Application and indexing¶
All the forms of dot¶
In q, there are several ways to apply a function and index a variable. Underlying them all is the ur-function Apply/Index
pronounced dot. Application of the rank-n function
f to a list of arguments
v of count n is expressed:
f . v
The only place you can fall from
is where it’s at; and when you’re down,
you’re not there – that’s why.
— Alastair Howard Robertson
Application of the unary function
w is expressed:
g . enlist w
sugar for which is
Even more simply:
Brackets are more sugar:
f[first v;…;last v] g[w]
Maximize readability by using the simplest syntax available.
Brackets and parens¶
All functions can be applied with bracket notation. Infix and prefix syntax is usually clearer and preferable.
+[2;2] 2+2 til til 5
Not always, particularly when composing the left argument of an infix.
Short expressions within brackets or parentheses are clearer than long expressions. Bracket notation can avoid parenthesizing a longer expression.
+/[foo goo v] / less clear (+/) foo goo v / more clear bar[(+//)m; goo v] / less clear ((+//)m) bar goo v / clearer? +//[m] bar goo v / clear
Minimize the distance between opening and closing brackets and parentheses.