another call to require; just whether (provide 'FEATURE) has been evaluated at some point (in which case it loads nothing).

It very much sounds as if your calctest.el wasn't in your load-path when you were originally testing this.

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  • If I change a library after having done a require on it, I need it reloaded. How can I get require to redo it? Maybe see my similar question here. – 147pm Dec 7 '15 at 1:17
  • You can either call unload-feature first, or else simply load it with a non-require function. Personally I'd be disinclined to unload the feature in this instance unless I was testing the FEATURE-unload-function support. load-library or load-file are typically all I need when re-loading modified code. – phils Dec 7 '15 at 2:05
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Why will a require not simply load my calctest? What am I missing here?

Perhaps the path and a restart. require works only if the package is in the load-path. require also does some filename guessing based on the feature name. Restart Emacs may be required to trigger the re-loading.

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  • I'm probably doing something wrong, but what I don't know. Yes, now it appears to be working -- without needing loads of any sort. – 147pm Dec 6 '15 at 19:23

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