HLASM Language Reference

AGO Instruction
Example:
MACRO
&NAME MOVE &T,&F
AIF (T'&T EQ 'F').FIRST Statement 1
AGO .END Statement 2
.FIRST AIF (T'&T NE T'&F).END Statement 3
&NAME ST 2,SAVEAREA
L
2,&F
ST
2,&T
L
2,SAVEAREA
.END MEND Statement 4
Statement 1 determines if the type attribute of the first macro instruction operand is
the letter F. If the type attribute is the letter F, Statement 3 is the next statement
processed by the assembler. If the type attribute is not the letter F, Statement 2 is
the next statement processed by the assembler.
Statement 2 indicates to the assembler that the next statement to be processed is
Statement 4 (the statement named by sequence symbol .END).
Computed AGO Instruction
The computed AGO instruction makes branches according to the value of an
arithmetic expression specified in the operand.
►►──┬─────────────────┬──AGO────────────────────────────────────────►
└─sequence_symbol─┘
┌─,───────────────┐
►──(arithmetic_expression)
── ▼ ─sequence_symbol─┴─────────────────────►◄
sequence_symbol
is a sequence symbol.
arithmetic_expression
is an arithmetic expression the assembler evaluates to k, where k lies between
1 and n (the number of occurrences of sequence_symbol in the operand field)
inclusive. The assembler branches to the k-th sequence symbol in the list. If k
is outside that range, no branch is taken.
In the following example, control passes to the statement at .THIRD if &I= 3.
Control passes through to the statement following the AGO if &I is less than 1 or
greater than 4.
Cont.
AGO (&I).FIRST,.SECOND, X
.THIRD,.FOURTH
Alternative Format for AGO Instruction
The alternative statement format is allowed for computed AGO instructions. The
above example could be coded as follows:
Cont.
AGO (&I).FIRST, X
.SECOND,
X
.THIRD,
X
.FOURTH
Chapter 9. How to Write Conditional Assembly Instructions 393