Definition of = vs. <-

NOTA BENE: This email is about `=`, the assignment operator (e.g. {a=1}
which is equivalent to { `=`(a,1) } ), not `=` the named-argument syntax
(e.g. f(a=1), which is equivalent to
eval(structure(quote(f(1)),names=c('','a'))).

As far as I can tell from the documentation, assignment with = is precisely
equivalent to assignment with <-.  Yet they call different primitives:

`=`

.Primitive("=")

`<-`

.Primitive("<-")

(Perhaps these are different names for the same internal function?)

Also, the difference is preserved by the parser:

quote({a=b})

{
    a = b
}

quote({a<-b})

{
    a <- b
}

even though in other cases the parser canonicalizes variant syntax, e.g. ->
to <-:

quote({a->b})

{
    b <- a
}

`->`

Error: object "->" not found

Is there in fact some semantic difference between = and <- ?

If not, why do they use a different operator internally, each calling a
different primitive?

Or is this all just accidental inconsistency resulting from the '=', '<-',
and '->' features being added at different times by different people working
off different stylistic conventions?

            -s

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