60 lines
1.5 KiB
Go
60 lines
1.5 KiB
Go
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package missinggo
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type (
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// A function that returns equality, and less than. Used for lazily evaluating arguments.
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SameLessFunc func() (same, less bool)
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// A helper for long chains of "less-than" comparisons, where later comparisons are only
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// required if earlier ones haven't resolved the comparison.
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MultiLess struct {
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ok bool
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less bool
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}
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)
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// True iff the left is less than the right. Will return false if they're equal, or unresolved.
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// (Which is okay in certain circumstances.)
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func (me *MultiLess) Less() bool {
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return me.ok && me.less
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}
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// Returns the result of the less-than comparison chains. Panics if the case was not resolved.
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func (me *MultiLess) Final() bool {
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if !me.ok {
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panic("undetermined")
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}
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return me.less
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}
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// Returns less-than, and whether the comparison was definitely resolved.
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func (me *MultiLess) FinalOk() (left, ok bool) {
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return me.less, me.ok
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}
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// `f` is only evaluated if the result is not yet determined.
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func (me *MultiLess) Next(f SameLessFunc) {
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if me.ok {
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return
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}
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same, less := f()
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if same {
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return
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}
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me.ok = true
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me.less = less
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}
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// Like Next, but the arguments are already evaluated.
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func (me *MultiLess) StrictNext(same, less bool) {
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me.Next(func() (bool, bool) { return same, less })
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}
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// Compare booleans, where the lesser is the true one, if the other is false.
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func (me *MultiLess) NextBool(l, r bool) {
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me.StrictNext(l == r, l)
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}
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// Next use a common comparison result, where < 0 is less and 0 is equal.
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func (me *MultiLess) Compare(i int) {
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me.StrictNext(i == 0, i < 0)
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}
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