Hi Olaf,

Are you asking if

	run $ (const y) <$> normal 0 1 

has the same cost as

	run $ return y

for some interpreter `run`?

Yes, the cost is the same.  In do-notation, we would have

	run $ do
		x <- normal 0 1
		return $ (const y x)

Since `const y` never forces `x`, no time is spent evaluating `run $ normal 0 1`.  That is basically what I mean by saying that the language is lazy.

-BenRI

Hi,

My program BAli-Phy implements probabilistic programming with models 
written as Haskell programs.

http://www.bali-phy.org/models.php

Dear Benjamin, 

last time you announced BAli-Phy I pestered you with questions about
semantics. In the meantime there was a discussion [1] on this list
regarding desirable properties of probabilistic languages and monads in
general. A desirable property of any probabilistic language is that
when you define a distribution but map a constant function over it,
then this has the same computational cost as returning the constant
directly. Can you say anything about that? 

Cheers,
Olaf

[1] 
https://mail.haskell.org/pipermail/haskell-cafe/2020-November/132905.html