ruby - using each and map to modify a range of an array indices -

the following code:

a = [1,2,3,4,5] b = a.each.map {|i| = 0}  # or   b = a.map {|i| = 0}  same thing

makes b = [0, 0, 0, 0, 0] expected

is there equally succinct way change range of a? (ex: set a[2..4] 0)

i have messed around in irb, code returns elements modified

a = [1,2,3,4,5] b = a[2..4].each.map {|i| = 0}

makes b = [0, 0, 0], trying make b = [1, 2, 0, 0, 0]

i'm not sure trying here.

first: why turning array enumerator , map enumerator instead of mapping array directly? i.e. why have

b = a.each.map {|i| = 0 }

instead of

b = a.map {|i| = 0 }

also, why assigning block local variable i never using variable? i.e. why don't

b = a.map {|i| 0 }

of course, aren't using i at all ...

b = a.map { 0 }

however, since values of b have absolutely no relationship @ values of a, might

b = [0] * a.size

the same questions apply second code example. again, ignore elements of a, using map makes no sense whatsoever. can

(b = a.dup)[2..4] = [0] * 3

or more readable broken 2 expressions

b = a.dup b[2..4] = [0] * 3 # or ... = [0, 0, 0]

Barbera