unite SCARD and LLEN

[Birukoff]

I think these two command should be united as 'LEN'. There is nothing
in them or in the underlying data types that makes the current
distinction somehow useful.

[Salvatore Sanfilippo]

Hello birukoff,

but then LEN should also be able to tell the total bytes into a string
value right?
So you end with LEN being a polymorphic version of:

LLEN, SCARD, ZCARD, STRLEN (that currently does not exist)

This appears to be nice if you think at it as a programming language.
With a database what happens is that for a bug you can LEN against a
type you think it's a Set, but for some inconsistency in the dataset
it's actually a String or a List. The program instead to stop
continues to run corrupting the dataset even more.

In calling the right command for the right type there is a bit more
information associated with the command, that will prevent some bug,
and will make the programs more obvious to read.

Cheers,
Salvatore

--
Salvatore 'antirez' Sanfilippo
http://invece.org

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