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authorMatt Doherty <matt.d.doc@gmail.com>2016-11-10 12:47:02 +0000
committerven <vendethiel@hotmail.fr>2016-11-10 13:47:02 +0100
commit0804650a9a50e51d3247cf1517040d63b1bb8f93 (patch)
tree9be6937f097c9b82cca11cca040c1a7d231948d9
parent94787745d58f559ddb10b0d6864b4d1bcab0adc4 (diff)
series of fixes and improvements (#2563)
-rw-r--r--kdb+.html.markdown39
1 files changed, 21 insertions, 18 deletions
diff --git a/kdb+.html.markdown b/kdb+.html.markdown
index 76f07f7b..772c8a47 100644
--- a/kdb+.html.markdown
+++ b/kdb+.html.markdown
@@ -256,7 +256,7 @@ l / => 5 2 3 4
/ Lists can also be used for indexing and indexed assignment
l[1 3] / => 2 4
l[1 3]: 1 3
-l / => 1 1 3 3
+l / => 5 1 3 3
/ Lists can be untyped/mixed type
l:(1;2;`hi)
@@ -290,6 +290,7 @@ last 1 2 3 / => 3
/ Take (#), drop (_) and find (?) are also useful working with lists
l:1 2 3 4 5 6 7 8 9
+l:1+til 9 / til is a useful shortcut for generating ranges
/ take the first 5 elements
5#l / => 1 2 3 4 5
/ drop the first 5
@@ -297,7 +298,7 @@ l:1 2 3 4 5 6 7 8 9
/ take the last 5
-5#l / => 5 6 7 8 9
/ drop the last 5
--5_l / => 1 2 3 4 5
+-5_l / => 1 2 3 4
/ find the first occurance of 4
l?4 / => 3
l[3] / => 4
@@ -397,7 +398,7 @@ k!t
/ => id| c1 c2 c3
/ => --| --------
/ => 1 | 1 4 7
-/ => 2 | 2 5 8
+/ => 2 | 3 5 8
/ => 3 | 3 6 9
/ We can also use this shortcut for defining keyed tables
@@ -455,7 +456,7 @@ f[2] / => 4
/ however using a dictionary as a single argument can overcome this
/ allows for optional arguments or differing functionality
d:`arg1`arg2`arg3!(1.0;2;"my function argument")
-{x[`arg1]+x[`arg2]}[d] / => 3.0
+{x[`arg1]+x[`arg2]}[d] / => 3f
/ Functions in q see the global scope
a:1
@@ -464,6 +465,7 @@ a:1
/ However local scope obscures this
a:1
{a:2;:a}[] / => 2
+a / => 1
/ Functions cannot see nested scopes (only local and global)
{local:1;{:local}[]}[] / throws error as local is not defined in inner function
@@ -494,11 +496,11 @@ t:([]name:`Arthur`Thomas`Polly;age:35 32 52;height:180 175 160;sex:`m`m`f)
/ equivalent of SELECT * FROM t
select from t / (must be lower case, and the wildcard is not necessary)
-/ => name age height
-/ => -----------------
-/ => Arthur 35 180
-/ => Thomas 32 175
-/ => Polly 52 160
+/ => name age height sex
+/ => ---------------------
+/ => Arthur 35 180 m
+/ => Thomas 32 175 m
+/ => Polly 52 160 f
/ Select specific columns
select name,age from t
@@ -523,6 +525,7 @@ select name, feet:floor height*0.032, inches:12*(height*0.032) mod 1 from t
/ => ------------------
/ => Arthur 5 9.12
/ => Thomas 5 7.2
+/ => Polly 5 1.44
/ Including custom functions
select name, growth:{[h;a]h%a}[height;age] from t
@@ -534,18 +537,18 @@ select name, growth:{[h;a]h%a}[height;age] from t
/ The where clause can contain multiple statements separated by commas
select from t where age>33,height>175
-/ => name age height
-/ => -----------------
-/ => Arthur 35 180
+/ => name age height sex
+/ => ---------------------
+/ => Arthur 35 180 m
/ The where statements are executed sequentially (not the same as logical AND)
select from t where age<40,height=min height
-/ => name age height
-/ => -----------------
-/ => Thomas 32 175
+/ => name age height sex
+/ => ---------------------
+/ => Thomas 32 175 m
select from t where (age<40)&(height=min height)
-/ => name age height
-/ => ---------------
+/ => name age height sex
+/ => -------------------
/ The by clause falls between select and from
/ and is equivalent to SQL's GROUP BY
@@ -585,7 +588,7 @@ t
/ => Polly 52 160 f
/ Insert however is in place, it takes a table name, and new data
-`t insert (`John;25;178;`m)
+`t insert (`John;25;178;`m) / => ,3
t
/ => name age height sex
/ => ---------------------