Evaluation of substrings

The following examples show how the assembler processes substrings depending on the value of the elements n, e1, and e2.

In the usual case, the assembler generates a correct substring of the specified length:

                Value of Variable   Character Value
Notation        Symbol              of Substring

'ABCDE'(1,5)                        ABCDE
'ABCDE'(2,3)                        BCD
'ABCDE'(2,*)                        BCDE
'ABCDE'(4,*)                        DE
'&C'(3,3)       ABCDE               CDE
'&PARAM'(3,3)   ((A+3)*10)          A+3

When e1 has a zero or negative value, the assembler generates a null string and issues error message ASMA093E.

                 Character Value
Notation         of Substring

'ABCDE'(0,5)     null character string
'ABCDE'(0,*)     null character string

When the value of e1 exceeds n, the assembler generates a null string and issues error message ASMA092E.

                Value of Variable   Character Value
Notation        Symbol              of Substring

'ABCDE'(7,3)                        null character string
'ABCDE'(6,*)                        null character string

When e2 has a value less than one, the assembler generates the null character string. If e2 is negative, the assembler also issues error message ASMA095W.

                Value of Variable   Character Value
Notation        Symbol              of Substring

'ABCDE'(4,0)                        null character string
'ABCDE'(3,-2)                       null character string

When e2 indexes past the end of the character expression (that is, e1+e2 is greater than n+1), the assembler issues warning message ASMA094I, and generates a substring that includes only the characters up to the end of the character expression specified.
```
                Value of Variable   Character Value
Notation        Symbol              of Substring

'ABCDE'(3,5)                        CDE
```

Figure 1 shows the results of an assembly of SETC instructions with different substring notations.

Figure 1. Sample assembly using substring notation

  Loc  Object Code    Addr1 Addr2  Stmt   Source Statement                                  HLASM R6.0       2008/07/11 17.48
                                      8 &STRING  SETC  'STRING'                                                 00008000
                                      9 &SUBSTR1 SETC  '&STRING'(0,4)                                           00009000
** ASMA093E Substring expression 1 less than 1; default=null - OPENC
                                     10 &SUBSTR2 SETC  '&STRING'(7,4)                                           00010000
** ASMA092E Substring expression 1 points past string end; default=null - OPENC
                                     11 &SUBSTR3 SETC  '&STRING'(3,0)                                           00011000
                                     12 &SUBSTR4 SETC  '&STRING'(3,-2)                                          00012000
** ASMA095W Substring expression 2 less than 0; default=null - OPENC
                                     13 &SUBSTR5 SETC  '&STRING'(3,4)                                           00013000
                                     14 &SUBSTR6 SETC  '&STRING'(3,5)                                           00014000
** ASMA094I Substring goes past string end; default=remainder
                                     15          END                                                            00015000

You can suppress the ASMA094I message by specifying the FLAG(NOSUBSTR) option or by setting the ACONTROL FLAG(NOSUBSTR) value. When this is done, the listing changes (Figure 2).

Figure 2. Sample assembly using substring notation with messages suppressed

  Loc  Object Code    Addr1 Addr2  Stmt   Source Statement                                  HLASM R6.0       2008/07/11 17.48
                                      7          ACONTROL FLAG(NOSUBSTR)
                                      8 &STRING  SETC  'STRING'                                                 00008000
                                      9 &SUBSTR1 SETC  '&STRING'(0,4)                                           00009000
** ASMA093E Substring expression 1 less than 1; default=null - OPENC
                                     10 &SUBSTR2 SETC  '&STRING'(7,4)                                           00010000
** ASMA092E Substring expression 1 points past string end; default=null - OPENC
                                     11 &SUBSTR3 SETC  '&STRING'(3,0)                                           00011000
                                     12 &SUBSTR4 SETC  '&STRING'(3,-2)                                          00012000
** ASMA095W Substring expression 2 less than 0; default=null - OPENC
                                     13 &SUBSTR5 SETC  '&STRING'(3,4)                                           00013000
                                     14 &SUBSTR6 SETC  '&STRING'(3,5)                                           00014000
                                     15          END                                                            00015000

Character (SETC) expressions can be used only in conditional assembly instructions. Table 1 shows examples of using character expressions.

Table 1. Use of character expressions
Used in	Used as	Example
SETC instruction	Operand	`&C SETC 'STRING0'`
AIF or SETB instruction	Character string in character relation	`AIF ('&C' EQ 'STRING1').B`
Substring notation	First part of notation	`'SELECT'(2,5) returns 'ELECT'`
Built-in functions	Operand	`&VAR SETC (LOWER '&twenty.&six') &AB SETA A2B('10')`