Step 3 / Select topic Ruby Medium

What this bank covers

• Ruby `*` is receiver-dependent
• Proc vs lambda: argument binding and return
• Ruby truthiness
• Integer vs Float division
• Integer division and modulo in Ruby
• The spaceship operator and incomparable types
• == versus eql? for numbers
• Integer division truncates the remainder
• Integer division floors toward negative infinity
• Ruby's % takes the sign of the divisor
• Floats are binary approximations
• Rounding with negative digits
• to_i truncates, floor and ceil go in fixed directions
• Float division by zero
• Math.sqrt versus Integer.sqrt
• Rational arithmetic is exact and normalised
• Float#round and the half: option
• sub replaces only the first match
• Plain string literals are mutable by default
• String#* repeats the string
• split keeps interior empty fields
• Bang string methods return nil when nothing changes
• Single quotes do not interpolate
• center pads both sides
• Negative start index with a length
• tr translates characters positionally
• String#tr character translation
• each_with_object returns the memo object
• with_index accepts a starting offset
• Lazy enumerators work on infinite sequences
• Enumerable builds everything on top of each
• zip pads with nil using the receiver's length
• each_cons yields overlapping windows
• chunk_while groups by comparing neighbours
• External iteration with Enumerator#next and #rewind
• Enumerable is built on a single each method
• each_slice returns an Enumerator of fixed-size groups
• Hash.new(0) as a counter
• The shared default object trap
• Array as both stack and queue
• Array#delete removes every match
• Set union, intersection and difference
• String keys are duplicated and frozen
• flatten with and without a depth limit
• Binary search in find-minimum mode
• Reversing a linked list built from Struct nodes
• Ruby hashes keep insertion order
• Default arguments see earlier parameters
• def is a scope gate
• Block-local variables with the semicolon list
• Splat, keyword, and double-splat parameters
• define_method closes over the enclosing scope
• Lambdas sharing a captured local variable
• return inside a block exits the enclosing method
• Optional blocks, yield, and &:symbol
• ensure does not change the return value
• An explicit return inside ensure wins
• retry restarts the begin block
• Bare rescue only catches StandardError
• throw/catch for non-local exit
• Rescue clauses are matched top to bottom
• next supplies the block's value
• loop rescues StopIteration
• The inline rescue modifier
• Unwinding order of nested ensure and rescue
• Mutex#synchronize protecting a shared counter
• Exceptions escaping a thread
• Queue as a thread-safe FIFO channel
• Ruby's Mutex is not reentrant
• Fiber resume and Fiber.yield interleaving
• Thread#status for a normally terminated thread
• Thread#value joins and returns the block result
• Thread.current[] is per-thread storage
• Closing a Queue drains then returns nil
• Values flow both ways through Fiber.yield
• In-place append vs. reassignment
• The nil pitfall in ||= memoization
• Array#include? is O(n)
• Lazy enumerators do only the work you consume
• flat_map avoids the intermediate array
• Integer#pow with a modulus
• sort_by computes each key once
• Range#bsearch is logarithmic
• Memoizing recursion with a Hash default block
• String += allocates, << mutates in place
• Array.new with a default value shares one object
• Hash.new(default) returns a shared, unstored default
• `and` has lower precedence than assignment
• String#succ carries across letter and digit classes
• Exponentiation precedence and associativity
• Array.new default value versus block
• Splats in multiple assignment
• Spaceship operator with incomparable types
• === is not symmetric
• != is derived from ==
• Result types of numeric operators
• prepend places a module before the class in the ancestor chain
• Array#* dispatches on argument type
• Method bodies open a new local scope
• Ruby format flags: zero-pad, forced sign, hex