Course of Raku / Advanced / Operators / Traits and pragmas 🆕 / Exercises

A writable parameter

Problem

By default a subroutine’s parameters are read-only, so a routine cannot change the caller’s variable. The is rw trait removes that restriction.

Write a subroutine double whose single parameter is marked is rw, and which doubles it in place ($n *= 2). Call it on a variable holding 21, then print the variable to show that it has become 42.

Example

The program prints:

42

Solution

✅ See the solution

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