Ruby - Functional Patterns in Ruby
Which method chain correctly creates a lazy enumerator that selects even numbers from 1 to 10?
Which method chain correctly creates a lazy enumerator that selects even numbers from 1 to 10?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Identify correct lazy usage
Calling.lazyfirst creates a lazy enumerator, then.select(&:even?)filters even numbers lazily.Step 2: Analyze other options
Options B and D call.lazyafter filtering or mapping, which returns an Enumerator but not lazy from the start. (1..10).lazy.map(&:even?) maps to booleans, not selects even numbers.Final Answer:
(1..10).lazy.select(&:even?) -> Option BQuick Check:
Lazy enumerator with select = (1..10).lazy.select(&:even?) [OK]
Quick Trick: Call .lazy before filtering to keep laziness [OK]
Common Mistakes:
- Calling .lazy after select/map loses laziness
- Using map instead of select for filtering
- Confusing order of method calls
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