Fixes and better loops

[wheeheee]

• redundant exp log?
• fixed some typos
• throw named errors
• loops run faster
• some memoization?

[coveralls]

Pull Request Test Coverage Report for Build 6676470376

• 96 of 201 (47.76%) changed or added relevant lines in 4 files are covered.
• 3 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+10.7%) to 54.435%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/feacalc.jl	23	32	71.88%
src/mfccs.jl	29	57	50.88%
src/rasta.jl	37	105	35.24%
<!--	Total:	96	201	47.76%	-->

Files with Coverage Reduction	New Missed Lines	%
src/feacalc.jl	1	45.61%
src/mfccs.jl	1	58.62%
src/rasta.jl	1	49.1%
<!--	Total:	3		-->

Totals
Change from base Build 6610274851:	10.7%
Covered Lines:	270
Relevant Lines:	496

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💛 - Coveralls

[davidavdav]

Thanks, I went through the diffs (in reverse order), and it looks like a pretty thorough re-write!

[wheeheee]

Actually I was a little confused by the code in deltas so do you mind confirming that it keeps only rows 2hlen+1 onwards? Since you've padded hlen rows in front and behind, I thought the middle would be kept after filt, but I don't really get what filt does.