Zulip Chat Archive

Stream: new members

Topic: A version of add_le_add for indexed sums


Ryan Smith (Sep 03 2025 at 18:55):

I have been trying to find this result with leanexplore and moogle but without luck:

I have a finite set s of complex numbers and for each z \in s I have an inequality |z| \le |w|. Isn't there a version of add_le_add for an indexed sum?

 z  s, z \le  z  s, w

Eric Wieser (Sep 03 2025 at 18:55):

@loogle "sum_le_sum"

loogle (Sep 03 2025 at 18:55):

:search: List.Forall₂.sum_le_sum, List.sum_le_sum, and 22 more

Eric Wieser (Sep 03 2025 at 18:56):

From that list, docs#Finset.sum_le_sum is what you want

Eric Wieser (Sep 03 2025 at 18:57):

A better query would have been

@loogle: ∑ z ∈ ?s, _ ≤ ∑ z ∈ ?s, _

loogle (Sep 03 2025 at 18:57):

:search: Finset.sum_le_sum, Finset.exists_le_of_sum_le, and 19 more

Ryan Smith (Sep 03 2025 at 20:23):

Thanks, I need to get comfortable with loogle since it seems quite powerful for finding results.


Last updated: Dec 20 2025 at 21:32 UTC