Books on REXX REXX Manuals Books on TSO TSO Manuals Tutorial: Comparison of CLIST language and REXX This will help you to convert CLIST to REXX. Literals. CLIST has no way of designating a literal and no consistent way of indicating that something is a variable. REXX, by contrast, has an excellent way of showing a literal: quotation marks or apostrophes. Variables are easily spotted in REXX's simply formed instructions. Variables. The ampersand (&) is used capriciously in CLISTs along with variables. Sometimes you use it; sometimes you don't. REXX makes it easy for you to show the difference between literals and variables, but forgives most lapses you might make. String manipulation. In order to manipulate strings of characters, you sometimes have to nest the &STR and &SUBSTR functions, which leads to very obscure coding. REXX is the queen of string manipulation. Its PARSE instruction and a multitude of functions make it easy to do anything you want with character data. Mathematics. CLIST does not take mathematics very seriously and should be used only for the simplest of calculations. CLIST may be adequate for calculating JCL SPACE requirements but for little else. REXX can do enough arithmetic to please almost anyone. Those who really like trigonometric functions and fractional exponents will probably forgive REXX for not having them when they see that REXX can do arithmetic to any precision. Control structures. CLIST now has adequate control structures, but one still finds many confusing programs that date back to the time when CLIST's control structures were poor. I feel sorrow and pity for the archaeologists in the twenty-third century who will spend innumerable days and nights poring over ancient CLISTs trying to fathom their meaning. Control structures and REXX grew up together. REXX fulfills every programmer's dreams about control structures. Rat's nest programs are possible in REXX, but REXX's designer took steps to penalize anyone who would abuse structured programming concepts.   Clarity. CLIST programs often tax the poor programmer's analytical capabilities as he or she tries to understand how CLIST attempts to interpret data strings as expressions and then tries valiantly to prevent it from doing so. CLIST language is the incarnation of obscurity. REXX does not think data is to be analyzed. It contents itself with analyzing verbs, variables, literals, functions, and labels, but not, thank you, REXX, data! Usefulness.The CLIST language is like nothing else in the entire spectrum of programming languages. REXX is becoming a kind of Esperanto, or universal language, in the programming world. It looks a lot like BASIC, PLI (especially) and C (a little. Nothing else really looks like C!). I have used REXX in IBM's VM/CMS programming system, in OS/2, and in PC-DOS, and have found that it is the same in each environment. REXX is your key to other IBM programming environments. Here in tabular form are the major differences between CLIST and REXX:   CLIST REXX Old New Bad for data strings Good string handling Lots of &&&&& English-like Obscure at times Clear Good control structures Excellent control structures Bad for math Good for math Few useful functions Many good functions Unique Common Prompts for positional parms No prompting for positional parms Execution Differences CLISTs are generally contained in libraries (PDSs) whose names end in ".CLIST." (.CLIST not required, but recommended) TSO is informed of the library by means of the TSO command ALLOCATE, which specifies the name of the library and the DDNAME (data definition name, abbreviated DDN) SYSPROC. The ALLOCATE command is done like this: ALLOC DDN(SYSPROC) SHR REUSE DSN(MYPROGS.CLIST) An ALTLIB command may also be done: ALTLIB ACTIVATE APPL(CLIST) DA(MYPROGS.CLIST)   REXX programs are generally contained in libraries (PDSs) whose names end in ".EXEC." (.EXEC not required, but recommended) TSO is informed of the library by means of the TSO command ALLOCATE, which specifies the name of the library and the DDNAME (data definition name, abbreviated DDN) SYSEXEC. The ALLOCATE command is done like this: ALLOC DDN(SYSEXEC) SHR REUSE DSN(MYPROGS.EXEC) An ALTLIB command may also be done: ALTLIB ACTIVATE APPL(EXEC) DA(MYPROGS.EXEC) REXX programs may be in the same libraries as CLISTs. If you do that, please start your REXX program with the comment shown just below. An explanation of when you need the comment and when you don't, is beyond the scope of this short paper /*REXX */ ARG USERID "SEND 'HELLO' USER("USERID")"   Corresponding Features in CLIST and REXX   Conversion of one language to another requires a knowledge of both languages and how they function. CLISTs and REXX share many features. Both have good control structures such as DO WHILE. These can usually be converted without any problem. However, CLIST GOTOs cannot always be converted to REXX SIGNALs, because the latter destroy any loop or control structure they are in. You may have to rewrite the logic of CLIST GOTOs. Changing the value of a loop variable in REXX affects the outcome of the loop. An example of this is DO I = 1 to 10 and changing the value of I within the loop. CLIST does not function the same way. REXX has nothing even near GLOBAL variables. You can use ISPF Variable Services to produce the same results. CLIST examines a program statement and processes it repeatedly until all "&" variables are resolved. REXX examines a statement once only, unless you use the INTERPRET instruction. CLIST statements containing variables within variables may severely tax your conversion abilities. The CLIST PROC statement works differently from REXX ARG. There is no one-to-one correspondence. You will have to execute REXX differently without reliance on keyword parameters. REXX has no WRITENR which displays a message and leaves the cursor at the end of the line. You might consider using ISPF panels, although this is considerably more involved.     CLIST Features REXX Equivalents AND & IF &A = 1 AND &B = 2 IF A = 1 & B = 2 ATTN HALT trap ATTN DO SIGNAL ON HALT ... END CLOSFILE EXECIO with FINIS option Concatenation by juxtaposition Concatenation by juxtaposition All spaces remain. > 1 spaces become 1 space WRITE HI NICE DAY! SAY HI NICE DAY! -> HI NICE DAY! -> HI NICE DAY! Concatenation with operator Concatenation with operator SET &NAME = WILL ¦ FRED NAME = "WILL" ¦ "FRED" CONTROL LIST TRACE C CONTROL NOMSG CALL MSG "OFF" CONTROL PROMPT CALL PROMPT "ON" CONTROL SYMLIST CONLIST TRACE I DATA Environment commands in quotes LISTCAT "LISTCAT" LISTDS "LISTDS" ENDDATA &DATATYPE DATATYPE function IF &DATATYPE(&NUM1) = NUM IF DATATYPE(NUM1) = "NUM" DO WHILE DO WHILE Error trap ERROR, SYNTAX traps ERROR DO SIGNAL ON ERROR ... SIGNAL ON SYNTAX END &EVAL No equivalent EXIT CODE(number EXIT number EXIT CODE(10) EXIT 10 EXIT QUIT No equivalent File IO EXECIO GETFILE INFILE EXECIO 1 DISKR INFILE GLOBAL variables No equivalent GLOBAL &V1 &V2 &V3 IF ... AND IF ... & IF ... OR IF ... ¦ IF (null IF ... NOP GOTO SIGNAL label GOTO ENDPROG SIGNAL ENDPROG &LASTCC and &MAXCC RC set after all instructions set after environment commands &LENGTH LENGTH function &LENGTH(ABCD) LENGTH("ABCD") LISTDSI dsn CALL LISTDSI "dsn" Literal has no delimiter, Literal uses " or ', or no delimiter or uses &STR() SAY "HELLO" WRITE HELLO &MAXCC RC set after all instructions set after environment commands NGLOBAL No equivalent NGLOBAL VAR1 &NRSTR No equivalent OPENFILE EXECIO PROC No equivalent keyword parameters with default PROC 0 TRACE(NO) PROC No equivalent keyword parameters without default PROC 0 TRACE PROC prompts for positionals ARG does not prompt PROC 1 VAR1 ARG VAR1 PROC statement ARG (approximate) PROC 1 VAR1 ARG VAR1 PUTFILE EXECIO DISKW READ &var PULL (approximate) READ &NAME PULL NAME READ (goes into &SYSDVAL) No equivalent RETURN RETURN (approximate) SELECT SELECT subroutine label subroutine label: SUBR: PROC 1 VAR1 SUBR: ARG VAR1 subroutine END subroutine RETURN subroutine SYSREF subroutine EXPOSE (approximate) SYSREF VAR1 EXPOSE VAR1 &SUBSTR SUBSTR function WRITE &SUBSTR(1:3,ABC) SAY SUBSTR("ABC",1,3) &STR No exact equivalent. Consider literal delimiters &SYSASIS No exact equivalent. Consider PARSE [UPPER] SYSCALL CALL SYSCALL SUBROUT CALL SUBROUT &SYSCAPS PARSE UPPER &SYSCPU SYSVAR(SYSCPU) function &SYSDATE, &SYSTIME DATE function WRITE &SYSDATE SAY DATE() &SYSDLM No equivalent &SYSDSN SYSDSN function &SYSDVAL No equivalent &SYSENV SYSVAR(SYSENV) function &SYSFLUSH No equivalent &SYSHSM SYSVAR(SYSHSM) function &SYSICMD No equivalent (but see PARSE SOURCE) &SYSINDEX INDEX function &SYSISPF SYSVAR(SYSISPF) function &SYSLC No equivalent &SYSJDATE DATE("J") function &SYSLTERM SYSVAR(SYSLTERM) function &SYSLRACF SYSVAR(SYSLRACF) function &SYSNEST SYSVAR(SYSNEST) function &SYSNSUB No equivalent &SYSOUTLINE OUTTRAP function SET &LINE = &&SYSOUTLINE&ctr LINE = LINE.I (in loop varying I) &SYSOUTTRAP OUTTRAP function SET &SYSOUTTRAP = 200 CALL OUTTRAP "LINE.", 200 SET &SYSOUTTRAP = 0 CALL OUTTRAP "OFF" &SYSPCMD No equivalent &SYSPREF SYSVAR(SYSPREF) function &SYSPROC SYSVAR(SYSPROC) function WRITE THE PROC = SAY "THE PROC = " WRITE &SYSPROC SAY SYSVAR(SYSPROC) &SYSRACF SYSVAR(SYSRACF) function &SYSSCAN No equivalent &SYSSCMD No equivalent &SYSSDATE DATE("S") function &SYSSRV SYSVAR(SYSSRV) function &SYSSTIME TIME() function &SYSTIME TIME() function &SYSTSOE SYSVAR(SYSTSOE) function &SYSUID USERID() function WRITE YOU ARE &SYSUID SAY "YOU ARE " USERID() &SYSWTERM LINESIZE function or SYSVAR(SYSWTERM) function TERMIN No equivalent Variable starts with & Variable starts no special way WRITE &NAME SAY NAME WRITE SAY WRITE PLEASE ENTER NAME SAY "PLEASE ENTER NAME" WRITENR No exact equivalent + - continuation continuation with "," WRITE PLEASE ENTER + SAY "PLEASE ENTER", NAME "NAME" The IBM Manual on REXX/CLIST Top of Page