github.com/wzzhu/tensor@v0.9.24/slice.go (about)

     1  package tensor
     2  
     3  // A Slice represents a slicing operation for a Tensor.
     4  type Slice interface {
     5  	Start() int
     6  	End() int
     7  	Step() int
     8  }
     9  
    10  type rs struct {
    11  	start, end, step int
    12  }
    13  
    14  func (s rs) Start() int { return s.start }
    15  func (s rs) End() int   { return s.end }
    16  func (s rs) Step() int  { return s.step }
    17  
    18  // makeRS creates a ranged slice. It takes an optional step param.
    19  func makeRS(start, end int, opts ...int) rs {
    20  	step := 1
    21  	if len(opts) > 0 {
    22  		step = opts[0]
    23  	}
    24  	return rs{
    25  		start: start,
    26  		end:   end,
    27  		step:  step,
    28  	}
    29  }
    30  
    31  // ss is a single slice, representing this: [start:start+1:0]
    32  type ss int
    33  
    34  func (s ss) Start() int { return int(s) }
    35  func (s ss) End() int   { return int(s) + 1 }
    36  func (s ss) Step() int  { return 0 }
    37  
    38  // sli is slice. It's named sli to prevent confusion over naming
    39  type sli struct {
    40  	start, end, step int
    41  }
    42  
    43  // S creates a Slice.
    44  // end is optional. It should be passed in as the first param of the optionals.
    45  // step is optional. It should be passed in as the second param of the optionals.
    46  //
    47  // Default end is start+1. Default step is 1, unless end == step+1, then it defaults to 0
    48  func S(start int, opt ...int) Slice {
    49  	var end, step int
    50  	if len(opt) > 0 {
    51  		end = opt[0]
    52  	} else {
    53  		end = start + 1
    54  	}
    55  
    56  	step = 1
    57  	if len(opt) > 1 {
    58  		step = opt[1]
    59  	} else if end == start+1 {
    60  		step = 0
    61  	}
    62  
    63  	return &sli{
    64  		start: start,
    65  		end:   end,
    66  		step:  step,
    67  	}
    68  }
    69  
    70  func (s *sli) Start() int { return s.start }
    71  func (s *sli) End() int   { return s.end }
    72  func (s *sli) Step() int  { return s.step }