-- solution 1

-- local lasttitle = nil
--
-- function xml.functions.test_b(t)
--     local title = xml.text(t, "c")
--     local content = xml.text(t, "d")
--     context.startxrow()
--     context.startxcell( { background="color", backgroundcolor="yellow" } )
--     if lasttitle == title then
--         context.color( { "red" }, title)
--     else
--         lasttitle = title
--         context.color( { "blue" }, title)
--     end
--     context.stopxcell()
--     context.startxcell()
--     context(content)
--     context.stopxcell()
--     context.stopxrow()
-- end

-- solution 2

-- local titles = { }
--
-- function xml.functions.reset_b(t)
--     titles = { }
-- end
--
-- function xml.functions.test_b(t)
--     local title = xml.text(t, "c")
--     local content = xml.text(t, "d")
--     context.startxrow()
--     context.startxcell( { background="color", backgroundcolor="yellow" } )
--     if titles[title] then
--         context.color( { "red" }, title)
--     else
--         titles[title] = true
--         context.color( { "blue" }, title)
--     end
--     context.stopxcell()
--     context.startxcell()
--     context(content)
--     context.stopxcell()
--     context.stopxrow()
-- end

-- solution 3

function xml.functions.test_b(t)
    local title = xml.text(t, "c")
    local content = xml.text(t, "d")
    context.startxrow()
    context.startxcell( { background="color", backgroundcolor="yellow" } )
    if xml.text(t,"./preceding-sibling::/[-1]") == title then
        context.color( { "red" }, title)
    else
        context.color( { "blue" }, title)
    end
    context.stopxcell()
    context.startxcell()
    context(content)
    context.stopxcell()
    context.stopxrow()
end