Step 3 / Select topic Ruby Hard

What this bank covers

• Module comparison operators (<, <=, >, <=>)
• Ruby equality: ==, eql?, === and <=> across numeric types
• Spaceship operator and incomparable types
• Floored division, modulo, and remainder
• Integer exponentiation with a negative exponent
• Assignment binds tighter than `or`
• Precedence and associativity of **
• Numeric coercion across Integer, Rational, and Float
• Integer#divmod with a negative dividend
• Exact Rational addition and normalization
• Integer.sqrt gives the exact floor of a square root
• Array#sum uses compensated summation for Floats
• NaN equality versus Array#include?
• Integer#round with negative digits and the half: option
• Integer#to_s and String#to_i with explicit bases
• truncate, floor, and round on a negative half
• Integer#pow with a modulus
• Deduplicated frozen strings with -@
• String slicing at and past the end
• String#succ carry rules
• gsub with a hash replacement
• split limits, awk mode, and empty separators
• << mutates, += rebinds
• dup, clone, and +@ on a frozen string
• String#% format directives
• String#tr with character ranges
• chunk_while groups consecutive runs
• each_with_object discards the block's return value
• Lazy chains pull only what is needed
• zip with a block returns nil
• peek does not advance an Enumerator
• group_by keys follow first-seen order
• flat_map flattens exactly one level
• Counting block invocations in a lazy filter
• cycle without a block returns an endless Enumerator
• Enumerable builds on a single each method
• Hash.new with a mutable default object
• Array.new default value vs block form
• Mutating a hash key requires rehash
• Hash#[]= duplicates and freezes String keys
• Struct value semantics as hash keys
• Deleting from an array while iterating it
• Hash insertion order after delete and reassignment
• Shallow dup vs Marshal deep copy
• dup vs clone and frozen state
• Set equality and hashing ignore insertion order
• A nested def defines a method on the enclosing class
• Block-local variable declarations
• Local variables are created at parse time
• Default arguments see earlier parameters
• `return` inside a non-lambda proc
• define_method closes over locals, `def` does not
• Hash literals are positional in Ruby 3
• Bindings know every local of the scope
• `for` does not create a new scope, blocks do
• Orphaned proc with `return`
• Explicit return inside ensure
• retry restarts the begin body
• Bare rescue only catches StandardError
• throw unwinds to catch with a value
• next supplies a block's value
• break returns from the yielding method
• Kernel#loop rescues StopIteration
• An exception from ensure replaces the original
• Automatic exception cause chaining
• Exceptions raised in an else clause skip their own rescue
• Fiber-local vs thread-local variables
• Popping from a closed Queue
• Thread#status after termination
• Values passed through Fiber.yield and resume
• Mutex#synchronize, owned? and locked?
• Thread#join return value with a timeout
• ConditionVariable#wait releases the mutex
• SizedQueue blocks producers until space frees up
• Thread#kill still unwinds ensure clauses
• Memoization with ||= and falsy results
• Array#sum uses compensated summation
• << mutates in place, += reallocates
• Lazy enumerators pull only what is needed
• sort_by is a Schwartzian transform
• bsearch is logarithmic in the array length
• Hash default proc as a memo table
• inject threads the block's return value, each_with_object does not
• String#-@ deduplicates, String#+@ unfreezes
• The `||=` memoization hole for falsy values
• Module#prepend inserts the module before the class
• Find patterns match the leftmost occurrence
• compare_by_identity keys on object identity
• Protected methods and respond_to?
• Currying a non-lambda proc
• Lexical scope wins over inheritance for constants
• Comparable and a nil spaceship result
• dup versus clone and singleton methods
• Float#to_r versus Float#rationalize
• squeeze, delete, and count share one character-set notation
• Thread status after an uncaught exception
• Endianness modifiers in pack and unpack
• Singleton class ancestry with extend and prepend
• Bitwise operators on negative Integers
• Value of an assignment expression with a custom []=