Step 3 / Select topic Go Hard

What this bank covers

• Go integer division, remainder, and right shift with negatives
• Complex types: untyped constants, complex/real/imag, complex64
• Go: int8 overflow in / -1, negation, and signed vs unsigned shifts
• Cutset trimming versus literal prefix trimming
• Mixing a typed operand with an untyped constant
• Unary complement combined with AND NOT
• Sized integer operands: shifts, truncated division and wraparound
• Lexicographic byte-wise string comparison
• Ring.Unlink when n is a multiple of the length
• Go binary operator precedence
• Integer division and remainder signs
• AND NOT (&^) versus XOR (^)
• Untyped constants versus float32 precision
• Constant vs float64 arithmetic
• Five ways to round -2.5
• Truncating integer conversions
• The 2^53 gap in float64
• Bit counting helpers
• QuoRem versus DivMod
• Negative zero in float64
• Shift counts and width
• Round-half-to-even in fmt
• len counts bytes, not characters
• Split edge cases: empty separator and empty input
• ToUpper applies simple case mapping only
• Index results are byte offsets, and empty substrings are special
• Count with an empty substring counts rune boundaries
• EqualFold uses Unicode simple folding
• Fields collapses whitespace runs, Split does not
• Range expression is evaluated once
• Ranging over an array copies it
• Range over string yields byte index and rune
• Range over an integer
• Range over func and the yield protocol
• maps.Keys/Values return iterators
• Ranging over a closed channel
• Per-iteration loop variables
• Ranging over nil maps and slices
• Range over a pointer to array is not always evaluated
• Full slice expressions cap the reslice
• copy handles overlapping slices
• NaN keys in a Go map
• Doubly linked list reordering
• Two appends to one spare slot
• Missing keys, zero values, and delete
• Less decides heap orientation
• Arrays are comparable map keys
• Reads and writes on a nil map
• Deferred functions can modify named results only
• Implicit blocks in if and switch create nested scopes
• Defer argument evaluation time versus closure capture
• recover only works when called directly by a deferred function
• Method values bind the receiver when they are evaluated
• A variadic parameter can be nil or empty-but-non-nil
• Package variables initialize by dependency, init funcs in source order
• Recovering inside a defer can rewrite named results
• Function operands are evaluated in lexical left-to-right order
• Defer is scoped to the function, not the enclosing block
• Typed nil stored in an error interface
• Defer order during panicking and recovery
• sync.Once treats a panicking f as done
• A nil channel case is never ready
• close drains, it does not discard
• len and cap of a closed buffered channel
• Cancellation propagates to derived contexts
• A closed channel is always ready to receive
• CancelFunc is idempotent
• sync.Map LoadOrStore returns the existing value
• A WaitGroup counter must never go negative
• Disabling select cases by setting channels to nil
• Preallocation only avoids growth while capacity lasts
• Field ordering changes struct size because of alignment padding
• slices.Clip drops unused capacity
• string(b) as a map key copies the bytes
• slices.Grow reserves capacity without changing length
• copy is bounded by length, not capacity
• Spare capacity makes independent appends alias
• Reset semantics differ for Builder and Buffer
• Signed division is not a plain arithmetic shift
• iota counts lines, implicit repetition reuses the expression
• Converting a rune encodes UTF-8; converting a byte slice copies raw bytes
• A typed nil pointer stored in an interface is not nil
• Range copies elements; index to mutate them
• fallthrough ignores the next case's condition, and default is tried last
• Tuple assignment evaluates index operands before assigning
• Embedding promotes methods but gives no virtual dispatch
• case nil matches an empty interface; multi-type cases keep the original static type
• Labeled continue restarts the outer loop; labeled break exits it
• Interface comparison can panic on uncomparable dynamic types
• strings.Map and the negative sentinel
• strings.Cut when the separator is missing
• %w versus %v in fmt.Errorf
• errors.Join and multi-error unwrapping
• errors.As target assignment
• Panicking inside a deferred function
• break inside a switch inside a loop
• goto as a backward loop
• errors.Is honours a custom Is method
• Strength reduction on signed remainder
• Multiple %w verbs: Unwrap() []error vs errors.Unwrap