1 files changed, 75 insertions, 0 deletions
diff --git a/tex/context/base/chem-ini.lua b/tex/context/base/chem-ini.lua
new file mode 100644
index 000000000..908749092
--- /dev/null
+++ b/tex/context/base/chem-ini.lua
@@ -0,0 +1,75 @@
+if not modules then modules = { } end modules ['chem-ini'] = {
+    version   = 1.001,
+    comment   = "companion to chem-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local format, texsprint = string.format, tex.sprint
+local lpegmatch = lpeg.match
+
+local trace_molecules = false  trackers.register("chemistry.molecules",  function(v) trace_molecules = v end)
+
+local ctxcatcodes = tex.ctxcatcodes
+
+chemicals = chemicals or { }
+
+--[[
+<p>The next code is an adaptation of code from Wolfgang Schuster
+as posted on the mailing list. This version supports nested
+braces and unbraced integers as scripts. We could consider
+spaces as terminals for them but first let collect a bunch
+of input then.</p>
+]]--
+
+-- some lpeg, maybe i'll make an syst-lpg module
+
+local lowercase   = lpeg.R("az")
+local uppercase   = lpeg.R("AZ")
+local backslash   = lpeg.P("\\")
+local csname      = backslash * lpeg.P(1) * (1-backslash)^0
+local plus        = lpeg.P("+") / "\\textplus "
+local minus       = lpeg.P("-") / "\\textminus "
+local digit       = lpeg.R("09")
+local sign        = plus + minus
+local cardinal    = digit^1
+local integer     = sign^0 * cardinal
+
+local leftbrace   = lpeg.P("{")
+local rightbrace  = lpeg.P("}")
+local nobrace     = 1 - (leftbrace + rightbrace)
+local nested      = lpeg.P { leftbrace * (csname + sign + nobrace + lpeg.V(1))^0 * rightbrace }
+local any         = lpeg.P(1)
+
+local subscript   = lpeg.P("_")
+local superscript = lpeg.P("^")
+local somescript  = subscript + superscript
+
+--~ local content     = lpeg.Cs(nested + integer + sign + any)
+local content     = lpeg.Cs(csname + nested + sign + any)
+
+-- could be made more efficient
+
+local lowhigh    = lpeg.Cc("\\lohi{%s}{%s}") * subscript   * content * superscript * content / format
+local highlow    = lpeg.Cc("\\hilo{%s}{%s}") * superscript * content * subscript   * content / format
+local low        = lpeg.Cc("\\low{%s}")      * subscript   * content                         / format
+local high       = lpeg.Cc("\\high{%s}")     * superscript * content                         / format
+local justtext   = (1 - somescript)^1
+local parser     = lpeg.Cs((csname + lowhigh + highlow + low + high + sign + any)^0)
+
+chemicals.moleculeparser = parser -- can be used to avoid functioncall
+
+function chemicals.molecule(str)
+    return lpegmatch(parser,str)
+end
+
+function commands.molecule(str)
+    if trace_molecules then
+        local rep = lpegmatch(parser,str)
+        logs.report("chemistry", "molecule %s => %s",str,rep)
+        texsprint(ctxcatcodes,rep)
+    else
+        texsprint(ctxcatcodes,lpegmatch(parser,str))
+    end
+end