Category:CLP

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CLP is an acronym for Control Language Program.

Much of what we find in CLP programs are IBM Commands. [1] Also see CLP Coding Rules and Category:Commands.

As with many other languages, there are multiple versions in popular usage, such as CLP/400 and ILE-CLP.

In some realities, this is comparable to software that is the "glue" connecting higher level language programs like RPG; data base files and their over-rides; screen and print "files" and their over-rides; and other objects with Menus ... typically when we take a menu option, we are launching a CLP program.


CLP Unique Commands

Some 400 commands can ONLY be executed from within a CLP program, not from Command Line. In other programming languages, these might be called OP CODES.


In later releases, IBM also added the following CL-only commands (or "statements").


Special characters

Some characters have special meaning in CL:

Symbol Meaning
|| *CAT
|> *BCAT
|< *TCAT
= *EQ
> *GT
< *LT
>= *GE
<= *LE
¬= *NE
¬> *NG
¬< *NL
& *AND
| *OR
¬ *NOT

Ref: CL Programming, Expressions in CL commands


Built-in functions

Like RPG, CLP also supports many built-in functions. These would typically be used in CHGVAR and/or IF statements to manipulate variable data before its subsequent use. Initially, CLP offered the following built-in functions.

Function Use
 %BINary Convert signed decimal data to or from binary character format.
 %SubSTring Extract or set a subset of another character string.
 %SWITCH Evaluate one or more of the eight job switches and return a Boolean result.

As of V5R4 of the operating system, IBM added the following built-in functions to CLP.

Function Use
 %ADDRess Change or test the address stored in a CL pointer variable.
 %OFfSet Change or test the offset portion of an address stored in a CL pointer variable.

As of V7R1 of the operating system, IBM added the following built-in functions to CLP.

Function Use
 %CHECK Using a forward search, returns the first position in a base string that contains a character that is not in the comparator string — or zero if the base string contains only characters from the comparator string.
 %CHECKR Using a reverse search, returns the last position in a base string that contains a character that is not in the comparator string — or zero if the base string contains only characters from the comparator string.
 %SCAN Using a forward search, returns the first position of an argument string within a source string — or zero if not found.
 %TRIM Returns the supplied string with leading and trailing blank characters or argument characters removed.
 %TRIML Returns the supplied string with leading (i.e., leftmost) blank characters or argument characters removed.
 %TRIMR Returns the supplied string with trailing (i.e., rightmost) blank characters or argument characters removed.

As of V7R2 of the operating system, IBM added the following built-in functions to CLP.

Function Use
 %CHAR Converts logical, decimal, integer, or unsigned integer data to character format.
 %DEC Converts character, logical, decimal, integer, or unsigned integer data to packed decimal format.
 %INT Converts character, logical, decimal, or unsigned integer data to integer format.
 %LEN Returns the number of digits or characters of a CL numeric or character variable.
 %LOWER Returns a character string that is the same length as the argument specified with each uppercase letter replaced by the corresponding lowercase letter.
 %SIZE Returns the number of bytes occupied by the CL variable.
 %UINT Converts character, logical, decimal, or integer data to unsigned integer format.
 %UPPER Returns a character string that is the same length as the argument specified with each lowercase letter replaced by the corresponding uppercase letter.


Pointer use

As of V5R4, CL allows the use of pointers. There were some problems with uninitialised pointers, and PTFs were issued. As of 15 Feb 2008, 5722-SS1:

  • SI28620
  • SI28196
  • SI27953

These are immediate PTFs, but you will need to re-compile any CL programs using pointers in order to get the issues fixed.

One can't compare a pointer to *NULL, but a clever idea is to create an unused pointer (which will be set to *NULL if the above PTFs are applied) and compare to that. Here is a snippet from Tom L. for a CL program that performs getenv from a thread on RPG400-L. 

dcl &pNull *ptr  /* Auto-initialized to *null */
if ( &pEnvVar *eq &pNull )  do

Note: As of V6R1 of the operating system, complete *NULL support was added to ILE CL encompassing the DCL, IF, and CHGVAR statements.


Categories

Subcategories

This category has only the following subcategory.

C

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