#! /usr/bin/python3

typedef enum
  { ix_reduction_SINGLE,  # ... *,*,*,0,1,2,3,4,5,*,*,*,*,*,*,*,*,*,* ...
    ix_reduction_EXTEND,  # ... 0,0,0,0,1,2,3,4,5,5,5,5,5,5,5,5,5,5,5 ...
    ix_reduction_REPEAT,  # ... 3,4,5,0,1,2,3,4,5,0,1,2,3,4,5,0,1,2,3 ...
    ix_reduction_MIRROR,  # ... 2,1,0,0,1,2,3,4,5,5,4,3,2,1,0,0,1,2,3 ...
    ix_reduction_PXMIRR   # ... 3,2,1,0,1,2,3,4,5,4,3,2,1,0,1,2,3,4,5 ...
  } ix_reduction_t;
#define ix_reduction_FIRST ix_reduction_SINGLE
#define ix_reduction_LAST  ix_reduction_PXMIRR
  # A mapping from unrestricted {ix_index_t} values (positive or negative) to
  # integers in some range {0..N-1}.  The comments above illustrate each mapping
  # for {N=6} and various indices from {-3} to {+15}.  The code '*' denotes {-1}.

# ELEMENT INDEXING

ix_index_t ix_reduce ( ix_index_t i, ix_size_t N, ix_reduction_t red );
  # Returns the index {i} reduced to {0..N-1} as specified by {red}

void ix_reduce_range ( ix_index_t i0, ix_size_t m, ix_size_t N, ix_reduction_t red, ix_index_t i[] );
  # Stores into {i[0..m-1]} the indices {i0..i0+m-1} reduced to {0..N-1} as specified by {red}.