On Sat, Mar 8, 2014 at 10:52 AM, Max Vlasov <max.vla...@gmail.com> wrote:
> On Fri, Mar 7, 2014 at 11:51 PM, Dominique Devienne <ddevie...@gmail.com>
> wrote:
>>
>> basically register_function('rpad', 'x', 'y', 'printf(''%-*s'', y,
>> x)') would register a 2-arg function (register_function's argc-2)
>> named $argv[0], which executes the following statement
>>
>> with args($argv[1], $argv[2], ... $argv[argc-2]) as (VALUES(?, ?))
>> select $argv[argc-1) from args;
>>
>
> Dominique, your variant is even better than using numbered parameters.
> If you use named ones supported by sqlite (:VVV) then sqlite will do
> the job of the textual replacement with bind api itself (
> 'printf(''%-*s'', :y,> :x)' )
>
> The small problem in this case is that there are two ways (times) to
> check whether named parameter exists in the expression.
No longer problem here :) SQLite3_Bind_Parameter_name is available at
the time of registration, so the prepared statement knows everything
about the number and the names of the parameters for full checking.
I have a working prototype, some things are left to do, but this
confirms that sqlite is content with the contexts and everything.
Examples:
SELECT RegisterExpressionFunction('myfunc', '45');
Select Myfunc()
45
SELECT RegisterExpressionFunction('mysum', 'x', ':x + :x');
select mysum(45)
90
SELECT RegisterExpressionFunction('mysumalt', '', '', '?1 + ?2');
select mysumalt(45, 67)
112
SELECT RegisterExpressionFunction('strconcat', 's1', 's2', ':s1||:s2');
Select strconcat('foo ', 'bar')
foo bar
Max
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