assumeSafeAppend and purity
Jonathan M Davis
jmdavisProg at gmx.com
Mon Feb 6 17:46:01 PST 2012
At present, assumeSafeAppend isn't pure - nor is capacity or reserve. AFAIK,
none of them access any global variables aside from GC-related stuff (and new
is already allowed in pure functions). All it would take to make them pure is
to mark the declarations for the C functions that they call pure (and those
functions aren't part of the public API) and then mark them as pure. Is there
any reason why this would be a _bad_ idea?
Appender runs into similar difficulties. Would it make sense to just mark the
various memory-related functions in core.memory as pure (or at least some
subset of them)? The fact that they aren't in spite of the fact that they
involve memory like new does really makes it hard to both use pure and
optimize code in a number of cases - especially when dealing with arrays. We
might also want to just mark malloc as pure for the same reason.
What are the downsides to doing this? It probably wouldn't be a good idea to
mark functions like free pure, but the ones that involve allocating or
reallocating memory seem like good candidates for it.
- Jonathan M Davis
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