[CakeML-dev] New string/bytearray operations

Ramana Kumar Ramana.Kumar at cl.cam.ac.uk
Mon Mar 20 05:29:10 UTC 2017

I've been rethinking these primitives after the discussion at the last
hangout, and have come up with a different set altogether. Can you see a
simpler or more elegant approach to the one described below?

Here is the new approach I am considering:

4 copying primitives in the source language going from string/bytearray to
The source comes with an offset and a length to copy.
If the destination is a string, a new string is created. If the destination
is a bytearray, it must be provided.

Concatenation (of lists of strings/arrays) and conversions between (whole)
strings and (whole) bytearrays can be implemented in the basis library in
terms of these primitives. And the primitives should be efficiently
implementable in terms of a byte-based memcpy primitive further down.
(There will need to be bounds checking in the source-level semantics (i.e.,
Subscript exception can be raised), and this will sometimes be unfortunate
(i.e., when obviously in bounds), but I don't think this is too costly.)

On 14 March 2017 at 16:52, Ramana Kumar <Ramana.Kumar at cl.cam.ac.uk> wrote:

> Hi all,
> I've started adding string/bytearray conversion and concatenation
> primitives (issues 244 and 245). Before getting too deep into updating
> the compiler etc., may I request a review of the semantics? Here they
> are:
> https://github.com/CakeML/cakeml/commit/67dd15bbd03f516be618ba72f1d56a
> 2764209263
> I noticed that v_to_char_list might be better as vs_to_char_list, to
> be run after v_to_list (rather than duplicating its
> list-deconstruction functionality). But I leave such refactoring for
> another time.
> Cheers,
> Ramana
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