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4-1. WHILE COMMAND | |
4-2. PURPOSE | |
The WHILE command causes EDIT/3000 to repeat the two commands following subject to these conditions: While a WORK file condition specified in the EDIT/3000 command immediately following the WHILE
command can be met (the flag is true). Until the number of iterations specified by the SET TIME = limit command has been met (the default is 50 iterations). See Section III, paragraph 3-92 for a discussion of the SET command.
For example, the WHILE block
WHILE
FIND "EDIT/3000"
LIST *
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will cause EDIT/3000 to search forward in the WORK file from the current location of the pointer, find the string "EDIT/3000", and list the line containing the string. Once the line has been listed, the pointer is located at the first position of the next line and EDIT/3000 will search forward again for another occurrence of "EDIT/3000". When the end of the WORK file is reached, the condition specified in the first command (the flag command) will fail ("EDIT/3000" can no longer be located) and the WHILE block will terminate execution. (If the number of iterations specified in a SET command is reached before the end of the WORK file, execution
will terminate also.) If FLAG is used in the WHILE command, EDIT/3000 will repeat a single command (the command following
the WHILE command) until the flag is set to false or until the number of iterations allowed by the SET TIME
option in effect is reached. For example,
WHILE FLAG
FIND "EDIT/3000" (+8)
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will find the string "EDIT/3000", position the pointer to the last character in the string (number of characters in string -1) and search forward from there for another occurrence of the same string. When the end of the WORK file is reached, the flag will be set to false and the iterations will terminate. | | | |  | NOTE: The character position (+8) is necessary in the FIND command to position the
pointer to the last character in the string. Otherwise, EDIT/3000 would find
the string, the pointer would be located at the first character of the string, and
the next iteration would find the same string. In the above example, 1 can be
used instead of 8. | | | | |
4-3. FORM | |
The form of the WHILE command is 4-5. LIMITATIONS | |
In a WHILE block, a command may be a basic command or a set of basic commands preceded by a BEGIN command and terminated by an END command. (The BEGIN-END pair enclosing other commands comprises a compound command.) The commands in a WHILE block will execute only as long as the SET TIME = limit option in effect is not
exceeded, even if the flag remains true. The default limit is 50 iterations. (If the flag is set to false by EDIT/3000, of course, execution will terminate before the SET TIME value is reached.) The number of BEGIN-END pairs allowed in a WHILE block is determined by the SET DEPTH = limit command. The default limit is 10. If the SET SHORT command is used, display of WHILE block commands during execution is inhibited. If data is embedded in a WHILE block (using SET BATCH), it will be treated as if it were a command; slashes, numbers, and preceding blanks are removed. 4-6. EXAMPLES | |
Two examples of the WHILE command are provided. See paragraph 4-7,"BEGIN-END COMMAND," para-
graph 4-13, "NOT COMMAND," paragraph 4-19, "OR COMMAND," and paragraph 4-25, "YES COMMAND"
for examples of more complex WHILE blocks which use BEGIN-END pairs, and the NOT, OR, and YES
commands. The WORK file is shown below.
/S SHORT;T EDIT3;L ALL
1 1-2. WHAT IS EDIT/3000?
2
3 EDIT/3000 IS A SUBSYSTEM OF THE HP 3000
4 MULTI-POGRAMMING EXECUTIVE OPERATING SYSTEM
5 (MPE/3000) THAT IS USED TO CREATE AND
6 MANIPULATE ASCII FILES.
7
8 CHARACTERS, STRINGS OF CHARACTERS, 0R ENTIRE
9 LINES; OF CHARACTER CAN BE INSERTED, DELETED,
10 REPLACED, MODIFIED, SEARCHED FOR, AND OTHERWISE
11 MANIPULATED BY USING EDIT/3000 COMMANDS.
12
13 1-2. EDIT/3000 FEATURES
14
15 WITH EDIT/3000, IT IS POSSIBLE TO
16
17 CREATE AND BUILD A NEW FILE (CALLED A WORK FILE)
18 BY ENTERING COMMANDS AND LINES OF TEXT FROM THE
19 STANDARD INPUT DEVICE OR FROM A SPECIAL DISC FILE
20 CALLED THE HOLD FILE.
21
22 SAVE THE WORK FILE INTO A PERMANENT FILE CALLED
23 THE TEXT FILE.
24
25 CALL THE TEXT FILE BACK INTO THE WORK FILE FOR
26 FURTHER ADDITIONS AND/OR EDITING.
27
28 CHANGE ALL OCCURENCES OF A CHARACTER STRING WITH
29 ONE COMMAND.
30
31 DELETE CHARACTERS AND LINES FROM THE WORK FILE.
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In the following example, EDIT/3000 searches forward from the first position of the first line, finds the string "EDIT/3000" in line 1, and lists it. EDIT/3000 then searches forward again and finds and lists the string in lines 3, 11, 13, and 15. The string is not found again before the end of the WORK file is reached and the condition specified in the FIND "EDIT/3000" command fails. EDIT/3000 sets the flag false and prints the error message
*21* STRING NOT FOUND BEFORE LIMIT AT DEPTH 2
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Note that after the WHILE command is entered in a session, EDIT/3000 displays the / prompt character, then indents three positions for the next command. This is depth 2.
/FINDQ FIRST
/WHILE
/ FIND "EDIT/3000"
/ LIST*
/FIND "EDIT/3000"
1 1-2. WHAT IS EDIT/3000?
^ (15)
/LIST*
1 1-2. WHAT IS EDIT/3000?
/FIND "EDIT/3000"
3 EDIT/3000 IS A SUBSYSTEM OF THE HP 3000
^ (1 )
/LIST*
3 EDIT/3000 IS A SUBSYSTEM OF THE HP 3000
/FIND "EDIT/3000"
11 MANIPULATED BY USING EDIT/3000 COMMANDS.
^ (22 )
/LIST*
11 MANIPULATED BY USING EDIT/3000 COMMANDS.
/FIND "EDIT/3000"
13 1-2. EDIT/3000 FEATURES
^ (7 )
/LIST*
13 1-2. EDIT/3000 FEATURES
/FIND "EDIT/3000"
15 WITH EDIT/3000. IT IS POSSIBLE TO
^ (6 )
/LIST*
15 WITH EDIT/3000, IT IS POSSIBLE TO
/FIND "EDIT/3000"
*21*STRING NOT FOUND BEFORE LIMIT
AT DEPTH 2
-/LIST*
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The next example illustrates the use of the WHILE FLAG command. The WHILE FLAG command causes the
next command (instead of the next two commands) to be repeated until the condition specified in the command
fails and the flag is set to false by EDIT/3000. The command following WHILE FLAG (FIND "EDIT/3000"(+8)) searches forward, finds the string in line 1,
and lists it, The pointer is set to the last character of the string because of the (+8) character position
parameter. (To find the last character in a string, the character position parameter must be set equal to
number of characters in string &―;1.) The string is found and listed again in lines 3, 11, 13, and 15.
/FINDQ FIRST
/WHILE FLAG
/ FIND "EDIT/3000"(+8)
1 1-2. WHAT IS EDIT/3000?
^ (23 )
3 EDIT/3000 IS A SUBSYSTEM OF THE HP 3000
^ (9 )
11 MANIPULATED BY USING EDIT/3000 COMMANDS.
^ (30 )
13 1-2. EDIT/3000 FEATURES
^ (15 )
15 WITH EDIT/3000, IT IS POSSIBLE TO
^ (14 )
*21*STRING NOT FOUND BEFORE LIMIT
AT DEPTH 2
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The following example illustrates a FIND command in a WHILE block that does not use the character position parameter to position the pointer to the last character in the string being searched for. EDIT/3000 positions the pointer to the first character in the string. Thus, subsequent iterations of the FIND command locate the same occurrence of the string because the pointer location is not changed. The iterations were terminated by typing CONTROL Y.
/FINDQ FIRST
/WHILE FLAG
/ FIND "EDIT/3000"
/FIND "EDIT/3000"
1 1-2. WHAT IS EDIT/3000?
^ (15 )
/FIND "EDIT/3000"
1 1-2. WHAT IS EDIT/3000?
^ (15 )
/FIND "EDIT/3000"
1 1-2. WHAT IS EDIT/3000?
^ (15 )
/FIND "EDIT/3000"
1 1-2. WHAT IS EDIT/3000?
*21*STRING NOT FOUND BEFORE LIMIT
AT DEPTH 2
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