Re: Function composition using common argument - KX Learning Hub

Laura

Administrator
October 27, 2022 at 12:00 am
Q doesnt really offer built-in combinators as liberally as its ancestor language APL does. An elegant way to compose the projections of f1 and f2? You can lose the parens
```
q)c: f1[;a] f2[;a]@ 
q)c 3 
0n 0.5 0.5 0.3333333 0.25 0.2 0.1666667 0.1428571 0.125 0.1111111
```
Of course, if you have to do this often, you can write your own combinator. Call it cr for curry right:
```
q)cr:{x[;y]} 
q)c:('[;])over(f1;f2)cr:a  / Compose over (f1[;a];f2[;a]) 
q)c 3 
0n 0.5 0.5 0.3333333 0.25 0.2 0.1666667 0.1428571 0.125 0.1111111
```
Compose over a list of functions as many as you need.