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Basic lemmas about sequences #187

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@affeldt-aist affeldt-aist commented Apr 23, 2020

The purpose of this PR is to add a file sequences.v to gather standard definitions and lemmas about sequences. It certainly deserves to be improved (completed and generalized) but maybe it is worth having it as soon as possible to have a place to share lemmas, e..g, for increasing sequences, and to defer improvements to future PRs (PR #207 is such a PR). There is also a file sequences_examples.v that defines a few standard sequences and proves a few lemmas about them, mostly as a test bed.

@affeldt-aist affeldt-aist force-pushed the mathcomp_master_sequences branch 2 times, most recently from 4796075 to aeb0546 Compare April 24, 2020 18:04
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@affeldt-aist affeldt-aist added this to the 0.3.0 milestone May 7, 2020
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I will start rebasing this branch

@CohenCyril CohenCyril mentioned this pull request May 7, 2020
@CohenCyril CohenCyril force-pushed the mathcomp_master_sequences branch 7 times, most recently from 26c7366 to 7d7c97e Compare May 8, 2020 17:00
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@affeldt-aist
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@ybertot : it is not yet up to mathcomp standards but here is a tentative proof for your information

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TODO: Hardy's theorem (the true converse of Cesaro)...

Definitions:
- `[sequence E]_n` is a special notation for `fun n => E`
- `series u_` is the sequence of partial sums
- `[normed S]` is the series of absolute values, if S is a series
- `harmonic` is the name of a sequence, apply `series` to them to get the series.

Example: `cvg [normed series (geometric a z)]`
  states the absolute convergence of the series \sum_(n > 0) |a z^n|.

Theorems:
- lots of helper lemmas to prove convergence of sequences
- convergence of harmonic sequence
- convergence of a series implies convergence of a sequence
- absolute convergence implies convergence of series

Co-Authored-By: Cyril Cohen <cyril.cohen@inria.fr>
@affeldt-aist affeldt-aist changed the title A few lemmas about sequences Basic lemmas about sequences May 21, 2020
@CohenCyril CohenCyril merged commit b318306 into master May 23, 2020
@affeldt-aist affeldt-aist deleted the mathcomp_master_sequences branch June 11, 2020 15:44
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