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Code Editor : jed011.html

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<h2 id="sec17" class="section">10&#X2003;Basic Editing</h2>
Editing with jed is pretty easy&#X2014; most keys simply insert themselves.
Movement around the buffer is usually done using the arrow keys or page up
and page down keys. If <code class="verb">edt.sl</code> is loaded, the keypads on VTxxx
terminals function as well. Here, only the highlights are touched upon
(cut/paste operations are not considered &#X201C;highlights&#X201D;). In the
following, any character prefixed by the <code class="verb">^</code> character denotes a
Control character. On keyboards without an explicit Escape key,
Ctrl-[ will most likely generate and Escape character.A &#X201C;prefix argument&#X201D; to a command may be generated by first hitting the
Esc key, then entering the number followed by pressing the desired
key. Normally, the prefix argument is used simply for repetition. For
example, to move to the right 40 characters, one would press
Esc 4 0 followed immediately by the right arrow key. This
illustrates the use of the repeat argument for repetition. However, the
prefix argument may be used in other ways as well. For example, to begin
defining a region, one would press the Ctrl-@ key. This sets the
mark and begins highlighting. Pressing the Ctrl-@ key with a prefix
argument will abort the act of defining the region and to pop the mark.The following list of useful keybindings assumes that <code class="verb">emacs.sl</code> has
been loaded.Ctrl-L 
 Redraw screen.Ctrl-_ 
 Undo (Control-underscore, also Ctrl-X u).Esc q 
 Reformat paragraph (wrap mode). Used with a prefix
argument. will justify the paragraph as well.Esc n 
 narrow paragraph (wrap mode). Used with a prefix
argument will justify the paragraph as well.Esc ; 
 Make Language comment (Fortran and C)Esc <code class="verb">\</code> 
 Trim whitespace around pointEsc ! 
 Execute shell commandEsc $ 
 Ispell word (unix)Ctrl-X ? 
 Show line/column information.&#X2018; 
 <code class="verb">quoted_insert</code> &#X2014; insert next char as is (backquote key)Esc s 
 Center line.Esc u 
 Upcase word.Esc d 
 Downcase word.Esc c 
 Capitalize word.Esc x 
 Get M-x minibuffer prompt with command completionCtrl-X Ctrl-B 
 pop up a list of buffersCtrl-X Ctrl-C 
 exit jedCtrl-X 0 
 Delete Current WindowCtrl-X 1 
 One Window.Ctrl-X 2 
 Split Window.Ctrl-X o 
 Other window.Ctrl-X b 
 switch to bufferCtrl-X k 
 kill bufferCtrl-X s 
 save some buffersCtrl-X Esc 
 Get S-Lang&gt; prompt for interface to the S-Lang
interpreter. Esc . 
 Find tag (unix ctags compatible)Ctrl-@ 
 Set Mark (Begin defining a region). Used with a
prefix argument aborts the act of defining the region and
pops the Mark.
<h3 id="sec18" class="subsection">10.1&#X2003;Undo</h3>
One of jed&#X2019;s nicest features is the ability to undo nearly any change
that occurs within a buffer at the touch of a key. If you delete a word,
you can undo it. If you delete 10 words in the middle of the buffer,
move to the top of the buffer and randomly make changes, you can undo all
of that too.By default, the <code class="verb">undo</code> function is bound to the key Ctrl-_
(Ascii 31). Since some terminals are not capable of generating this
character, it is also bound to the key sequence Ctrl-X u.Due to the lack of virtual memory support on IBMPC systems, the
<code class="verb">undo</code> function is not enabled on every buffer. In particular, it
is not enabled for the <code class="verb">*scratch*</code> buffer. However, it is enabled
for any buffer which is associated with a file. A &#X201C;plus&#X201D; character on
the left hand side of the status line indicates that undo is enabled for
the buffer. It is possible to enable undo for any buffer by using the
<code class="verb">toggle_undo</code> function.
<h3 id="sec19" class="subsection">10.2&#X2003;Marking Text (Point and Mark)</h3>
Many commands work on certain regions of text. A region is defined by
the <code class="verb">Point</code> and the <code class="verb">Mark</code> The <code class="verb">Point</code> is the location of
the current editing point or cursor position. The <code class="verb">Mark</code> is the
location of a mark. The mark is set using the <code class="verb">set_mark_cmd</code> which
is bound to Ctrl-@ (Control-2 or Control-Space on some keyboards).
When the mark is set, the m mark indicator will appear on the
status line. This indicates that a region is being defined. Moving the
cursor (<code class="verb">Point</code>) defines the other end of a region. If the variable
HIGHLIGHT is non-zero, jed will highlight the region as it is
defined.Even without highlighting, it is easy to see where the location of the mark
is by using the <code class="verb">exchange</code> command which is bound to Ctrl-X Ctrl-X.
This simply exchanges the <code class="verb">Point</code> and the <code class="verb">Mark</code>. The region is
still intact since it is defined only by the <code class="verb">Point</code> and <code class="verb">Mark</code>.
Pressing Ctrl-X Ctrl-X again restores the mark and Point back to their
original locations. Try it.
<h3 id="sec20" class="subsection">10.3&#X2003;Tab Issues.</h3>
Strictly speaking, jed uses only fixed column tabs whose size is
determined by the value of the <code class="verb">TAB</code> variable. Setting the <code class="verb">TAB</code>
variable to 0 causes jed to not use tabs as whitespace and to display
tabs as Ctrl-I. Please note that changing the tab settings on the
terminal will have no effect as far as jed is concerned. The
<code class="verb">TAB</code> variable is local to each buffer allowing every buffer to have
its own tab setting. The variable <code class="verb">TAB_DEFAULT</code> is the tab setting
that is given to all newly created buffers. The default value for this
variable is 8 which corresponds to eight column tabs.jed is also able to &#X201C;simulate&#X201D; arbitrary tabs as well through the use
of user defined tab stops. Calling the function <code class="verb">edit_tab_stops</code>
allows the user to interactively set the tab stops. That is, one simply
presses Esc X to get the <code class="verb">M-x</code> prompt and enters
<code class="verb">edit_tab_stops</code>. A window will pop open displaying the current tab
settings. To add a tab stop, simply place a T in the appropriate
column. Use the space bar to remove a tab stop.Here an argument is presented in favor of simulated tabs over real tab
stops. First, consider what a &#X201C;tab&#X201D; really is. A &#X201C;tab&#X201D; in a file is
nothing more than a character whose ASCII value is 9. For this reason,
one also denotes a tab as <code class="verb">^I</code> (Ctrl-I). Unlike most other
ASCII characters, the effect of the tab character is device dependent and
is controlled through the device tab settings. Hence, a file which
displays one way on one device may look totally different on another
device if the tab settings do not correspond. For this reason, many people
avoid tabs altogether and others the adopt &#X201C;standard&#X201D; of eight column
tabs. Even though people always argue about what the correct tab settings
should be, it must be kept in mind that this is primarily a human issue
and not a machine issue.On a device employing tab stops, a tab will cause the cursor to jump to
the position of the next tab stop. Now consider the effect of changing
the tab settings. Assume that in one part of a document, text was entered
using the first setting and in another part, the second setting was used.
When moving from the part of the document where the current tab setting is
appropriate to the part where the other tab setting was used will cause
the document to look unformatted unless the appropriate tab settings are
restored. Wordprocessors store the tab settings in the file with the text
so that the tabs may be dynamically changed to eliminate such unwanted
behavior. However, text editors such as jed, vi, Emacs, EDT, EVE (TPU),
etc, do not store this information in the file. jed avoids this problem
by using simulated tabs. When using simulated tabs, tabs are not really
used at all. Rather jed inserts the appropriate number of spaces to
achieve the desired effect. This also has the advantage of one being able
to cut and paste from the part of a document using one tab setting to
another part with a different tab setting. This simple operation may lead
to unwanted results on some wordprocessors as well as those text editors
using real tab stops.
<h3 id="sec21" class="subsection">10.4&#X2003;Searching</h3>
jed currently has two kinds of searches: ordinary searches and
incremental searches. Both types of searches have forward and backward
versions. The actual functions for binding purposes are:<pre class="verbatim"> search_forward
 search_backward
 isearch_forward
 isearch_backward
</pre>There is also the <code class="verb">occur</code> function which finds all occurrences of a
single word (string). This function has no backwards version. By default
it is not bound to any keys, so to use it, <code class="verb">occur</code> must be entered at
the <code class="verb">M-x</code> prompt (Esc X) or one is always free to bind it
to a key.In the following only the incremental search is discussed.The default type of search in Emacs in the incremental search. However,
since this type of search is confusing to the uninitiated, the ordinary
type of search has been made the default in jed&#X2019;s Emacs emulation. For the
traditional emacs keybinding, it is up to the user to provide the
keybinding.As the name suggests, an incremental search performs a search
incrementally. That is, as you enter the search string, the editor begins
searching right away. For example, suppose you wish to search for the
string apple. As soon as the letter a is entered into the
incremental search prompt, jed will search for the first occurrence of
a. Then as soon as the p is entered, jed will search from the
current point for the string ap, etc. This way, one is able to
quickly locate the desired string with only a minimal amount of
information.Unlike the &#X201C;ordinary&#X201D; search, the incremental search is not terminated
with the Enter key. Hitting the Enter key causes jed to
search for the next occurrence of the string based on the data currently
entered at the prompt. The search is terminated with the Esc key.Finally, the DEL key (Ctrl-?) is used to erase the last
character entered at the search prompt. In addition to erasing the last
character of the search string, jed will return back to the location of
the previous match. Erasing all characters will cause the editor to return
to the place where the search began. Like many things, this is one of
those that is easier to do than explain. Feel free to play around with
it.
<h3 id="sec22" class="subsection">10.5&#X2003;Rectangles</h3>
jed has built-in support for the editing of rectangular regions of
text. One corner of rectangle is defined by setting the mark somewhere in
the text. The Point (cursor location) defines the opposite corner of the
rectangle.Once a rectangle is defined, one may use the following functions:<code class="verb">kill_rect</code> 
 Delete text inside the rectangle saving the rectangle
in the internal rectangle buffer.<code class="verb">n_rect</code> 
 Push all text in the rectangle to the right outside the
rectangle.<code class="verb">copy_rect</code> 
 Copy text inside the rectangle to the internal rectangle
buffer.<code class="verb">blank_rect</code> 
 Replace all text inside the rectangle by spaces.The function <code class="verb">insert_rect</code> inserts a previously killed or copied
rectangle into the text at the Point.These functions have no default binding and must be entered into the
MiniBuffer by pressing Esc X to produce the <code class="verb">M-x</code> prompt.
<h3 id="sec23" class="subsection">10.6&#X2003;Sorting</h3>
jed is capable of sorting a region of lines using the heapsort
algorithm. The region is sorted alphabetically based upon the ASCII values
of the characters located within a user defined rectangle in the region.
That is, the rectangle simply defines the characters upon what the sort is
based. Simply move to the top line of the region and set the mark on the
top left corner of the rectangle. Move to the bottom line and place the
point at the position which defines the lower right corner of the
rectangle. Press Esc X to get the <code class="verb">M-x</code> prompt and enter
<code class="verb">sort</code> As as example, consider the following data:<pre class="verbatim"> Fruit: Quantity:
 lemons 3
 pears 37
 peaches 175
 apples 200
 oranges 56
</pre>To sort the data based upon the name, move the Point to the top left
corner of the sorting rectangle. In this case, the Point should be moved
to the l in the word lemons. Set the mark. Now move to the
lower right corner of the rectangle which is immediately after the s
in oranges. Pressing Esc X and entering <code class="verb">sort</code> yields:<pre class="verbatim"> Fruit: Quantity:
 apples 200
 lemons 3
 oranges 56
 peaches 175
 pears 37
</pre>Suppose that it is desired to sort by quantity instead. Looking at the
original (unsorted) data, move the Point to two spaces before the 3
on the line containing lemons. The cursor should be right under the
u in Quantity. Set the mark. Now move the Point to immediately after 56 on
the oranges line and again press Esc X and enter <code class="verb">sort</code>.
This yields the desired sort:<pre class="verbatim"> Fruit: Quantity:
 lemons 3
 pears 37
 oranges 56
 peaches 175
 apples 200
</pre>
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