| Programming with Ophis | ||
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Labels are an important part of your code. However, since each label must normally be unique, this can lead to "namespace pollution," and you'll find yourself going through ever more contorted constructions to generate unique label names. Ophis offers two solutions to this: anonymous labels and temporary labels. This tutorial will cover both of these facilities, and also introduce the aliasing mechanism.
Temporary labels are the easiest to use. If a label begins with an underscore, it will only be reachable from inside the innermost enclosing scope. Scopes begin when a .scope statement is encountered. This produces a new, inner scope if there is another scope in use. The .scend command ends the innermost currently active scope.
We can thus rewrite our header data using temporary labels, thus allowing the main program to have a label named next if it wants.
.word $0801
.org $0801
.scope
.word _next, 10 ; Next line and current line number
.byte $9e," 2064",0 ; SYS 2064
_next: .word 0 ; End of program
.scend
.advance 2064 |
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| Assembling the code | Anonymous labels |