problem of loading a package at emacs startup [duplicate]

Question

1. According to Emacs Eclim, I added the following to ~/.emacs.d/init.d for emacs-eclim:

   (require 'eclim)
   (global-eclim-mode)
   
   ; If you want to control eclimd from emacs, also add:
   (require 'eclimd)
   

   The output of emacs -nw --debug-init is:

   Debugger entered--Lisp error: (file-error "Cannot open load file" "eclim")
     require(eclim)
     eval-buffer(#<buffer  *load*> nil "/home/tim/.emacs.d/init.el" nil t)  ; Reading at buffer position 4117
     load-with-code-conversion("/home/tim/.emacs.d/init.el" "/home/tim/.emacs.d/init.el" t t)
     load("/home/tim/.emacs.d/init" t t)
     #[0 "^H\205\262^@     \306=\203^Q^@\307^H\310Q\202;^@ \311=\204^^^@\307^H\312Q\202;^@\313\307\314\315#\203*^@\316\202;^@\313\307\314\317#\$
     command-line()
     normal-top-level()
   

2. If I add the following line at the beginning:

   (add-to-list 'load-path "~/.emacs.d/elpa/emacs-eclim-20140809.207/")
   
   (require 'eclim)
   (global-eclim-mode)
   
   ; If you want to control eclimd from emacs, also add:
   (require 'eclimd)
   

   The output of emacs -nw --debug-init is:

   Debugger entered--Lisp error: (file-error "Cannot open load file" "s")
     require(s)
     byte-code("\300\301!\210\300\302!\210\303\304\305\306\307\310%\210\311\312\313\314\315\316\307\304&^G\207"
   [require etags s custom-declare$
     require(eclim)
     eval-buffer(#<buffer  *load*> nil "/home/tim/.emacs.d/init.el" nil t)  ; Reading at buffer position 4115
     load-with-code-conversion("/home/tim/.emacs.d/init.el" "/home/tim/.emacs.d/init.el" t t)
     load("/home/tim/.emacs.d/init" t t)
     #[0 "^H\205\262^@     \306=\203^Q^@\307^H\310Q\202;^@ \311=\204^^^@\307^H\312Q\202;^@\313\307\314\315#\203*^@\316\202;^@\313\307\314\317#\$
     command-line()
     normal-top-level()
   

3. If I instead add a different line at the beginning, it works without error:

   (package-initialize)
   
   (require 'eclim)
   (global-eclim-mode)
   
   ; If you want to control eclimd from emacs, also add:
   (require 'eclimd)
   

4. If I add both lines at the beginning, it also works:

   (add-to-list 'load-path "~/.emacs.d/elpa/emacs-eclim-20140809.207/")
   (package-initialize)
   
   (require 'eclim)
   (global-eclim-mode)
   
   ; If you want to control eclimd from emacs, also add:
   (require 'eclimd)
   

I wonder what the two lines I added do, and why they can work or not work? Thanks.

Answer 1

Your problem is that the package eclim as a dependency on the package s, so when you require eclim, you need to have s in your load-path. package-initialize ensure that every installed package are in you load-path, and load them too, so:

• you don't need to require eclim when you call package-initialize
• you need to add s to the load path if you don't call package-initialize

As you have installed those extension using package, better (and simpler) to use package-initialize.

Answer 2

It simply initializes all packages before running .emacs file. This way, you already have symbol eclim created, and you can use function "require" to require it. If you don't add package-initialize, then this package isn't initialized, eclim symbol is unbound, and you get situation that you had before :)