Referring to the Base and Current Frames

It is often necessary to refer to the base and current Frames (§13.4) within a FrameSetFrameSet, but it can be cumbersome having to obtain their indices from the BaseBase and CurrentCurrent attributes on each occasion. To make this easier, two macros, AST__BASE and AST__CURRENT, are defined in the “ast.h” header file and may be used to represent the indices of the base and current Frames respectively. They may be used whenever a FrameFrame index is required.

For example, when adding a new Frame to a FrameSet (§13.3), you could use the following to indicate that the new Frame is related to the existing current Frame, whatever its index happens to be:


\begin{terminalv}
AstFrame *frame;
AstMapping *mapping;
\par
...
\par
astAddFrame( frameset, AST__CURRENT, mapping, frame );
\end{terminalv}

Of course, the Frame you added would then become the new current Frame.