kdb - resolving nested function when printing outer function body

Question

I would like to print the function definition of any nested function when printing the definition of the outer function. Example:

g:{sin x}
f:{cos g x}

When I print f I get {cos g x} but I want to get {cos {sin x} x}

Thanks for the help

Alex R. · Accepted Answer · 2018-06-19 13:55:00Z

4

From what I am aware it is not possible to achieve that with in-build functions.

You can attempt to write your own function that does that but it will be a pain in the end. Something like this maybe:

q)m:string[v]!string value each v:value[f][3] except `

which creates a dictionary m :

q)m
,"g"| "{sin x}"

When given a function value returns a list containing (bytecode;parameters;locals(context;globals);constants[0];...;constants[n];definition)

However, if we pass a symbol to value it returns the value of that symbol (or function definition in this case).

You can then use ssr to replace the functions in f with the function definitions stored in your dictionary m.

q)ssr/[last value[f];key m;value m]
"{cos {sin x} x}"

but to ensure that your function is stable and adaptable to different functions would be very difficult.

For more details about how value have a look here: https://code.kx.com/q/ref/metadata/#value

answered Jun 19, 2018 at 13:32

Alex R.

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1 Comment

Note - your value[f][9] is version specific. Value only returns 5 items in v3.4 and prior. last might work for now but could be subject to change