2.3 Assigning an Index to a Definition

In AutoGen, every name is implicitly an array of values. When assigning values, they are usually implicitly assigned to the next highest slot. They can also be specified explicitly:

mumble[9] = stumble;
mumble[0] = grumble;

If, subsequently, you assign a value to mumble without an index, its index will be 10, not 1. If indexes are specified, they must not cause conflicts.

#define-d names may also be used for index values. This is equivalent to the above:

#define FIRST 0
#define LAST  9
mumble[LAST]  = stumble;
mumble[FIRST] = grumble;

All values in a range do not have to be filled in. If you leave gaps, then you will have a sparse array. This is fine (see FOR - Emit a template block multiple times). You have your choice of iterating over all the defined values, or iterating over a range of slots. This:

[+ FOR mumble +][+ ENDFOR +]

iterates over all and only the defined entries, whereas this:

[+ FOR mumble (for-by 1) +][+ ENDFOR +]

will iterate over all 10 "slots". Your template will likely have to contain something like this:

[+ IF (exist? (sprintf "mumble[%d]" (for-index))) +]

or else "mumble" will have to be a compound value that, say, always contains a "grumble" value:

[+ IF (exist? "grumble") +]