support for instantaneous loops within activities

[mterber]

Is your feature request related to a problem? Please describe. Sometimes it is required to process arrays in the context of a running activity, e.g. for a copy operation like in the following example:

activity RF_sendCmdWord (dataTx: [...]uint8)(...) returns int8
    var tx_bytes: [SPI_DATA_SIZE]uint8 // SPI transmit buffer.
    var rx_bytes: [SPI_DATA_SIZE]uint8 // SPI receive buffer.
    var tx_len: uint16 = 0 // Number of bytes to send.
    ...
    // Send the provided tx data.
    memcpy2spi(dataTx, 0, tx_len, dataLen)(tx_bytes)
    res = run SPI_txRxBytes(tx_bytes, tx_len)(rx_bytes)
    ...
end

Here, dataTx shall be copied to _txbytes. This requires to loop over the array bytes within a single reaction. However, this is not allowed in activities, only in functions. So whenever I have to loop over arrays in an activity I have to create special function for that purpose.

Describe the solution you'd like I would like to be able to execute instantaneous loops within activities directly.

[frameworklabs]

I think this request would confuse more than it helps. I like the simple semantics currently in place. Creating instantaneous helper functions as you did with memcpy seem to me to be the better approach.

[mterber]

Maybe a compromise could be to support variable array lengths. This way, I could at least reuse the same (generic) memcpy() function for different activities that deal with arrays of different size. Otherwise you end up with an impressive line-up of helper functions that, in principle, do exactly the same thing.

[frameworklabs]

Maybe some limited generic support like below would help here some day:

function memcpy<L, T>(from: [L]T)(to: [L]T)
    var i: nat32
    while i < L repeat
        to[i] = from[i]
    end
end

[mterber]

That sounds good from a user's point of view. :+1: