Dear Ertugrul, Thank you for your input.
To answer your question: Arrow notation has no support for what you want, so if you stick with it you will have to write the inner proc explicitly.
Oh. I was afraid of that.
However: The code may look much nicer, if you use applicative style for the outer computation using Applicative, Category and Profunctor [1]:
Thank you for the code. It looks much nicer than my code, which uses the arrow notation both for inner and outer computations.
If you prefer, you can use arrow notation for the inner computation.
This was a blind spot for me; I had not thought of mixing the arrow notation and the plain notation. This definitely helps writing a code when either the outer computation or the inner computation is simple. Unfortunately, sometimes both the outer computation and the inner computation involve many local variables, in which case I need the arrow notation for both, forcing me to write the inner proc explicitly inside the outer proc. If someone extends the arrow notation someday and makes this use case easier, that will be great. For now, avoiding the arrow notation for simple computations and writing two proc’s when both computations are complicated seems like a reasonable compromise to me. Thanks a lot! Best regards, Tsuyoshi