CSVediting.md

@@ -157,10 +157,22 @@ parameter to the compileRE method of the RE compiler.
     Marker compileRE(RE * re, Marker initialMarkers);
 ```
 If the marker stream returned by the RE_compiler has a one bit anywhere
-within the column, then a match is found.   
+within fields belonging to the column, then a match is found.   
+
+Matches within the fields of the column can then be moved to the field separator position of the column, using the ```MatchedLinesKernel``` as shown above, but substituting the field separator stream in place of ```mLineBreakStream```.
+Call this stream ```FieldMatchMarks```.
+
+Given the ```FieldMatchMarks``` stream, then a mask covering the entire
+field can be produced using logic similar to that for masks selecting rows.
+The first step is to compute a stream ```MatchesByField``` by using the
+```FilterByMask``` function with the field separator stream as the mask and ```FieldMatchMarks``` as the data stream.    The second step is to compute
+a stream marking field starts using the ```LineStartsKernel``` as shown above,
+but again substituting the field separator stream in place of ```mLineBreakStream```.
+The third step is to compute matched field starts used ```SpreadByMask``` with the field starts stream as the mask applied to ```MatchesByField```.   Finally, the mask
+covering matched fields can be computed using the ```LineSpansKernel``` applied
+to the matched field starts and ```FieldMatchMarks```.
 
 ## Combining Masks
 
 If masks are computed to edit out both a column and a row, these can be combined with a Pablo
-createAnd operation and then one FilterByMask can be applied.
-
+createAnd operation and then one FilterByMask can be applied.
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