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Assignments and Symbols
A variable is an object whose value can change during the running of a REXX program. The process of
changing the value of a variable is called assigning a new value to it. The value of a variable is a single
character string, of any length, that may contain any characters.
You can assign a new value to a variable with the ARG, PARSE, or PULL instructions, the VALUE built-in
function, or the variable pool interface, but the most common way of changing the value of a variable is
the assignment instruction itself. Any clause of the form:
symbol=expression;
is taken to be an assignment. The result of expression becomes the new value of the variable named by
the symbol to the left of the equal sign. Currently, on VM if you omit expression, the variable is set to the
null string. However, it is recommended that you explicitly set a variable to the null string: symbol=''.
Example:
/* Next line gives FRED the value "Frederic" */
Fred='Frederic'
The symbol naming the variable cannot begin with a digit (0–9) or a period. (Without this restriction on the
first character of a variable name, you could redefine a number; for example 3=4; would give a variable
called 3 the value 4.)
You can use a symbol in an expression even if you have not assigned it a value, because a symbol has a
defined value at all times. A variable you have not assigned a value is uninitialized. Its value is the
characters of the symbol itself, translated to uppercase (that is, lowercase a–z to uppercase A–Z).
However, if it is a compound symbol (described under section “Compound Symbols” on page 122), its
value is the derived name of the symbol.
Example:
/* If Freda has not yet been assigned a value, */
/* then next line gives FRED the value "FREDA" */
Fred=Freda
The meaning of a symbol in REXX varies according to its context. As a term in an expression (rather than
a keyword of some kind, for example), a symbol belongs to one of four groups: constant symbols, simple
symbols, compound symbols, and stems. Constant symbols cannot be assigned new values. You can use
simple symbols for variables where the name corresponds to a single value. You can use compound
symbols and stems for more complex collections of variables, such as arrays and lists.
Constant Symbols
A constant symbol starts with a digit (0–9) or a period.
You cannot change the value of a constant symbol. It is simply the string consisting of the characters of
the symbol (that is, with any lowercase alphabetic characters translated to uppercase).
These are constant symbols:
77
827.53
.12345
12e5 /* Same as 12E5 */
3D
17E-3
REXX General Concepts
Chapter 12. REXX General Concepts 121
- R EXX Guide 1
- Contents 5
- Contents v 7
- Contents vii 9
- Contents ix 11
- Contents xi 13
- Contents xiii 15
- Contents xv 17
- Contents xvii 19
- What this book is about 21
- Who this book is for 21
- Prerequisites 21
- Part 1. User's Guide 23
- Chapter 1. Introduction 25
- Components of REXX 26
- What is a REXX Program? 27
- Syntax of REXX Instructions 28
- Ending an instruction 29
- Continuing an instruction 29
- Types of REXX Clauses 31
- Null Clause 32
- Typing in a Program 33
- Running a Program 33
- Interpreting Error Messages 34
- Characters within a program 35
- Characters Input to a program 36
- Specifying Too Few Values 37
- Specifying Too Many Values 37
- Passing Arguments 39
- Program Variables 41
- Using Variables 41
- Variable Names 41
- Variable Values 42
- Using Expressions 43
- Order of Evaluation 44
- Comparison Operators 45
- Using Comparison Expressions 46
- Logical (Boolean) Operators 47
- Using Logical Expressions 48
- Concatenation Operators 49
- Priority of Operators 50
- Tracing Operations 51
- Tracing Results 52
- IF...THEN...ELSE Instructions 55
- Control Flow within a Program 56
- Tr ueFalse 58
- Using Looping Instructions 61
- Repetitive Loops 61
- Infinite Loops 62
- DO FOREVER Loops 62
- LEAVE Instruction 63
- ITERATE Instruction 63
- Conditional Loops 64
- DO WHILE 65
- DO UNTIL 66
- Combining Types of Loops 68
- Nested DO Loops 68
- Exercises - Combining Loops 69
- Using Interrupt Instructions 70
- EXIT Instruction 70
- CALL and RETURN Instructions 71
- SIGNAL Instruction 72
- Chapter 5. Using Functions 73
- Built-In Functions 74
- Arithmetic Functions 75
- Comparison Functions 75
- Conversion Functions 75
- Formatting Functions 76
- String Manipulating Functions 76
- Miscellaneous Functions 77
- Using Functions 78
- Passing Information 82
- ARG arg1, arg2, arg3, 87
- Exercise - Writing a Function 90
- Chapter 7. Manipulating Data 93
- Using Stems 94
- Parsing Data 95
- Parsing Instructions 95
- ARG Instruction 96
- PARSE VAR Instruction 96
- More about Parsing into Words 97
- Parsing with Patterns 97
- Variable 98
- Manipulating Data 100
- Types of Commands 103
- Using Variables in Commands 103
- Using Commands from a Program 104
- Debugging Programs 107
- Starting Interactive Debug 108
- Ending Interactive Debug 109
- Consider the Data 111
- Test Yourself 111
- Happy Hour 112
- Designing a Program 114
- Methods for Designing Loops 115
- The Conclusion 115
- What Do We Have So Far? 116
- Reconsider the Data 117
- Correcting Your Program 117
- Modifying Your Program 117
- Tracing Your Program 117
- Coding Style 118
- Part 2. Reference 123
- Chapter 11. Introduction 125
- Introduction 126
- SQL Interface 128
- Structure and General Syntax 131
- Characters 132
- Comments 132
- REXX General Concepts 133
- Implied Semicolons 136
- Continuations 137
- Expressions and Operators 137
- Expressions 137
- Operators 137
- String Concatenation 138
- Arithmetic 138
- Comparison 139
- Logical (Boolean) 140
- Assignments and Symbols 143
- Constant Symbols 143
- Simple Symbols 144
- Compound Symbols 144
- Environment 146
- Commands 146
- REXX Exec Invocation 147
- Where Execs Execute 148
- Locating and Loading Execs 148
- Editing Execs 148
- DBCS Support 151
- Miscellaneous Features 151
- ADDRESS VALUE expression 153
- Simple DO Group 160
- Repetitive DO Loops 161
- INTERPRET 167
- OPTIONS expression ; 173
- Parse Numeric Var1 175
- PARSE VAR string word1 string 175
- PROCEDURE 177
- RETURN 183
- Example: 184
- Prefix Options 189
- Numeric Options 190
- A Typical Example 190
- Format of TRACE Output 190
- Chapter 14. Functions 193
- Search Order 194
- Errors During Execution 195
- Built-in Functions 196
- ABBREV (Abbreviation) 197
- ABS (Absolute Value) 197
- ARG (Argument) 197
- BITAND (Bit by Bit AND) 198
- BITOR (Bit by Bit OR) 199
- B2X (Binary to Hexadecimal) 199
- CENTER/CENTRE 200
- CONDITION 200
- C2D (Character to Decimal) 201
- DATATYPE 202
- Functions 203
- DELSTR (Delete String) 205
- DELWORD (Delete Word) 205
- D2C (Decimal to Character) 205
- D2X (Decimal to Hexadecimal) 206
- ERRORTEXT 206
- EXTERNALS 207
- LASTPOS (Last Position) 210
- LINESIZE 210
- MAX (Maximum) 210
- MIN (Minimum) 211
- POS (Position) 211
- SOURCELINE 213
- SUBSTR (Substring) 214
- TRANSLATE 217
- TRUNC (Truncate) 217
- WORDINDEX 220
- WORDLENGTH 220
- WORDPOS (Word Position) 220
- XRANGE (Hexadecimal Range) 220
- X2B (Hexadecimal to Binary) 221
- X2D (Hexadecimal to Decimal) 221
- Chapter 15. Parsing 225
- The Period as a Placeholder 226
- Chapter 15. Parsing 205 227
- Chapter 15. Parsing 207 229
- Using UPPER 231
- Parsing Instructions Summary 232
- Parsing Instructions Examples 232
- Advanced Topics in Parsing 233
- Parsing Multiple Strings 233
- Parsing with DBCS Characters 235
- Details of Steps in Parsing 235
- Chapter 15. Parsing 215 237
- Definition 240
- Precision 240
- Arithmetic Operators 240
- Addition and Subtraction 241
- Multiplication 241
- Division 242
- Basic Operator Examples 242
- Integer Division 243
- Remainder 243
- Additional Operator Examples 243
- Numeric Comparisons 244
- Exponential Notation 244
- Numbers and Arithmetic 245
- Numeric Information 246
- Whole Numbers 246
- Numbers Used Directly by REXX 246
- Condition Information 250
- Descriptive Strings 250
- Special Variables 250
- The Special Variable RC 250
- The Special Variable SIGL 250
- Invocation 253
- Screen Format 254
- Prefix Commands 254
- Individual Line Commands 254
- Consecutive Block Commands 255
- Destination Commands 255
- Command Line Commands 256
- BACKWARD 257
- Text Editor 258
- Return Codes 260
- Operands 260
- RESERVED 273
- POOL1:\USERS\USER1\TEST.EXEC 279
- Current Directory and Path 280
- Security 281
- RFS commands 281
- File System 282
- File List Utility 286
- FLST Commands 287
- FLST Return Codes 294
- Directories and Lists 295
- RLS commands 297
- List System 298
- Background 303
- Highlights 303
- Command Definition 304
- CICPARMS Control Block 305
- Non-REXX Language Interfaces 306
- Programming Considerations 307
- Embedding SQL Statements 307
- DB2 Interface 308
- Receiving the Results 309
- Example Using SQL Statements 310
- Overview 313
- REXX/CICS Client Exec Example 314
- REXX/CICS Server Exec Example 315
- Facility 317
- Example of Panel Definition 317
- Defining Panels 318
- Panel Facility 319
- PANEL RUNTIME 324
- PANEL Variables 327
- System Error Reason Codes 329
- State Codes and Input Codes 330
- State codes 331
- Input codes 331
- Location Codes 332
- Examples of Sample Panels 332
- Example 1 332
- Example 2 333
- Example 3 333
- Example 4 334
- Example 5 334
- AUTHUSER 342
- Examples 343
- CONVTMAP 348
- DEFTRNID 360
- EXECDROP 364
- EXECLOAD 368
- FILEPOOL 372
- LISTCLIB 379
- LISTELIB 380
- LISTPOOL 381
- LISTTRNID 382
- SCRNINFO 390
- WAITREAD 397
- Part 3. Appendixes 399
- Error Numbers and Messages 402
- Appendix B. Return Codes 409
- LISTCLIB and LISTELIB 413
- General Description 417
- Symbols and Strings 418
- Validation 419
- Instruction Examples 419
- PUSH and QUEUE 420
- SAY and TRACE 420
- DBCS Function Handling 421
- Built-in Function Examples 422
- DBCS Processing Functions 426
- Counting Option 426
- Function Descriptions 426
- DBADJUST 426
- DBBRACKET 426
- DBCENTER 427
- DBCJUSTIFY 427
- DBRRIGHT 428
- DBTODBCS 429
- DBTOSBCS 429
- DBUNBRACKET 429
- DBVALIDATE 430
- Reserved Keywords 431
- Keywords and Variables 432
- Appendix E. Debug Aids 433
- Debug Aids 434
- Business Solutions 435
- Business Value Discussion 436
- Product Positioning 437
- System Profile Exec 439
- Defining Authorized Users 439
- Parameters 440
- Function IDs 441
- Appendix H. Security 443
- BMS Example 450
- Create the RFS Filepools 453
- Install Resource Definitions 453
- Update LSRPOOL Definitions 453
- Rename supplied Procedures 453
- Update CICSTART.PROC 454
- Format the RFS Filepools 455
- Create the Help Files 455
- Verify the Installation 456
- PI Configuration 457
- Bibliography 459
- VSE/ESA Version 2 Release 5 460
- Bibliography 439 461
- C for VSE/ESA (C/VSE) 462
- COBOL for VSE/ESA (COBOL/VSE) 462
- DB2 Server for VSE 462
- DL/I VSE 463
- PL/I for VSE/ESA (PL/I VSE) 463
- Trademarks 467
- Special characters 469
- Index 449 471
- Index 451 473
- Index 453 475
- Sending your comments to IBM 477
- SC34-5764-01 480
- REXX Guide 481
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