Step 3 / Select topic Ruby Easy

What this bank covers

• Integer vs Float division in Ruby
• `and`/`or` bind looser than `=`
• Integer#gcd
• Math.sqrt always returns a Float
• Summing a Range
• Integer.sqrt
• map transforms every element
• tally counts occurrences in first-seen order
• select keeps the matching elements
• take_while stops at the first failure
• sort_by orders by a computed key
• Range#step walks the range in increments
• each_with_index yields element then index
• Maximizing with max_by
• minmax returns both extremes
• min_by for the closest value
• Taking the top N with max(n)
• sort.first versus min
• Memoizing with ||=
• String keys vs Symbol keys
• Strings are shared by reference
• Strings compare character by character
• String#% as a format operator
• Numeric == compares mathematical value
• Array as a stack: push and pop
• Array as a queue: shift takes the front element
• Hash#fetch with a default value
• Hash#dig through nested hashes and arrays
• Set discards duplicate values
• Hash keys come back in insertion order
• Default parameter values
• Methods do not see surrounding locals
• retry restarts the begin body
• next and break inside a while loop
• rescue matches subclasses of the named class
• Thread#value returns the block's result
• Thread::Queue is FIFO
• Fiber.yield and resume
• Thread.current vs Thread.main
• Queue#pop, #size and #empty?
• String#swapcase
• String#split keeps interior empty fields
• start_with? is case-sensitive
• String#strip
• String#gsub replaces all matches
• String#sub replaces one match
• Substring by start and length
• String#+ concatenates
• String#count
• Keyword arguments with defaults
• block_given? and yield
• Lambdas close over local variables
• rescue and ensure order in a method body
• begin/rescue/else/ensure
• Only nil and false are falsy in Ruby
• Floats cannot represent 0.1 exactly
• ensure runs even on an explicit return
• A bare raise re-raises the current exception
• Exponentiation is right-associative
• Integer vs float division
• The spaceship operator
• && returns an operand, not a boolean
• Integer#divmod
• Comparable#clamp
• Modulo with a negative dividend
• String#capitalize
• Enumerable#each_slice
• Array#zip with a shorter argument
• Enumerator::Lazy
• Array#flatten with a depth limit
• Array#rotate
• Array#insert with multiple values
• Keyword arguments with default values
• Block-local variables declared after a semicolon
• Default argument values can reference earlier parameters
• case/when with ranges
• ensure runs with or without an exception
• The class of a rescued exception
• Collecting results from several threads
• Guarding a shared counter with a Mutex
• Fiber resume values and alive?
• Closing a Thread::Queue
• Hash.new(0) for counters
• Range#bsearch in find-minimum mode
• find stops at the first match
• Set vs Array membership tests
• Assigning past the end of an Array
• Hash defaults do not create keys
• <=> returns nil for incomparable operands
• Array#uniq keeps first occurrences
• Thread state after join