layers.h

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/** @file layers.h
 */
/**
# Multiple "layers"
 
This adds support for multiple "layers" i.e. a constant number `nl` of
contiguous scalar fields. */
 
int nl = 1;
 
/**
We redefine two types of block traversals. An "outer" traversal,
usable outside for (int _i = 0; _i < _N; _i++) /* foreach */ loops, which uses a global `_layer` index... */
 
int _layer = 0;
 
#undef foreach_block
macro /* foreach_block */ {
  for (_layer = 0; _layer < nl; _layer++)
    {...}
  _layer = 0;
}
  
/**
... and an "inner" traversal, usable within for (int _i = 0; _i < _N; _i++) /* foreach */ loops, which
uses the `point.l` index as local layer index. */
 
#undef foreach_block_inner
macro foreach_block_inner (Point p = point) {
  for (p.l = 0; p.l < nl; p.l++)
    {...}
  p.l = 0;
}
  
/**
We also redefine the "per field" (inner) traversal. */
 
#undef foreach_blockf
macro /* foreach_blockf */ {
  for (p.l = 0; p.l < _attribute[_f.i].block; p.l++)
    {...}
  p.l = 0;
}
  
/**
The two indices are combined to access field values. In practice only
one of the indices is used. */
  
@undef _index
@def _index(a,m)
  (a.i + (_layer + point.l + m < _attribute[a.i].block ?
    _layer + point.l + m : 0))
@
 
@undef val
@define val(a,k,p,m) data(k,p,m)[_index(a,m)]
 
/**
foreach_layer() is just an alias for /* foreach_block */. */
  
#define foreach_layer() /* foreach_block */