Why is it convention to have `(provide )` at the bottom of the file?

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I've been looking through some elisp libraries and most calls to provide happen at the end of the file. In clojure the ns is quite similar to provide.

I've noticed that putting provide at the top of the file makes no difference. Is there a reason for putting it at the end vs at the top?

provide

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edited 14 mins ago

Drew

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zcaudate

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• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  i'm talking about 'provide, not 'require
  – zcaudate
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
  – Basil
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
  – phils
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

favorite

I've been looking through some elisp libraries and most calls to provide happen at the end of the file. In clojure the ns is quite similar to provide.

I've noticed that putting provide at the top of the file makes no difference. Is there a reason for putting it at the end vs at the top?

provide

share|improve this question

edited 14 mins ago

Drew

45.1k460101

asked 2 hours ago

zcaudate

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  i'm talking about 'provide, not 'require
  – zcaudate
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
  – Basil
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
  – phils
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

favorite

up vote
1
down vote

favorite

I've been looking through some elisp libraries and most calls to provide happen at the end of the file. In clojure the ns is quite similar to provide.

I've noticed that putting provide at the top of the file makes no difference. Is there a reason for putting it at the end vs at the top?

provide

share|improve this question

edited 14 mins ago

Drew

45.1k460101

asked 2 hours ago

zcaudate

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

I've been looking through some elisp libraries and most calls to provide happen at the end of the file. In clojure the ns is quite similar to provide.

I've noticed that putting provide at the top of the file makes no difference. Is there a reason for putting it at the end vs at the top?

provide

provide

share|improve this question

edited 14 mins ago

Drew

45.1k460101

asked 2 hours ago

zcaudate

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 14 mins ago

Drew

45.1k460101

asked 2 hours ago

zcaudate

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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share|improve this question

share|improve this question

edited 14 mins ago

Drew

45.1k460101

edited 14 mins ago

Drew

45.1k460101

edited 14 mins ago

Drew

45.1k460101

45.1k460101

asked 2 hours ago

zcaudate

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 hours ago

zcaudate

1837

asked 2 hours ago

zcaudate

1837

1837

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

New contributor

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

zcaudate is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  i'm talking about 'provide, not 'require
  – zcaudate
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
  – Basil
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
  – phils
  1 hour ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
  – phils
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  i'm talking about 'provide, not 'require
  – zcaudate
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
  – Basil
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
  – phils
  1 hour ago
  

  
  
  
  

2

2

Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
– phils
1 hour ago

Possible duplicate of What does (require 'package) mean for emacs and how does it differ from load-file?
– phils
1 hour ago

1

1

or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
– phils
1 hour ago

or emacs.stackexchange.com/q/8288 or emacs.stackexchange.com/q/18638
– phils
1 hour ago

i'm talking about 'provide, not 'require
– zcaudate
1 hour ago

i'm talking about 'provide, not 'require
– zcaudate
1 hour ago

@zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
– Basil
1 hour ago

@zcaudate tl;dr it's part of how (elisp) Named Features are implemented.
– Basil
1 hour ago

1

1

Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
– phils
1 hour ago

Ah, so based on your edit you are not asking why libraries contain (provide <package>), but why they contain it at the bottom rather than at the top?
– phils
1 hour ago

add a comment | 

2 Answers
2

active

oldest

votes

up vote
2
down vote

The reason for putting the provide at the end rather than the beginning is the same as the reason for including the comment ;;; <library.el> ends here at the end of the file:

Because if it's not there, then you don't have the complete file.

The comment is the human-readable version of that, and (provide 'FEATURE) is the machine-readable version.

Imagine if you had a truncated copy of foo.el with (provide 'foo) at the top, and loading it caused errors -- but due to the provide Emacs believed it was now fully-loaded, and so subsequent (require 'foo) did nothing to fix the problem in that session, even after you installed a corrected copy of the file.

share|improve this answer

answered 1 hour ago

phils

24k23261

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
  – Basil
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

Because it's in the coding conventions, would be one answer. :)

The provide/require/features design is quite simple. When a package requires a feature it is loaded, but only if it isn't already loaded. That is determined by checking the list of features found in features.

Packages only add their features only once they have finished loading, i.e. only once their features become available to use. So, they do it last.

The value of the variable features stores the list. Mine currently has ~300 symbols in it.

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

add a comment | 

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2 Answers
2

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2 Answers
2

active

oldest

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oldest

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active

oldest

votes

up vote
2
down vote

The reason for putting the provide at the end rather than the beginning is the same as the reason for including the comment ;;; <library.el> ends here at the end of the file:

Because if it's not there, then you don't have the complete file.

The comment is the human-readable version of that, and (provide 'FEATURE) is the machine-readable version.

Imagine if you had a truncated copy of foo.el with (provide 'foo) at the top, and loading it caused errors -- but due to the provide Emacs believed it was now fully-loaded, and so subsequent (require 'foo) did nothing to fix the problem in that session, even after you installed a corrected copy of the file.

share|improve this answer

answered 1 hour ago

phils

24k23261

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
  – Basil
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

The reason for putting the provide at the end rather than the beginning is the same as the reason for including the comment ;;; <library.el> ends here at the end of the file:

Because if it's not there, then you don't have the complete file.

The comment is the human-readable version of that, and (provide 'FEATURE) is the machine-readable version.

Imagine if you had a truncated copy of foo.el with (provide 'foo) at the top, and loading it caused errors -- but due to the provide Emacs believed it was now fully-loaded, and so subsequent (require 'foo) did nothing to fix the problem in that session, even after you installed a corrected copy of the file.

share|improve this answer

answered 1 hour ago

phils

24k23261

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
  – Basil
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

up vote
2
down vote

The reason for putting the provide at the end rather than the beginning is the same as the reason for including the comment ;;; <library.el> ends here at the end of the file:

Because if it's not there, then you don't have the complete file.

The comment is the human-readable version of that, and (provide 'FEATURE) is the machine-readable version.

Imagine if you had a truncated copy of foo.el with (provide 'foo) at the top, and loading it caused errors -- but due to the provide Emacs believed it was now fully-loaded, and so subsequent (require 'foo) did nothing to fix the problem in that session, even after you installed a corrected copy of the file.

share|improve this answer

answered 1 hour ago

phils

24k23261

The reason for putting the provide at the end rather than the beginning is the same as the reason for including the comment ;;; <library.el> ends here at the end of the file:

Because if it's not there, then you don't have the complete file.

The comment is the human-readable version of that, and (provide 'FEATURE) is the machine-readable version.

Imagine if you had a truncated copy of foo.el with (provide 'foo) at the top, and loading it caused errors -- but due to the provide Emacs believed it was now fully-loaded, and so subsequent (require 'foo) did nothing to fix the problem in that session, even after you installed a corrected copy of the file.

share|improve this answer

answered 1 hour ago

phils

24k23261

share|improve this answer

share|improve this answer

answered 1 hour ago

phils

24k23261

answered 1 hour ago

phils

24k23261

answered 1 hour ago

phils

24k23261

24k23261

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
  – Basil
  1 hour ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
  – Basil
  1 hour ago
  

  
  
  
  

1

1

FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
– Basil
1 hour ago

FWIW, the purpose of the "ends here" heading is documented under (elisp) Library Headers.
– Basil
1 hour ago

add a comment | 

up vote
1
down vote

Because it's in the coding conventions, would be one answer. :)

The provide/require/features design is quite simple. When a package requires a feature it is loaded, but only if it isn't already loaded. That is determined by checking the list of features found in features.

Packages only add their features only once they have finished loading, i.e. only once their features become available to use. So, they do it last.

The value of the variable features stores the list. Mine currently has ~300 symbols in it.

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

add a comment | 

up vote
1
down vote

Because it's in the coding conventions, would be one answer. :)

The provide/require/features design is quite simple. When a package requires a feature it is loaded, but only if it isn't already loaded. That is determined by checking the list of features found in features.

Packages only add their features only once they have finished loading, i.e. only once their features become available to use. So, they do it last.

The value of the variable features stores the list. Mine currently has ~300 symbols in it.

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

add a comment | 

up vote
1
down vote

up vote
1
down vote

Because it's in the coding conventions, would be one answer. :)

The provide/require/features design is quite simple. When a package requires a feature it is loaded, but only if it isn't already loaded. That is determined by checking the list of features found in features.

Packages only add their features only once they have finished loading, i.e. only once their features become available to use. So, they do it last.

The value of the variable features stores the list. Mine currently has ~300 symbols in it.

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

Because it's in the coding conventions, would be one answer. :)

The provide/require/features design is quite simple. When a package requires a feature it is loaded, but only if it isn't already loaded. That is determined by checking the list of features found in features.

Packages only add their features only once they have finished loading, i.e. only once their features become available to use. So, they do it last.

The value of the variable features stores the list. Mine currently has ~300 symbols in it.

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

share|improve this answer

share|improve this answer

answered 1 hour ago

Ben Hyde

38629

answered 1 hour ago

Ben Hyde

38629

answered 1 hour ago

Ben Hyde

38629

38629

add a comment | 

add a comment | 

zcaudate is a new contributor. Be nice, and check out our Code of Conduct.

 

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