ViGYAN's DESL

( TO) The DESL Global Options

There are several options which are termed global because they have the same meaning regardless of the command they are being applied to. Global options are applicable to all commands which allow options and which are entered in the command-line mode of input.

The current list of global options is :

alias
cancel
elsek
endifk
erase
go
ifk
options
quit
read/readn
reads/readsn
save
see
use/usen

Global options are not allowed within a section of input which is activated via the read- or use-type constructs.

If the read- or use-type construct needs to be used, the desired global options should to be entered prior to or after the read/use import of input lines.

Global options followed by their associated arguments should be the first and the only items on an input line unless specifically stated otherwise below.

The following is a summary of the global options. Following each global option is the syntax of any required or optional argument list.

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( TO1) alias To temporarily change the spelling of a option.
All original option spellings are restored after the execution of the current command. The alias structure has to be encountered before the first use of the changed option.
Syntax : alias newkw oldkw
where :
- newkw is the option's new spelling
- oldkw is the option's old spelling
Example : alias filez files ...
Aliasing is most useful when a option and a option argument would normally have had the same name.
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( TO2) cancel
To abort input, not process the current command, save all input in a save set and cause DESL to solicit a new command. (quit also aborts input but does not save the input thus far.)
Syntax : cancel
Note : cancel can appear anywhere before go
Example : cancel
Cancel can save you typing. If you realize, as you are typing input to a command, that you, for whatever reason, should not continue with the command, but would, nevertheless, like to salvage the input you have entered thus far, entering cancel will abort the command and save the input to a save set buffer, which you can later use as input to the same or another command.

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( TO21) elsek
Please see the documentation for the ifk option. It discusses the ifk, elsek, and endifk options.

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( TO22) endifk
Please see the documentation for the ifk option. It discusses the ifk, elsek, and endifk options.

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( TO3) erase
To remove the last one or more lines which have been entered as input for the current command.
Syntax : erase (#)
where :
# is an optional number of lines to erase. The default number is 1.
Example : erase 3
This can let you avoid having to use cancel. Just eliminate the most previous line(s) you just typed incorrectly and then continue entering input.

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( TO4) go
Signals the end of input for current command. After being encountered, the appropriate DESL function begins to execute if all input has been judged syntactically correct and sufficient.
Syntax : go
Note : go can appear anywhere on the input line
Example : go
When you enter this option plus a carriage return, it's all over but the shouting. DESL goes off and attempts to execute the command you have specified.

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( TO42) ifk
The DESL ifk global option is a special option which serves to logically determine whether a block of DESL command input will be used or not. It is a conditional option which is a part of a more complete ifk elsek endifk structure which can be included in any DESL command's input stream.
There can be up to 10 sets of conditional argument phrases associated with the ifk option. Each conditional phrase must be separated from the other by a conjunction.
If the conditions following ifk, considered altogether, accounting for ALL conjunctions and processing from left to right, are TRUE then any command input immediately following the ifk option, up to and including the input immediately preceding either the next elsek or endifk, or the end of input, whichever is encountered first, will be processed.
An ifk block CANNOT be nested within another ifk block.
After processing the pertinent section of command input, control jumps to the input immediately following the closing endif option.
If one or more of the conditions following the ifk, considered altogether, accounting for ALL conjunctions and processing from left to right, are FALSE then control jumps to the next elsek, or endifk option, whichever is encountered first. If an elsek command has been jumped to, the conditions included in this command are evaluated and processing continues as it did after the evaluation of the opening ifk statement. If an elsek option has been jumped to, any DESL input immediately following that elsek option, until the next endif option will be executed, after which control will jump to the input immediately following the closing endifk command.
Examples of two ifk else endifk structures which could be be contained in a command input file or macro is the following :
```
Example 1.
 

 print
  ifk *V1 eq 10 or *N2 eq run10
   files run9 run10 run11
  elsek
   files run9 run11
  endifk
  names alpha beta cl cd cm
  format g12.5 lines 999 go


Example 2.
 

 print
  ifk exists file run10 then
   files run9 run10 run11
  elsek
   files run9 run11
  endifk
  names alpha beta cl cd cm
  format g12.5 lines 999 go

 
 
```
There are two fundamental types of condition syntaxes which can be used :
1. ifk cond1 ( [and/or] cond2 ... [and/or] cond10 ) then
  where, "cond1", etc. represent "conditions".
2. ifk (not) exist(s) file(s) fn1 fn2 ... fni then
  where, "fn1", etc. represent file names
In Example 1, the first type of ifk option evaluates the True/False state of each condition, logically links them, from LEFT to RIGHT, via the expressed conjunction(s) and or or and determines an overall True/False state. For this type of if option up to ten (10) conditions can be specified.
In Example 2, the second type of ifk option involves checking to see if one or more files either are ALL in existence or are ALL NOT in existence. The resulting True/False state is set accordingly.
Then, for EITHER type of ifk command, based on this resulting state, the following block of input sections are processed or skipped.
The structure of a condition, used with the first type ifk option, (1) above, can be either of the following :
```
 .  [*N# ] [= ] [*N# ]    or   [*V#] [= ] [*V#]
 .  [str]  [eq] [str]          [##]  [eq] [##]
 .         [ne]                      [ne]
 .                                   [ge]
 .                                   [gt]
 .                                   [> ]
 .                                   [le]
 .                                   [lt]
 .                                   [< ]
 
```
where
- *N# and *V# represent the CONTENTS of register number #
- "str" represents ANY string other than *N# or *V#
- ## represents ANY value
- and "=", "eq", "ne", ... ,"<" are logical comparators with implicit meaning
A condition involves EITHER name-type OR value-type arguments
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( TO5) options/opt
To list the options which are permitted (required/optional) for the current command.
Syntax : options/opt
Example : optn

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( TO6) quit
To abort input, not process the current command, and cause DESL to solicit a new command. (cancel also aborts input and saves the input thus far.)
Syntax : quit
Note : quit can appear anywhere BEFORE go
Example : quit
If you get stuck or decide you just do not want to continue, enter quit plus a carriage return. You'll be back at the DESL> prompt ready to enter the same or a new command.

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( TO7) read/readn
To cause a group of lines to be read into the current command input sequence at the current location from an alternate file. Additionally, if read is specified and DESL is in the purely interactive mode a chance to edit the read-in file contents is given before the lines are inserted into the current input sequence. If DESL is not in the purely-interactive mode no chance to edit the read-in file will be given.
The file read into DESL via read or readn cannot, itself contain another form of the read option.
There should be no blank lines in a file to be accessed via read/readn.
If readn is specified, no chance to edit the read-in file will be given regardless of the current DESL mode.
Syntax : read(n) filename
where :
file_name is a required file name
Note : read(n) option phrase can appear anywhere on the line
Example : ... read fitinpt
Use the read(n) global option to avoid typing. One or more prepared input files can be referenced during the input to a DESL command.

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( TO8) reads/readsn
To cause a group of lines to be read into the current command input sequence at the current location from a named section on an alternate file. If reads is specified and DESL is in the purely interactive mode a chance to edit the read-in file section contents is given before the lines are inserted into the current input sequence.
The file read into DESL via read or readn cannot, itself contain another form of the read option.
There should be no blank lines in a file to be accessed via reads/readsn.
If readsn is specified, no chance to edit the read-in file section will be given regardless of the current DESL mode.
Syntax : reads(n) filename sectionname
where :
file_name is a required file name
section_name is a required section name
Note : "reads(n)" option phrase can appear anywhere on the line
Example : reads fitinpt sect1
Use the reads(n) global option to avoid typing. One or more prepared input file sections can be referenced during the input to a DESL command. A single input file can contain multiple individually-referenceable sections.
```
An example of a sectioned input file "fitinpt" :
                   .
                   .
                   .
              section sect1
                   .
                   .
                   .
               (any command input)
                   .
                   .
                   .
              section sect2
                   .
                   .
                   .
               (any command input)
                   .
                   .
                   .
```
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( TO10) save
To establish the name of the referenceable set of input which is currently being entered. (See "use(n)" for a description of how to read this type of saved input back in.) The default name of the input set is "save####", where #### is a unique 4-digit number.
Syntax : save savnam
where :
"savnam" is the desired name of the saved set of input
Note : "save" option group can appear anywhere on the line
Example : ... save savfit1 ...
All input, regardless of its origin, will be saved in a "save" buffer by SOME name unless "quit" is entered. This global option just lets you explicitly name the set rather than getting the default type name. Save sets ONLY exist within a DESL session : when the session ends the save sets in the internal buffer are gone. These "save" sets can, however, be moved out of the save buffer and copied to one or more files. The "saveinput" command provides this capability.

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( TO11) see
To allow a review of the existing referenceable sets of saved input.
Syntax : see ( save_set_name )
where :
"save_set_name" is an optional argument which can name the particular saved input set to review. If no saved set is named, all of the save-set names and the names of their originating commands will be displayed.
Example : see save0003
As a session proceeds, many "save" sets of input can be created. If you know that a while ago you entered a set of input which is almost like a set you need to enter again now, "see" provides the means for examining one or more of these sets, without using them, to find the one you may need to modify and reuse.

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( TO12) use/usen
To cause a group of lines to be read into the current command input sequence at the current location from a named or unnamed set of saved input. If "use" is specified, a chance to edit the named/unnamed saved set of input is given before the lines are inserted into the current input sequence. If "usen" is specified, no chance to edit the named/unnamed saved set of input is given before the lines are inserted into the current input sequence.
Syntax : use(n) ( save_set_name )
where :
save_set_name is an optional name of a previously created set of input.
If a save set is named the named save set is attempted to be accessed from the internal save buffer. If no save set is named the most recent set of input from the same command is searched for. If no save set from the same command is found, the most recent set from any command is used. If these are no save sets in existence, a reply from DESL to that effect will be made.
Note : "use(n)" option phrase can appear anywhere on the line
Example : usen save0003 ...
"use" provides the means to quickly "iterate" on an input set until the desired results are achieved. The "use" and "read" global options are similar : the "use" input comes from an internal buffer and the "read" input comes from a file.

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( TO) The DESL Global Options

© 1999 ViGYAN, Inc.