Add a general shuffler and deck shuffling.
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@ -23,7 +23,7 @@ const (
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// The Deck stores cards yet-to-be-dealt.
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type Deck[C StatsCollection] struct {
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cards []Card[C]
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rand rand.Rand
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rand *rand.Rand
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}
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// Len returns the number of cards in the Deck.
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@ -196,3 +196,45 @@ func (d *Deck[C]) InsertRandomRange(loFrac, hiFrac float64, card Card[C]) error
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errs.Add(d.Insert(slot, card))
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return errs.Emit()
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}
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// Shuffle completely shuffles the deck. If the deck has one or fewer cards,
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// this returns WarningTooFewCards since nothing can be shuffled.
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func (d *Deck[C]) Shuffle() error {
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if len(d.cards) < 2 {
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return WarningTooFewCards
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}
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ShuffleAll(d.cards, d.rand)
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return nil
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}
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// ShufflePart shuffles the `n` cards of the deck starting at `loc`.
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// If the provided range doesn't fit in the deck, this returns
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// WarningTopClamped and/or WarningBottomClamped. If the eventual range
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// of cards to be shuffled (after any off-the-end issues are corrected)
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// is one or less, this returns WarningTooFewCards since nothing can
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// be shuffled.
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func (d *Deck[C]) ShufflePart(loc, n int) error {
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if n < 2 {
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// Nothing to do.
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return WarningTooFewCards
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}
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var errs ErrorCollector
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if loc < 0 {
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errs.Add(Warningf("%w: loc was %d", WarningTopClamped, loc))
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loc = 0
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}
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if loc+n > d.Len() {
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errs.Add(Warningf("%w: deck size %d does not have %d cards at and after location %d",
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WarningBottomClamped, len(d.cards), n, loc))
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n = d.Len() - loc
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// Now is there anything to do?
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if n < 2 {
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errs.Add(WarningTooFewCards)
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return errs.Emit()
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}
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}
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ShufflePart(d.cards, d.rand, loc, n)
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return nil
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}
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@ -2,6 +2,7 @@ package cardsim
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import (
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"fmt"
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"math/rand"
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)
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// InsertInto inserts one or more items into a slice at an arbitrary index.
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@ -98,3 +99,30 @@ func DeleteNFrom[T any](slice []T, loc, n int) []T {
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copy(slice[loc:], slice[loc+n:])
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return slice[:len(slice)-n]
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}
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// ShuffleAll shuffles everything in slice, using the provided rand.Rand.
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// If no rand.Rand is provided, this uses the default source.
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func ShuffleAll[T any](slice []T, r *rand.Rand) {
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shuffle := rand.Shuffle
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if r != nil {
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shuffle = r.Shuffle
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}
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shuffle(len(slice), func(i, j int) {
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slice[i], slice[j] = slice[j], slice[i]
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})
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}
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// ShufflePart shuffles the `n` elements of `slice` starting at `loc`
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// in-place, using the provided rand.Rand. If the range of items to
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// shuffle is not entirely within `slice`, this panics.
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//
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// If no rand.Rand is provided, this uses the default source.
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func ShufflePart[T any](slice []T, r *rand.Rand, loc, n int) {
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if loc < 0 || loc+n > len(slice) {
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panic(fmt.Sprintf("can't shuffle %d elements from a %d-element slice at location %d", n, len(slice), loc))
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}
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if n < 1 {
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return
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}
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ShuffleAll(slice[loc:loc+n], r)
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}
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