#129 Loops

All the various ways of looping in Ruby.

Notes

for..in

The basic for <variable> in <enumerable> <block> structure is common, especially when iterating aribitrary ranges.

See ruby doc: for loop

each

When needing to iterate all items in a collection, the <enumerable>.each <block> structure is generally preferred.

See ruby doc: Array#each

while

The while <condition> <block> structure is ideal for when the condition needs to be checked before any iteration.

See ruby doc: while loop

Until

The until <condition> <block> structure is similar to while except uses the complimentay condition. The condition is checked before the block is executed.

See ruby doc: until loop

Loop

The loop syntax is a shortcut for an infinite while true <block> loop. A break condition would be used to exit the loop. See ruby doc: break

loop do
  ...
  break if <cond>
end

Unless/While Modifiers

An old, now discouraged (Re: semenatics of if/unless/while statement modifiers) syntax is to apply a while/until modifier to a block.

ruby doc: while/until modifiers

Why discouraged? .. because it’s hard for users to tell

begin end while

works differently from

while

Running the Examples

See examples.rb; these demonstrations are written asa test suite:

$ ruby examples.rb
Run options: --seed 8730

# Running:

...........

Finished in 0.001201s, 9159.0354 runs/s, 9159.0354 assertions/s.

11 runs, 11 assertions, 0 failures, 0 errors, 0 skips

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