`sum` from `math` works on openArrays, but what you have supplied is an iterator. Unfortunately, the support for iterator adapters/consumers is poor in Nim at the moment.
It seems that the idiomatic way is collecting to a sequence and then summing (or, in other cases, acting on the values of the new collection) which is conceptually looks like a hack and is a tradeoff, when compared to a simple loop. Until a proper supports lands in the language, I get by with [zero_functional](https://github.com/zero-functional/zero-functional) lib, which allows the following syntax. The lib is not without its own quirks and limitations, though, but it works rather well for basic stuff. import tables, zero_functional let table = {"foo": 1, "bar": 2, "baz": 3}.toTable echo table.values --> drop(1).map(it * 2).sum() Run
