The DLL interface to join

Attachment produce two APIs, exec and eval.
Give them an api_call(intr argc, void* argv[]); c call convention.

The exec has method identifiers in the first argument. eval generally want the attachment to make a decision about a node pair, and their operator. The key value is char*, in my application. We can force the arguments to be either real pointers or int, via trickery. But the key can be anything, an image , a sound byte.  Match can be anything, a statistical distance, for example, but it must resolve into a step or skip with an optional output emit.

The first argument in the list is always the cursor, defined in cursor.h. If we wanted we can make it:
exec(Cursor* ptr); Then the Cursor structure can hold any argument list, and they would be mostly static.

Simple rules, the cursor has the methods, add one, the attachment has to initialize its own cursor.

Here is an initial classification of the commandlets at the console interface.

• Loading match functions, and attachments,
• Configure and stack instances.
• Initialize and configure the join and any overlay modes
• Grouping and interrogating cursors
• Groupting and interrogating attachment instances.
• Read and write the structured memory to disk
• Maintain static and dynamic argument lists and configuration

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