bug#3757: 23.0.95; can you explain why C-u make it appear not in minibuffer

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in 11.1.2 An Example: `print-elements-of-list' of `Instruction to
emacs lisp' , why C-u make the output not in minubuffer.
C-u is 4 by definition .
I can not understant why in the context.
can you explain more details or give some link ?
thanks
[email protected]



In GNU Emacs 23.0.95.1 (i686-pc-linux-gnu, GTK+ Version 2.14.7)
 of 2009-06-21 on laptop
Windowing system distributor `The X.Org Foundation', version 11.0.10503000
configured using `configure  '--prefix=/usr' '--build=i686-pc-linux-gnu'
'--host=i686-pc-linux-gnu' '--mandir=/usr/share/man'
'--infodir=/usr/share/info' '--datadir=/usr/share' '--sysconfdir=/etc'
'--localstatedir=/var/lib' '--program-suffix=-emacs-23'
'--infodir=/usr/share/info/emacs-23' '--with-sound' '--with-x'
'--without-toolkit-scroll-bars' '--with-gif' '--with-jpeg' '--with-png'
'--with-rsvg' '--with-tiff' '--with-xpm' '--with-xft' '--without-libotf'
'--without-m17n-flt' '--with-x-toolkit=gtk' '--without-hesiod'
'--without-kerberos' '--without-kerberos5' '--with-gpm' '--with-dbus'
'build_alias=i686-pc-linux-gnu' 'host_alias=i686-pc-linux-gnu' 'CFLAGS=-O2
-march=pentium-m -pipe' 'LDFLAGS=-Wl,-O1''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_US.UTF-8
  value of $LC_CTYPE: zh_CN.UTF-8
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=SCIM
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Info

Minor modes in effect:
  TeX-source-specials-mode: t
  minibuffer-depth-indicate-mode: t
  icicle-mode: t
  show-paren-mode: t
  display-time-mode: t
  global-auto-complete-mode: t
  desktop-save-mode: t
  yas/minor-mode: t
  auto-image-file-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
<double-mouse-5> <triple-down-mouse-5> <triple-mouse-5>
<down-mouse-5> <mouse-5> <double-down-mouse-5> <double-mouse-5>
<triple-down-mouse-5> <triple-mouse-5> <down-mouse-4>
<mouse-4> <down-mouse-4> <mouse-4> <down-mouse-4> <mouse-4>
<down-mouse-4> <mouse-4> <double-down-mouse-4> <double-mouse-4>
<help-echo> <help-echo> <menu-bar> <buffer> TAB <help-echo>
<tool-bar> <kill-buffer> <help-echo> <help-echo> <help-echo>
<menu-bar> <buffer> C-h <help-echo> <help-echo> <help-echo>
<tool-bar> <kill-buffer> <help-echo> <menu-bar> <buffer>
C-a <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <menu-bar> <buffer> C-a <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<down-mouse-5> <mouse-5> <double-down-mouse-5> <double-mouse-5>
<down-mouse-4> <mouse-4> <double-down-mouse-4> <double-mouse-4>
<down-mouse-4> <mouse-4> <down-mouse-4> <mouse-4> <down-mouse-4>
<mouse-4> <down-mouse-4> <mouse-4> <down-mouse-4> <mouse-4>
<down-mouse-4> <mouse-4> <double-down-mouse-4> <double-mouse-4>
<down-mouse-5> <mouse-5> <down-mouse-4> <mouse-4> <double-down-mouse-4>
<double-mouse-4> <down-mouse-5> <mouse-5> <down-mouse-5>
<mouse-5> <down-mouse-4> <mouse-4> <down-mouse-4> <mouse-4>
<down-mouse-4> <mouse-4> <down-mouse-5> <mouse-5> <double-down-mouse-5>
<double-mouse-5> <down-mouse-5> <mouse-5> <down-mouse-5>
<mouse-5> <double-down-mouse-5> <double-mouse-5> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4>
<triple-mouse-4> <triple-down-mouse-4> <triple-mouse-4>
<down-mouse-4> <mouse-4> <double-down-mouse-4> <double-mouse-4>
<triple-down-mouse-4> <triple-mouse-4> <down-mouse-4>
<mouse-4> <help-echo> <help-echo> <help-echo> <help-echo>
<down-mouse-5> <mouse-5> <down-mouse-5> <mouse-5> <help-echo>
<menu-bar> <buffer> C-a <help-echo> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4>
<triple-mouse-4> <down-mouse-5> <mouse-5> <double-down-mouse-5>
<double-mouse-5> <triple-down-mouse-5> <triple-mouse-5>
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5>
<triple-mouse-5> <down-mouse-4> <mouse-4> <double-down-mouse-4>
<double-mouse-4> <triple-down-mouse-4> <triple-mouse-4>
<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4>
<triple-mouse-4> <down-mouse-4> <mouse-4> <double-down-mouse-4>
<double-mouse-4> <down-mouse-4> <mouse-4> <double-down-mouse-4>
<double-mouse-4> <down-mouse-4> <mouse-4> <down-mouse-5>
<mouse-5> <double-down-mouse-5> <double-mouse-5> <triple-down-mouse-5>
<triple-mouse-5> <down-mouse-5> <mouse-5> <double-down-mouse-5>
<double-mouse-5> <triple-down-mouse-5> <triple-mouse-5>
<down-mouse-4> <mouse-4> <down-mouse-4> <mouse-4> <help-echo>
<menu-bar> <buffer> C-a <help-echo> <down-mouse-4>
<mouse-4> <down-mouse-4> <mouse-4> <down-mouse-5> <mouse-5>
<double-down-mouse-5> <double-mouse-5> <down-mouse-5>
<mouse-5> <down-mouse-1> <mouse-movement> <mouse-movement>
<drag-mouse-1> <down-mouse-1> <mouse-1> <down-mouse-1>
<mouse-movement> <mouse-movement> <drag-mouse-1> <help-echo>
<help-echo> <menu-bar> <buffer> C-b <down-mouse-1>
<mouse-movement> <mouse-movement> <help-echo> <drag-mouse-1>
<help-echo> <backspace> <down-mouse-1> <mouse-movement>
<mouse-movement> <mouse-movement> <mouse-movement>
<mouse-movement> <mouse-movement> <drag-mouse-1> \
<backspace> <down-mouse-1> <drag-mouse-1> <down-mouse-1>
<mouse-movement> <mouse-movement> <drag-mouse-1> <backspace>
<down-mouse-1> <mouse-1> C-x C-e <down-mouse-1> <mouse-movement>
<mouse-1> C-x C-e <down-mouse-1> <mouse-1> C-x C-e
C-u C-x C-e <menu-bar> <buffer> C-a <help-echo> <down-mouse-4>
<mouse-4> <down-mouse-5> <mouse-5> <down-mouse-4> <mouse-4>
<double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4>
<triple-mouse-4> <down-mouse-5> <mouse-5> <double-down-mouse-5>
<double-mouse-5> <down-mouse-5> <mouse-5> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4>
<triple-mouse-4> <triple-down-mouse-4> <triple-mouse-4>
<down-mouse-5> <mouse-5> <double-down-mouse-5> <double-mouse-5>
M-x r e p o r <tab> <return>

Recent messages:

gazelle

giraffe

lion

tiger
nil
Computing completion candidates...