This compiles|runs using `loop do ...`

versus `(2..).each do |pow|`

.

WHY?

They are **functionally** equivalent (to a user), but obviously not to the compiler.

```
def palindromegen(digit, count)
nums = [] of UInt64
nn = digit * 11
num = 0.to_u64
pow = 1
loop do pow += 1 # replaces: (2..).each do |pow|
base = 10_u64**(pow >> 1)
n1 = base * digit
n2 = base * (digit + 1)
n1.step(to: n2 - 1, by: 10) do |n1|
ns = (n1 // 10).to_s
(n1..n1 + 9).each_with_index do |pal, i|
num = (pal.to_s + pal.to_s.reverse).to_u64 if pow.odd?
num = (ns + "0" + ns.reverse).to_u64 + base * i if pow.even?
nums << num if num % nn == 0
return nums if nums.size == count
end
end
end
end
count = 20
puts "First 20 palindromic gapful numbers 100 ending with:"
(1..9).each { |digit| print "#{digit} : #{palindromegen(digit, count)}\n" }
count = 100
puts "\nLast 15 of first 100 palindromic gapful numbers ending in:"
(1..9).each { |digit| print "#{digit} : #{palindromegen(digit, count).last(15)}\n"
```

This also compiles|runs using `(2..).select do |pow|`

```
def palindromegen(digit, count)
nums = [] of UInt64
nn = digit * 11
num = 0.to_u64
(2..).select do |pow|
base = 10_u64**(pow >> 1)
n1 = base * digit
n2 = base * (digit + 1)
n1.step(to: n2 - 1, by: 10) do |n1|
ns = (n1 // 10).to_s
(n1..n1 + 9).each_with_index do |pal, i|
num = (pal.to_s + pal.to_s.reverse).to_u64 if pow.odd?
num = (ns + "0" + ns.reverse).to_u64 + base * i if pow.even?
nums << num if num % nn == 0
return nums if nums.size == count
end
end
end
end
```

This also works.

```
def palindromegen(digit, count)
nums = [] of UInt64
nn = digit * 11
num = 0.to_u64
pow = 1
while true
pow += 1
base = 10_u64**(pow >> 1)
n1 = base * digit
n2 = base * (digit + 1)
n1.step(to: n2 - 1, by: 10) do |n1|
ns = (n1 // 10).to_s
(n1..n1 + 9).each_with_index do |pal, i|
num = (pal.to_s + pal.to_s.reverse).to_u64 if pow.odd?
num = (ns + "0" + ns.reverse).to_u64 + base * i if pow.even?
nums << num if num % nn == 0
return nums if nums.size == count
end
end
end
end
```

So there’s something intrinsically different to the compiler about `(2..).each`

.