Hello Bitcoin-Dev,

I hope this isn't out of line, but I joined the mailing list to try to start a discussion on adding opcodes to make Script Turing Pseudo-Complete as Wright suggested is possible.

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In line with Wright's suggestion, I propose adding a return stack alongside the, already existing, control stack.

The principle opcodes (excluding conditional versions of call and return_from) needed are

OP_DEFINITION_START FunctionName:  The code that follows is the definition of a new function to be named TransactionSenderAddress.FunctionName.  If this function name is already taken, the transaction is marked invalid.  Within the transaction, the function can be called simply as FunctionName.

OP_DEFINITION_END:  This ends a function definition

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OP_CALL Namespace.FunctionName Value TransactionFee:  This marks the transaction as valid.  It also pushes the current execution location onto the return stack, debits the calling transaction by the TransactionFee and Value, and creates a new transaction specified by Namespace.FunctionName with both stacks continued from before (this may be dangerous, but I see no way around it) with the specified value.

OP_RETURN_FROM_CALL_AND_CONTINUE:  This pops the top value off the return stack and continues from the specified location with both stacks in tact.

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It would also be useful if a transaction can create another transaction arbitrarily, so to prepare for that, I additionally propose

OP_NAMESPACE:  Pushes the current namespace onto the control stack

This, combined with the ability to make new transactions arbitrarily would allow a function to pay its creator.

I understand that this isn't all that is needed, but I think it's a start.  I hope this proposal has met you all well,

Luke Durback