if(object instanceof WhereStatement) { WhereStatement where = (WhereStatement) object; doSomething(where); } Note that code like this usually means that your base class is missing a polymorphic method. i.e. doSomething() should be a method of Statement, possibly abstract, that is overridden by sub-classes.
We say Idris has strict evaluation, but this is for its run-time semantics. Being a fully dependently typed language, Idris has two phases where it evaluates things, compile-time and run-time. At compile-time it will only evaluate things which it knows to be total (i.e. terminating and covering all possible inputs) in order to keep type … Read more
Unboxed vs Boxed Data To support parametric polymorphism and laziness, by default Haskell data types are represented uniformly as a pointer to a closure on the heap, with a structure like this: (source: haskell.org) These are “boxed” values. An unboxed object is represented by the value itself directly, without any indirection or closure. Int is … Read more
Your expression is the same as: 1+(+(+2)) Any numeric expression can be preceded by – to make it negative, or + to do nothing (the option is present for symmetry). With negative signs: 1-(-(2)) = 1-(-2) = 1+2 = 3 and 1-(-(-2)) = 1-(2) = -1 I see you clarified your question to say that … Read more
(load-string “(+ 1 2)”)
Something like this? :%s/^\(\d\d\):\(\d\d\)/\=submatch(1)*60+submatch(2)/ When the replacement starts with a \= the replacment is interpreted as an expression. :h sub-replace-expression is copied below Substitute with an expression *sub-replace-expression* *sub-replace-\=* When the substitute string starts with “\=” the remainder is interpreted as an expression. This does not work recursively: a substitute() function inside the expression cannot … Read more
I think you’re looking for something like this: SET @queryString = ( SELECT CONCAT(‘INSERT INTO user_group (`group_id`,`user_id`) VALUES ‘, www.vals) as res FROM ( SELECT GROUP_CONCAT(qwe.asd SEPARATOR ‘,’) as vals FROM ( SELECT CONCAT(‘(59,’, user_id, ‘)’) as asd FROM access WHERE residency = 9 ) as qwe ) as www ); PREPARE stmt FROM @queryString; … Read more
It is a negation. However, you need to understand ANSI NULLs – a negation of a NULL is also a NULL. And NULL is a falsy truth value. Therefore, if any of your arguments is null, the result of @a = @b will be null (falsy), and a negation of that will also be a … Read more
No, if (c) is the same as if (c != 0). And if (!c) is the same as if (c == 0).
I’ve used PostgreSQL in an environment where we’re seeing 100K-2M new rows per day, most added to a single table. However, those rows tend to be reduced to samples and then deleted within a few days, so I can’t speak about long-term performance with more than ~100M rows. I’ve found that insert performance is quite … Read more