HLASM Language Reference

SET Symbols
The dimension (the maximum value of the subscript) of a subscripted SET symbol
is not determined by the explicit or implicit declaration of the symbol. The
| dimension specified can be exceeded in later SETx instructions. Note, however,
| that increasing the dimension of a subscripted SET symbol also increases the
| storage required. For example, referencing only &ARRAY(1000000) still causes the
| preceding 999999 elements to be allocated. You can determine the maximum
| subscript using the N' attribute (see “Number Attribute (N')” on page 336).
The subscript can be a subscripted SET symbol.
Created SET Symbols
The assembler can create SET symbols during conditional assembly processing
from other variable symbols and character strings. A SET symbol thus created has
the form &(e), where e represents one or more of the following:
Variable symbols, optionally subscripted
Strings of alphanumeric characters
Other created SET symbols
After substitution and concatenation, e must consist of a string of up to 62
alphanumeric characters, the first of which is alphabetic. The assembler considers
| the preceding ampersand and this string as the name of a SET variable. If this
| created SET symbol has the same name as an existing SET symbol, they are
| treated as identical. If this created SET symbol does not have the name of any
| existing SET symbol, the usual rules for assigning type and scope apply.
You can use created SET symbols wherever ordinary SET symbols are permitted,
| including declarations. A created SET symbol may not match the name of a
| system variable symbol, nor the name of a symbolic parameter in a macro
| prototype statement. You can also nest created SET symbols in other created SET
| symbols.
Consider the following example:
&ABC(1) SETC
'MKT','27','$5'
Let &(e) equal &(&ABC(&I)QUA&I).
&I &ABC(&I) Created SET Symbol Comment
1 MKT &MKTQUA1 Valid
2 27 &27QUA2 Invalid: character after '&' not alphabetic
3 $5 &$5QUA3 Valid
4 &QUA4 Valid
| The name of a created SET symbol cannot match the name of a system variable
| symbol or of a symbolic parameter in a macro definition.
The created SET symbol can be thought of as a form of indirect addressing. With
nested created SET symbols, you can perform this kind of indirect addressing to
any level.
In another sense, created SET symbols offer an associative storage facility. For
example, a symbol table of numeric attributes can be referred to by an expression
of the form &(&SYM)(&I) to yield the Ith attribute of the symbol name in &SYM. As
Chapter 9. How to Write Conditional Assembly Instructions 323