# HG changeset patch
# User Henry S. Thompson <ht@markup.co.uk>
# Date 1496334105 -3600
# Node ID adeb9575b273602625a9df3a1e68a18991a2ba64
# Parent  a783afa2b1099ba4e9e6271c86dd4f6b67ad9644
add inverted rel pointers back to referencing from referenced

diff -r a783afa2b109 -r adeb9575b273 n2a.xsl
--- a/n2a.xsl	Wed May 31 17:41:18 2017 +0100
+++ b/n2a.xsl	Thu Jun 01 17:21:45 2017 +0100
@@ -45,6 +45,22 @@
                                   then $b/text()
                                  else e:shouldnt('rnf',concat(local-name($b),' ',string($b)))"/>
  </xsl:function>
+
+ <xsl:function name="e:bcrnf" as="xs:string">
+  <!-- Like crnf, but backpointer -->
+  <!-- compute CR-normal-form of a singleton reference -->
+  <xsl:param name="s" as="element(e:s)"/>
+  <xsl:value-of select="concat(e:bnf(($s/*)[1]),e:bnf(($s/*)[2]))"/>
+ </xsl:function>
+ 
+ <xsl:function name="e:bnf" as="xs:string">
+  <!-- invert any relative references, neutralise any absolute ones, i.e. convert a pointer into a kind of backpointer -->
+  <xsl:param name="s" as="element(*)"/><!-- either a(bsolute) or r(elative)-->
+  <xsl:value-of select="if (local-name($s)='a')
+                         then concat('&#xAA;',$s) (: avoid spurious concord :)
+                         else concat('&#xBA;',-xs:integer($s/@d))"/>
+ </xsl:function>
+
  
  <xsl:function name="e:fnf" as="xs:string">
   <!-- rebuild a formula from its parts, but using CRNF for all references -->
diff -r a783afa2b109 -r adeb9575b273 notes.txt
--- a/notes.txt	Wed May 31 17:41:18 2017 +0100
+++ b/notes.txt	Thu Jun 01 17:21:45 2017 +0100
@@ -111,7 +111,10 @@
 Should put another step after refs.xsl to compute a map from
 distinct-values of all targets to all the cells which use them
 DONE.
-Likewise ranges @@
+Now provides inverted rel. ref info so that static input columns can
+be identified from their users.
+
+Likewise ranges --  range endpoints in place, @@ what about the things themselves?
 
 That really does mean we should move to elts for
 each ref or range, since at this point we want to compute vector
@@ -223,8 +226,8 @@
     #F13A13, # Vivid Reddish Orange
     #232C16, # Dark Olive Green
 ------------
-@@ string identify, to say nothing of actual value, is lost -- fix?
-@@ row/column/both spans
+@@ string identity, to say nothing of actual value, is lost -- fix?
+@@ row/column/both spans [what?]
 ------
 enron1k/kenneth_lay__19506 contains this formula:
 
diff -r a783afa2b109 -r adeb9575b273 refs2.xsl
--- a/refs2.xsl	Wed May 31 17:41:18 2017 +0100
+++ b/refs2.xsl	Thu Jun 01 17:21:45 2017 +0100
@@ -23,7 +23,9 @@
    <xsl:variable name="r" select="."/>
    <i r="{$r}">
     <xsl:for-each select="key('ref',$r,$refs)">
-     <r><xsl:value-of select="@r"/></r>
+     <r b="{string-join(distinct-values(for $s in e:s return 
+                      if (translate($s/@r,'$','')=$r) then e:bcrnf($s) else ()),
+                        ',')}"><xsl:value-of select="@r"/></r>
     </xsl:for-each>
     <xsl:for-each select="key('rrefTL',$r,$refs)">
      <r>&lt;<xsl:value-of select="@r"/></r>