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37 lines
854 B
37 lines
854 B
package main
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import "fmt"
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// ErrEmpty denotes an empty stack
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var ErrEmpty = fmt.Errorf("stack empty")
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// ErrUnderflow denotes a PICK that tried to pick a value that didn't exist
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var ErrUnderflow = fmt.Errorf("cannot pick value from beyond stack depth")
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// Stack is a stack of integers with no defined max depth
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type Stack struct {
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values []int
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}
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// Pop returns the top of the stack
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func (s *Stack) Pop() (int, error) {
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if len(s.values) == 0 {
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return 0, ErrEmpty
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}
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i := s.values[0]
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s.values = s.values[1:]
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return i, nil
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}
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// Push adds a value to the top of the stack
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func (s *Stack) Push(i int) {
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s.values = append([]int{i}, s.values...)
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}
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// Pick grabs a value from the given depth in the stack, non-destructively.
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func (s *Stack) Pick(i int) (int, error) {
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if len(s.values) <= i {
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return 0, ErrUnderflow
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}
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return s.values[i], nil
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}
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