I have a list
filter:((in;`name;`betsy`robert`tom);(>;`age;43));
and I would like to get the following list representation out of it
"((in;`name;`betsy`robert`tom);(>;`age;43))"
What I found so far is this:
flatten:{[alist]
$[(count alist)~count raze alist;:alist;:flatten raze alist];
};
";" sv string raze flatten[filter]
/ gives: "in;name;betsy;robert;tom;>;age;43"
which loses the nested lists in the filter list.
credits to: https://lifeisalist.wordpress.com/2009/07/10/p07-flatten-a-nested-list-structure/
Thanks!
I think the command you are looking for is .Q.s or .Q.s1 which return kdb code in plain text:
q).Q.s1 filter
"((in;`name;`betsy`robert`tom);(>;`age;43))"
It should be noted that the output of these functions is limited by \c.
Related
I have a string say example "https://www.google.com" and a count of paging say 5
how do i iterate the URL to append p/page=incrementing numbers of paging and store the result in a variable as list?
"https://www.google.com/page=1"
"https://www.google.com/page=2"
"https://www.google.com/page=3"
"https://www.google.com/page=4"
"https://www.google.com/page=5"
So the end result will look like this having a variable query_var which will hold a list of string example below
query_var:("https://www.google.com/page=1";"https://www.google.com/page=2";"https://www.google.com/page=3";"https://www.google.com/page=4";"https://www.google.com/page=5");
count query_var \\5
You can use the join function , with the each-right adverb /:
query_var: "https://www.google.com/page=" ,/: string 1_til 6
Make it a function to support a varied count of pages:
f:{"https://www.google.com/page=" ,/: string 1_til x+1}
q)10=count f[10]
1b
Q1
You don’t even need a lambda to make this a function. It’s a sequence of unary functions, so you can compose them.
q)f: "https://www.google.com/page=",/: string ::
q)f 1+til 6
"https://www.google.com/page=1"
"https://www.google.com/page=2"
"https://www.google.com/page=3"
"https://www.google.com/page=4"
"https://www.google.com/page=5"
"https://www.google.com/page=6"
Q2
q)("https://www.google.com";;"info/history")
enlist["https://www.google.com";;"info/history"]
q)"/"sv'("https://www.google.com";;"info/history")#/: string `aapl`msft`nftx
"https://www.google.com/aapl/info/history"
"https://www.google.com/msft/info/history"
"https://www.google.com/nftx/info/history"
List notation is syntactic sugar for enlist. The list with a missing item is a projection of enlist and can be iterated.
Again, a sequence of unaries is all composable without a lambda:
q)g: "/"sv'("https://www.google.com";;"info/history")#/: string ::
q)g `aapl`msft`nftx
"https://www.google.com/aapl/info/history"
"https://www.google.com/msft/info/history"
"https://www.google.com/nftx/info/history"
If you can assume a unique character that doesn't appear elsewhere in your url (e.g. #) then ssr is a simple and easily-readable approach:
ssr["https://www.google.com/page=#";"#";]each string 1+til 5
ssr["https://www.google.com/#/info/history";"#";]each string`aapl`msft`nftx
Using q’s like function, how can we achieve the following match using a single regex string regstr?
q) ("foo7"; "foo8"; "foo9"; "foo10"; "foo11"; "foo12"; "foo13") like regstr
>>> 0111110b
That is, like regstr matches the foo-strings which end in the numbers 8,9,10,11,12.
Using regstr:"foo[8-12]" confuses the square brackets (how does it interpret this?) since 12 is not a single digit, while regstr:"foo[1[0-2]|[1-9]]" returns a type error, even without the foo-string complication.
As the other comments and answers mentioned, this can't be done using a single regex. Another alternative method is to construct the list of strings that you want to compare against:
q)str:("foo7";"foo8";"foo9";"foo10";"foo11";"foo12";"foo13")
q)match:{x in y,/:string z[0]+til 1+neg(-/)z}
q)match[str;"foo";8 12]
0111110b
If your eventual goal is to filter on the matching entries, you can replace in with inter:
q)match:{x inter y,/:string z[0]+til 1+neg(-/)z}
q)match[str;"foo";8 12]
"foo8"
"foo9"
"foo10"
"foo11"
"foo12"
A variation on Cillian’s method: test the prefix and numbers separately.
q)range:{x+til 1+y-x}.
q)s:"foo",/:string 82,range 7 13 / include "foo82" in tests
q)match:{min(x~/:;in[;string range y]')#'flip count[x]cut'z}
q)match["foo";8 12;] s
00111110b
Note how unary derived functions x~/: and in[;string range y]' are paired by #' to the split strings, then min used to AND the result:
q)flip 3 cut's
"foo" "foo" "foo" "foo" "foo" "foo" "foo" "foo"
"82" ,"7" ,"8" ,"9" "10" "11" "12" "13"
q)("foo"~/:;in[;string range 8 12]')#'flip 3 cut's
11111111b
00111110b
Compositions rock.
As the comments state, regex in kdb+ is extremely limited. If the number of trailing digits is known like in the example above then the following can be used to check multiple patterns
q)str:("foo7"; "foo8"; "foo9"; "foo10"; "foo11"; "foo12"; "foo13"; "foo3x"; "foo123")
q)any str like/:("foo[0-9]";"foo[0-9][0-9]")
111111100b
Checking for a range like 8-12 is not currently possible within kdb+ regex. One possible workaround is to write a function to implement this logic. The function range checks a list of strings start with a passed string and end with a number within the range specified.
range:{
/ checking for strings starting with string y
s:((c:count y)#'x)like y;
/ convert remainder of string to long, check if within range
d:("J"$c _'x)within z;
/ find strings satisfying both conditions
s&d
}
Example use:
q)range[str;"foo";8 12]
011111000b
q)str where range[str;"foo";8 12]
"foo8"
"foo9"
"foo10"
"foo11"
"foo12"
This could be made more efficient by checking the trailing digits only on the subset of strings starting with "foo".
For your example you can pad, fill with a char, and then simple regex works fine:
("."^5$("foo7";"foo8";"foo9";"foo10";"foo11";"foo12";"foo13")) like "foo[1|8-9][.|0-2]"
Similarly to this question about json_extract_path_text, when I run this query in Redshift, I would expect json_extract_array_element_text to remove the backslashes from the "\"b\"" value:
select
j,
json_extract_array_element_text(j, 0) as a
from (select '["\\"b\\""]' as j);
Instead, it appears that the string value is extracted verbatim, and the results look like this:
["\"b\""]
\"b\"
Is this intentional? If yes, what would be the idiomatic way to remove the backslashes?
In essence, I want to take an array and create a single string with the elements of said array separated by a newline.
I have an array named $zones. Outputting the reference to $zones confirms it's an array.
The following code:
print_log(Dumper($zones));
print_log('-------');
print_log(Dumper(join("\n",$zones)));
results in the following output
[2013-06-15 16:23:29 -0500] info [dnsadmin] $VAR1 = [
'fake.com25',
'fake.com2',
'fake.com27',
'fake.com43',
'fake.com41',
'fake.com40',
'fake.com39',
'fake.com37',
'fake.com36',
'fake.com35',
'fake.com31',
'fake.com56',
'fake.com55',
'fake.com54',
'fake.com53',
'fake.com52',
'fake.com51',
'fake.com50',
'fake.com49',
'fake.com48',
'fake.com42',
'fake.com38',
'fake.com34',
'fake.com33',
'fake.com32',
'fake.com30',
'fake.com29',
'fake.com28',
'fake.com26',
'fake.com24',
'fake.com23',
'fake.com69',
'fake.com68',
'fake.com67',
'fake.com66',
'0',
'fake.com44',
'fake.com45',
'fake.com46',
'fake.com278'
];
[2013-06-15 16:23:29 -0500] info [dnsadmin] -------
[2013-06-15 16:23:29 -0500] info [dnsadmin] $VAR1 = 'ARRAY(0x170cf0d8)';
I really don't want to loop over this array manually. Can someone explain why the join() function is returning the name of the type along with a hex number?
How to do is explained well by user1937198, but why it works this way?
It's simple:
$zones is not an array. It's an array reference.
join works on lists. So if you do:
join("\n",$zones)
You essentially are calling join on a single-element list. And the element is a reference, which happens to stringify to ARRAY(0x170cf0d8).
To make it work correctly you have to dereference it, and it is done by prefixing with real datatype (# or %, or in some cases $).
This can be written like this: #$zones, or (some, including me, say that it's more readable) as: #{ $zones }.
This is important when you're having nested structures, because while you can have plain array as a variable, when you're dealing with nested data structures, it's always references.
what you want is join("\n",#{$zones}))
$zones is array reference and to join array values you have to dereference it first by prefixing scalar $zones with #
print_log(Dumper(join("\n",#$zones)));
For more info there is short tutorial on references:
http://perldoc.perl.org/perlreftut.html#NAME
I want to grab the first char of a var string and the first char of the following caracter
Example:
$var1 = "Jean-Martin"
I want a way to grab the first letter "J" then I want to take the first char following the "-" (dash) which is "M".
Something like this?
$initial1 = $var1[0]
$initial2 = $var1.Split('-')[1][0]
Strings in Powershell use the System.String class from the .Net framework. As such, they are indexable to retrieve individual characters and have many methods available such as the Split method used above.
See the documentation here.
$var1 = "Jean-Martin"
To get the first character:
$var1[0]
To get the first character after the dash:
$characterToSeek = '-'
$var1[$var1.IndexOf($characterToSeek)+1]
Another option using regex:
PS> $var1 -replace '^(.)[^-]+-(.).+$','$1$2'
JM