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underlying reason of back tick

analyst_tech_jo
New Contributor
I am trying to come up with what backtick really means. hopen backtick means localhost key backtick returns contexts in a q session. I am guessing it is internally referencing a dictionary. Backtick in a queue SQL means modifying that table.
3 REPLIES 3

quintanar401
New Contributor
You could think of it as the default symbol so its meaning depends on a function - hopen, key, vs/sv and etc - that accepts a sym param.

WBR, Andrey.

среда, 2 декабря 2015 г., 19:40:42 UTC+3 пользователь analyst написал:
I am trying to come up with what backtick really means.

hopen backtick means localhost

key backtick returns contexts in a q session. I am guessing it is internally  referencing a dictionary.

Backtick in a queue SQL means modifying that table.

the backtick ` is the null value for the datatype symbol.
what functions like hopen, key, ...  do with it depends on the function.

Aaron_Davies
New Contributor
backtick marks literal symbols — it's a type signifier, like thetrailing letters used for the other types (0b "0 as a boolean", 7h "7as a short (integer), 1f "one as a (64-bit) float", etc.)it's like leading unpaired apostrophe from lisp, if that helps at allbacktick on its own is the null symbol and has various meanings tovarious functionsnote that key` is missing `, the relative name of the default context`. — the implied relationship is that all contexts are siblings at thesame (first) level in a tree whose root is named ` (the empty stringas a sym), and the default context is also (relatively) named `;absolute names are formed by adding a dot between the parent andchild, so the default context is named `. (empty string, dot, emptystring); key`. is a list of the contents of the default namespace,key`.q of the .q namespace, etc.in some cases, a symbol is interpreted as the name of a globalvariable, and some functions will behave differently when given avariable to operate on by its name (f`x) rather than its value (f x);this can be thought of as somewhat like pass-by-name vs.pass-by-value, though keep in mind it's not completely analogousspecifically, qsql update and delete (as well as various functionslike @, ., ! in the sense of modifying table keying, xkey, etc.)modify the given table (or other thing) and save it back to memorywhen given it by name (with a backtick), but return the modified tablewhen given it by value (without a backtick)On Wed, Dec 2, 2015 at 11:33 AM, analyst wrote:> I am trying to come up with what backtick really means.>> hopen backtick means localhost>> key backtick returns contexts in a q session. I am guessing it is internally referencing a dictionary.>> Backtick in a queue SQL means modifying that table.>> --> You received this message because you are subscribed to the Google Groups "Kdb+ Personal Developers" group.> To unsubscribe from this group and stop receiving emails from it, send an email to personal-kdbplus+unsubscribe@googlegroups.com.> To post to this group, send email to personal-kdbplus@googlegroups.com.> Visit this group at http://groups.google.com/group/personal-kdbplus.> For more options, visit https://groups.google.com/d/optout.-- Aaron Daviesaaron.davies@gmail.com