A slice defines a sub-range or patch of a dimension. More...

#include <slice.h>

Public Member Functions
	Slice ()

	Slice (long s, long e, long stp=1)

Slice &	operator= (const Slice &s)

Public Attributes
long	start

long	end

long	step

Detailed Description

A slice defines a sub-range or patch of a dimension.

Introduction

The slice Slice(start,end,step) defines the subvector

[start, start+step, start+2*step, ..., end]

with indices as if generated from these loops

if (step > 0) 
    for (i=start; i<=end; i+=step) i;
else if (step < 0) 
    for (i=start; i>=end; i+=step) i;
else if (step == 0  && start == end) 
    defines a scalar
else 
    runtime error detected when slice is used

Note that start and end are inclusive, unlike the Python convention of specifying end+1 (note that we cannot do this easily in C/C++ unless we also define a special value to indicate the end of a dimension of unknown size).

Special meanings and conventions

Negative values for start or end (similar to Python) are relative to the end of the (possibly unknown) dimension. E.g.,

end=-1 is equivalent to end=dim-1
start=-4 is equivalent to start=dim-4
step=0 and start==end implies dimension will be eliminated when the slice is used to index a tensor
The default constructor specifies the entire dimension
If the input length is not an exact multiple of step, end is rounded towards start to recover the behaviour of the <= or >= bounds in the loops specified above.

Special slices have been defined as constants

_ (1 underscore) = Slice(0,-1,1) = full slice in current order
___ (3 underscores) = Array of Slices with value _ so that t(___) will generate an assignable view of the entire tensor t .
_reverse = Slice(-1,0,-1) = full dimension reversed