AutoGen: Index Assignments

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## 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 assiged 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 section 3.6.13 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") +]

This document was generated by Bruce Korb on February 23, 2004 using texi2html