how to do this meta-programming? print the address of random element's address of a variable length of arrays?
mingwu at gmail.com
Sun Sep 13 18:24:01 UTC 2020
On Sunday, 13 September 2020 at 10:16:46 UTC, Paul Backus wrote:
> On Sunday, 13 September 2020 at 07:00:36 UTC, mw wrote:
>> Here it is: D wrapper for https://ta-lib.org/
>> I end up using C macro to generate D functions, the single
>> template is this one:
>> #define DECL_TA_FUNC(TA_FUNC, FUNC_INS, FUNC_OUTS,
>> expected_lookback) __NL__\
> The most straightforward way to do this in D is with a mixin
> template. Something like:
> mixin template DECL_TA_FUNC(string TA_FUNC, FUNC_INS,
> FUNC_OUTS, int expected_lookback)
> bool impl(...)
> // ...
> // Could also wrap the whole function in a string mixin,
> // but this is easier.
> mixin("alias ", TA_FUNC, " = impl;");
> Which you would then use like this:
> mixin DECL_TA_FUNC!(
> Tuple!(int, "MA_optInTimePeriod", TA_MAType, "opInMAType"),
> Tuple!(double, "outMA"),
> MA_optInTimePeriod - 1
Thanks, I will do the exercise some other day.
But, I'd reflect on my experience so far on compile-time
meta-programming in D as a novice user, the big problems are:
-- in D, there are too many choices, with no clear guideline
which one is *THE* one to use for a particular purpose: language
or library mechanisms? mixin? template? AliasSeq / aliasSeqOf?
Tuple? (non-)?-eponymous version of ...?; and even for a
particular option, e.g. Tuple!(int, "MA_optInTimePeriod",
TA_MAType, "opInMAType"), there are choices to use either token
(int) or string ("MA_optInTimePeriod"). And user does not have a
strong guide on which choice is *THE* way to proceed. Each
mechanism seems to have / fit a particular purpose, but when you
start to use it, you'll probably find there are new problems
come-in later, and you want to revisit the choice you made
By contrast, in C: there is only *ONE* mechanism, i.e. macro,
-- in D, there is no easy way to convert between token <==>
string. Given a token, does token.stringof always work to paste
with other strings to generate a new token? and given a string,
does mixin!"string" always work to be a valid token?
By contrast, in C: there is only *ONE* way: xxx ## yyy.
-- in D, there is no easy way to see directly the generated
source code by the compiler at compile-time, which makes the
debug difficult during development.
By contrast, in C: one can easily see the result via: cpp -P
foo.h > foo.c
As I said earlier, I'm not very experienced with C macros either,
however with some googling, I was able to work out a C macro
version to generate D code; but with all the help so far, I still
have no confidence that I can work out a solution in D to
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