Inverted syntax: Difference between revisions
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The task is to demonstrate support for inverted syntax forms within the language by showing both the traditional and inverted forms.
=={{header|6502 Assembly}}==
Conditional branches are limited in the range they can branch; all branch statements cannot be more than 127 or -128 bytes away from their destination.
The below example will result in an assemble time error. The intended action is that the X variable is decremented, and execution returns to the top of the loop. However, the branch is simply too far away.
<lang 6502asm>loop_MySubroutine:
; more than 127 bytes of code
dex
bne loop_MySubroutine ;assembler will display an error message that the branch is too far away.
; rest of program</lang>
The easiest way to overcome this limitation is to invert the branch condition and place a <code>JMP</code> back to the loop under it.
An unconditional <code>JMP</code> moves the program counter to the specified location, no matter where that is.
<lang 6502asm>loop_mySubroutine:
; more than 127 bytes of code
dex
beq continue
JMP loop_mySubroutine
continue:
; rest of program</lang>
Now, what happens is that the opposite condition is checked. If X = 0, execution branches 3 bytes forward to "continue." Otherwise, the statement underneath the branch is executed, which is a jump back to the top.
=={{header|Ada}}==
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