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8.3.2 Usage
- Function: foldt fup fhere tree
The standard multithreaded tree fold.
fup is of type [a] -> a. fhere is of type object -> a.
- Function: foldts fdown fup fhere seed tree
The single-threaded tree fold originally defined in SSAX. See section (sxml ssax), for more information.
- Function: foldts* fdown fup fhere seed tree
A variant of foldts that allows pre-order tree rewrites. Originally defined in Andy Wingo’s 2007 paper, Applications of fold to XML transformation.
- Function: fold-values proc list . seeds
A variant of fold that allows multi-valued seeds. Note that the order of the arguments differs from that of
fold
.
- Function: foldts*-values fdown fup fhere tree . seeds
A variant of foldts* that allows multi-valued seeds. Originally defined in Andy Wingo’s 2007 paper, Applications of fold to XML transformation.
- Function: fold-layout tree bindings params layout stylesheet
A traversal combinator in the spirit of SSAX’s pre-post-order.
fold-layout
was originally presented in Andy Wingo’s 2007 paper, Applications of fold to XML transformation.bindings := (<binding>...) binding := (<tag> <bandler-pair>...) | (*default* . <post-handler>) | (*text* . <text-handler>) tag := <symbol> handler-pair := (pre-layout . <pre-layout-handler>) | (post . <post-handler>) | (bindings . <bindings>) | (pre . <pre-handler>) | (macro . <macro-handler>)
- pre-layout-handler
A function of three arguments:
- kids
the kids of the current node, before traversal
- params
the params of the current node
- layout
the layout coming into this node
pre-layout-handler is expected to use this information to return a layout to pass to the kids. The default implementation returns the layout given in the arguments.
- post-handler
A function of five arguments:
- tag
the current tag being processed
- params
the params of the current node
- layout
the layout coming into the current node, before any kids were processed
- klayout
the layout after processing all of the children
- kids
the already-processed child nodes
post-handler should return two values, the layout to pass to the next node and the final tree.
- text-handler
text-handler is a function of three arguments:
- text
the string
- params
the current params
- layout
the current layout
text-handler should return two values, the layout to pass to the next node and the value to which the string should transform.
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