--- rexxpub: defaults: rony.yaml logo: rexx --- . slide cover # Procedural and Object-oriented Programming 1 . subtitle **Statement, Routine (Procedure, Function), "Stem"-Variable** . cover-art . picture img/020_ooRexx_V08/p01-diagram-7.png . slide reference="Cf. rexxref.pdf (1.12.3. Labels)" # Labels - Identifier, followed by a colon (**:**) . click - Serves as a target for an internal routine - **CALL**-statements (invoking procedures) . click - Function invocations . click - **SIGNAL**-statements (like a "**GOTO**" instruction in other languages) . click - Exception handling (**SIGNAL ON** resp. **CALL ON**) . click ```rexx DO i = 1 TO 3 SAY "Oho!" i IF i = 1 THEN SIGNAL fin END fin : SAY "C'est la fin!" ``` . click label Output: . with ```output Oho! 1 C'est la fin! ``` # Internal Routines - Grouping of statements which repeatedly get executed by different parts in a program . click - Start with a label . click - Invocation . after - **CALL** label . after - Statements after the label get executed . after - The **RETURN**-statement returns control (to the statement immediately following the **CALL**-statement) . click - A „routine“ may also be called „procedure“ . slide reference="Cf. rexxref.pdf (7.2. Functions and Subroutines)" # Internal Routines ```rexx /* A Rexx-Programm with an internal routine named 'TIMESTAMP' */ CALL TimeStamp /* call a subroutine */ CALL SysSleep 5 /* sleep 5 seconds */ CALL TimeStamp /* call a subroutine */ EXIT /* exit program */ TimeStamp : /* label */ SAY "It is rather late ..." RETURN ``` . click label Output: . after numbered steps=0,1,2 each=after ```output It is rather late ... It is rather late ... ``` # Functions - Routines that return a value ("function value") to the caller via the ***RETURN***-statement . click - Invocation - Variant 1 - Invocation: the name (label), immediately followed by a left and right parenthesis - The return value ("function value") replaces the invocation . after ```rexx today = DATE() ``` . click - Variant 2 - Invocation: **CALL** followed by the name (label) of the routine - Interpreter stores the return value in the special variable **RESULT** . after ```rexx CALL DATE today = result ``` . slide reference="Cf. rexxref.pdf (2.3. CALL)" # Functions ```rexx /* A Rexx-Programm with an internal function named 'TIMESTAMP' */ SAY TimeStamp() /* function call */ CALL SysSleep 5 /* sleep 5 seconds */ CALL TimeStamp /* procedure call */ SAY result /* show function value */ EXIT /* exit program */ TimeStamp : /* label */ RETURN "It is rather late ..." ``` . click label Output: . after numbered steps=0,1,2 each=after ```output It is rather late ... It is rather late ... ``` . slide reference="Cf. rexxref.pdf (11.3.3. RC, 11.3.4. SIGL)" # Rexx Variables Used By Rexx - The Rexx interpreter may set the value of the following variables . after - **RESULT** - If a routine gets invoked with **CALL** and returns a value with its **RETURN** statement then the Rexx interpreter stores that returned value in a variable named **RESULT** . click - **RC** - Stores the "**r**eturn **c**ode" that the external command returned: a value of `0` (zero) indicates that the external command completed without any errors or failures . click - **SIGL** - Stores the line number which contains the **CALL** or **SIGNAL** statement that caused the jump to the routine ("**sig**nal **l**ine") . slide reference="Cf. rexxref.pdf (7.4. Built-in Functions (BIF))" # All Functions of REXX - Rexx provides the following built-in functions ("BIF"), some are specific to **strings** or **filenames**: . plain flow=5 - `ABBREV()`{style="color:#6b8e23"} - `ABS()` - `ADDRESS()` - `ARG()` - `B2X()` - `BEEP()` - `BITAND()` - `BITOR()` - `BITXOR()` - `C2D()` - `C2X()` - `CENTER()`{style="color:#6b8e23"} - `CHANGESTR()`{style="color:#6b8e23"} - `CHARIN()`{style="color:#c9211e"} - `CHAROUT()`{style="color:#c9211e"} - `CHARS()`{style="color:#c9211e"} - `COMPARE()` - `COPIES()`{style="color:#6b8e23"} - `COUNTSR()`{style="color:#6b8e23"} - `D2C()` - `D2X()` - `DATATYPE()` - `DATE()` - `DELSTR()`{style="color:#6b8e23"} - `DELWORD()`{style="color:#6b8e23"} - `DIGITS()` - `DIRECTORY()` - `ENDLOCAL()` - `ERRORTEXT()` - `FILESPEC()`{style="color:#c9211e"} - `FORM()` - `FORMAT()` - `FUZZ()` - `INSERT()`{style="color:#6b8e23"} - `LASTPOS()`{style="color:#6b8e23"} - `LEFT()`{style="color:#6b8e23"} - `LENGTH()`{style="color:#6b8e23"} - `LINEIN()`{style="color:#c9211e"} - `LINEOUT()`{style="color:#c9211e"} - `LINES()`{style="color:#c9211e"} - `MAX()` - `MIN()` - `OVERLAY()`{style="color:#6b8e23"} - `POS()`{style="color:#6b8e23"} - `QUEUED()` - `RANDOM()` - `REVERSE()`{style="color:#6b8e23"} - `RIGHT()`{style="color:#6b8e23"} - `SETLOCAL()` - `SIGN()` - `SOURCELINE()` - `SPACE()`{style="color:#6b8e23"} - `STREAM()`{style="color:#c9211e"} - `STRIP()`{style="color:#6b8e23"} - `SUBSTR()`{style="color:#6b8e23"} - `SUBWORD()`{style="color:#6b8e23"} - `SYMBOL()` - `TIME()` - `TRACE()` - `TRANSLATE()`{style="color:#6b8e23"} - `TRUNC()`{style="color:#6b8e23"} - `VALUE()` - `VAR()` - `VERIFY()`{style="color:#6b8e23"} - `WORD()`{style="color:#6b8e23"} - `WORDINDEX()`{style="color:#6b8e23"} - `WORDLENGTH()`{style="color:#6b8e23"} - `WORDPOS()`{style="color:#6b8e23"} - `WORDS()`{style="color:#6b8e23"} - `X2B()` - `X2C()` - `XRANGE()`{style="color:#6b8e23"} # External Rexx Function Packages - Standardised Interfaces to and from Rexx . click - Loading an external Rexx function package from Rexx, an example . after ```rexx IF RxFuncQuery("SysLoadFuncs") THEN DO CALL RxFuncAdd "SysLoadFuncs","RexxUtil","SysLoadFuncs" CALL SysLoadFuncs /* no quotes! */ END ``` . click - Function packages, which supply new functions to Rexx that are not part of the language, an example - Mark Hessling's "RexxSQL" – Direct access to the most important relational database management systems (DB2, Oracle, SQL-Server, MySQL, etc.) - https://sourceforge.net/projects/rexxsql/ . slide reference="Cf. rexxref.pdf (8. Rexx Utilities (RexxUtil))" # Function Package "RexxUtil" (Excerpt) - Contains more than 60 "useful" functions, some of which are only available for **Windows** or **Unix** operating systems. . plain flow=3 - `RxMessageBox`{style="color:#c9211e"} - `RxWinExec`{style="color:#c9211e"} - `SysAddRexxMacro` - `SysBootDrive`{style="color:#c9211e"} - `SysClearRexxMacroSpace` - `SysCls` - `SysCreatePipe`{style="color:#6b8e23"} - `SysCurPos`{style="color:#c9211e"} - `SysCurState`{style="color:#c9211e"} - `SysDriveInfo`{style="color:#c9211e"} - `SysDriveMap`{style="color:#c9211e"} - `SysDropRexxMacro` - `SysDumpVariables` - `SysFileCopy` - `SysFileDelete` - `SysFileExists` - `SysFileMove` - `SysFileSearch` - `SysFileSystemType`{style="color:#c9211e"} - `SysFileTree` - `SysFork`{style="color:#6b8e23"} - `SysFormatMessage` - `SysFromUnicode`{style="color:#c9211e"} - `SysGetErrorText` - `SysGetFileDateTime` - `SysGetKey` - `SysGetMessage`{style="color:#6b8e23"} - `SysGetMessageX`{style="color:#6b8e23"} - `SysGetShortPathName`{style="color:#c9211e"} - `SysIni`{style="color:#c9211e"} - `SysIsFile` - `SysIsFileCompressed`{style="color:#c9211e"} - `SysIsFileDirectory` - `SysIsFileEncrypted`{style="color:#c9211e"} - `SysIsFileLink` - `SysIsFileNotContentIndexed`{style="color:#c9211e"} - `SysIsFileOffline`{style="color:#c9211e"} - `SysIsFileSparse`{style="color:#c9211e"} - ... # Searching for Routines - Searching order for routines . plain steps level=1 | | | |---|---| | 1a) | Internal routines (in the program itself) | | 1b) | Routines defined as directives (in the program itself) | | 2) | The built-in Rexx routines ("built-in functions (BIF)") | | 3) | External routines (e.g. Rexx programs) | . click - It is possible to use the names of the language built-in functions . click - Overlay the respective routines . after - The overlayed built-in function can always be invoked by **enclosing its uppercased name in quotes**! # Searching for Routines ```rexx /* */ SAY date() /* invoke self programmed function below */ SAY "DATE"() /* invoke the Rexx built-in function */ EXIT DATE : /* "DATE" is in effect a Rexx function ! */ RETURN "Date(), self programmed!" ``` [Output (if run on 2059-05-20):]{.fragment} . after ```output Date(), self programmed! 20 May 2059 ``` . slide reference="Cf. rexxref.pdf (2.19. PROCEDURE)" # Scopes . steps . static - Define which variables and labels are seen in which part of a Rexx program - By default all variables in a program are globally visible/accessible, they belong to the **same scope** - Labels in a program are always global - If the keyword instruction **PROCEDURE** follows a label, then a new ("local") scope will be created for it - Should there be a need to access variables outside a local scope, then one must use the **EXPOSE** subkeyword of the **PROCEDURE**-Statement denoting those variable names. # Scopes ```rexx /* */ a = 1 b = 2 SAY "a=" a "b=" b CALL calc SAY "a=" a "b=" b EXIT calc : a = a * 2 b = b * 3 / 4 RETURN ``` [Output:]{.label .fragment anim=cut} . numbered steps=0,1,2 ```output a= 1 b= 2 a= 2 b= 1.5 ``` . slide reference="Cf. rexxref.pdf (2.19. PROCEDURE)" # Scopes ```rexx /* */ a = 1 b = 2 SAY "a=" a "b=" b CALL calc SAY "a=" a "b=" b EXIT calc: PROCEDURE /* no access to global "a" und "b" ! */ a = 5 /* hence, "a" must be defined locally */ b = 6 /* hence, "b" must be defined locally */ a = a * 2 b = b * 3 / 4 RETURN ``` . click label Output: . numbered steps=0,1,2 ```output a= 1 b= 2 a= 1 b= 2 ``` . slide reference="Cf. rexxref.pdf (2.19. PROCEDURE)" # Scopes ```rexx /* */ a = 1 b = 2 SAY "a=" a "b=" b CALL calc SAY "a=" a "b=" b EXIT calc: PROCEDURE EXPOSE b /* no access to "a", but to "b" ! */ a = 5 /* hence, "a" must be defined locally */ a = a * 2 b = b * 3 / 4 RETURN ``` . click label Output: . numbered steps=0,1,2 ```output a= 1 b= 2 a= 1 b= 1.5 ``` . slide reference="Cf. rexxref.pdf (1.13.4. Stems)" # "Stem" Variable (Associative Arrays) . after - Identifier contains one or more **dots** . click - The sequence of characters from the beginning up to and including the first dot is called **stem** (the remainder is called **tail**) . click ```rexx a.n = "aha" a.OnE = 1 a.1 = "Richard" Austria.Tyrol = 750000 Austria.Tyrol.Innsbruck = 135000 SAY a.1 a.n a.OnE SAY Austria.Tyrol ``` . click label Output: . after numbered steps=0,1,2 each=after ```output Richard aha 1 750000 ``` . slide reference="Cf. rexxref.pdf (1.13.4. Stems)" # "Stem" Variable (Associative Arrays) . after - Some RexxUtil functions (e.g. *SysFileTree()*) use a convention, which mandates that after the dot only integer numbers be used . click - **stem.0** – stores the total number of "elements"; this allows iterating over all stem entries starting with "**1**" going up to the number stored in **stem.0** . click ```rexx file.1 = "max.doc" file.2 = "moritz.doc" file.0 = 2 /* maximum number of "elements" */ DO i=1 TO file.0 SAY file.i /* "i" is also called "index" */ END ``` . click label Output: . after numbered steps=0,1,2 each=after ```output max.doc moritz.doc ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Blank - **PARSE** statements allow parsing a string and assigning (parts of it) to Rexx variables in one step . click ```rexx text = " Stiegler Seppl Stumm Zillertal/Tirol" PARSE VAR text famName firstName rest SAY famName SAY firstName SAY rest ``` . click label Output: . after numbered steps=0,1,2,3 each=after ```output Stiegler Seppl Stumm Zillertal/Tirol ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Blank ```rexx ruler = COPIES("1234+6789|", 5) text = " Stiegler Seppl Stumm Zillertal/Tirol" PARSE VAR text famName firstName rest SAY ruler; SAY text ; SAY SAY pp(famName); SAY pp(firstName) SAY pp(ruler); SAY pp(rest) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . with ```output 1234+6789|1234+6789|1234+6789|1234+6789|1234+6789| Stiegler Seppl Stumm Zillertal/Tirol [Stiegler] [Seppl] [1234+6789|1234+6789|1234+6789|1234+6789|1234+6789|] [ Stumm Zillertal/Tirol] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Blank ```rexx {blanks=all} ruler = COPIES("1234+6789|", 5) text = " Stiegler Seppl Stumm Zillertal/Tirol" PARSE VAR text famName firstName rest SAY ruler; SAY text ; SAY SAY pp(famName); SAY pp(firstName) SAY pp(ruler); SAY pp(rest) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . with ```output {blanks=all} 1234+6789|1234+6789|1234+6789|1234+6789|1234+6789| Stiegler Seppl Stumm Zillertal/Tirol [Stiegler] [Seppl] [1234+6789|1234+6789|1234+6789|1234+6789|1234+6789|] [ Stumm Zillertal/Tirol] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Pattern ```rexx /* 10 20 30 40 1234+6789|1234+6789|1234+6789|1234+6789| */ text = " Ruaniger Annelle Stumm Zillertal / Tirol " PARSE VAR text before "/" after SAY pp(before) SAY pp(after) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2 each=after ```output [ Ruaniger Annelle Stumm Zillertal ] [ Tirol ] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Pattern ```rexx pattern = "/" /* 10 20 30 40 1234+6789|1234+6789|1234+6789|1234+6789| */ text = " Ruaniger Annelle Stumm Zillertal / Tirol " PARSE VAR text before (pattern) after SAY pp(before) SAY pp(after) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2 each=after ```output [ Ruaniger Annelle Stumm Zillertal ] [ Tirol ] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Position, Length, Blank ```rexx /* 10 20 30 40 1234+6789|1234+6789|1234+6789|1234+6789| */ text = " Ruaniger Annelle Stumm Zillertal / Tirol " PARSE VAR text 3 famName +8 12 firstName city . SAY pp(famName) SAY pp(firstName) SAY pp(city) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2,3 each=after ```output [Ruaniger] [Annelle] [Stumm] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE by Value ```rexx text = "Sattler;Cilli;Stumm;Zillertal/Tirol" PARSE VAR text famName ";" firstName ";" city SAY pp(famName) SAY pp(firstName) SAY pp(city) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2,3 each=after ```output [Sattler] [Cilli] [Stumm;Zillertal/Tirol] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE Value Into Variable `a`{.rexx} and Use It for Parsing the Remainder ```rexx text = ";Sattler;Cilli;Stumm;Zillertal/Tirol" PARSE VAR text 1 a +1 famName (a) firstName (a) city (a) . SAY pp(famName) SAY pp(firstName) SAY pp(city) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2,3 each=after ```output [Sattler] [Cilli] [Stumm] ``` . slide reference="Cf. rexxref.pdf (9. Parsing)" kicker="PARSE #" # PARSE VALUE … WITH ... - **PARSE VALUE expression WITH pattern** . click - Makes it possible to immediately parse the result of an **expression** . after ```rexx PARSE VALUE date() WITH day month year say "year:" year "month:" month "day:" day ``` . click label Example: [**Output** (assuming **date()** returned the string `"20 May 2059"`)**:**]{.fragment} . click ```output year: 2059 month: May day: 20 ``` . slide reference="Cf. rexxref.pdf (2.18. PARSE)" kicker="PARSE #" # Input from Keyboard (“STDIN”) - **PARSE PULL** statements allow parsing a string read from the keyboard and assigning (parts of it) to Rexx variables in one step . click ```rexx SAY "1. What is your name?" /* Keyboard input: "Max" */ PARSE PULL name SAY "Your name is:" pp(name) SAY "2. What is your name?" /* Keyboard input: "moritz" */ PULL name SAY "Your name is:" pp(name) EXIT PP : RETURN "[" || ARG(1) || "]" -- "pretty print" ;) ``` . click label Output: . after numbered steps=0,1,2,3,4,5,6 each=after ```output 1. What is your name? Max Your name is: [Max] 2. What is your name? moritz Your name is: [MORITZ] ``` . slide reference="Cf. rexxref.pdf (2.18. PARSE)" kicker="PARSE #" # Retrieving Arguments PARSE ARG - **PARSE ARG** allows to fetch argument values . click ```rexx a = 1; b = 2 SAY "a=" a "b=" b CALL calc a , b SAY "a=" a "b=" b EXIT calc: PROCEDURE /* caller's variables "a" and "b" not visible ! */ PARSE ARG a , b /* fetch arguments and assign them to local variables */ SAY "calc: a=" a "b=" b a = a * 2 b = b * 3 / 4 SAY "calc: a=" a "b=" b RETURN ``` . click label Output: . numbered steps=0,1,2,3,4 ```output a= 1 b= 2 calc: a= 1 b= 2 calc: a= 2 b= 1.5 a= 1 b= 2 ``` . slide card logo=none # Contact