1 files changed, 67 insertions, 0 deletions
diff --git a/src/examples/chemicalFormulas.py b/src/examples/chemicalFormulas.py
new file mode 100644
index 0000000..63eff13
--- /dev/null
+++ b/src/examples/chemicalFormulas.py
@@ -0,0 +1,67 @@
+# chemicalFormulas.py
+#
+# Copyright (c) 2003, Paul McGuire
+#
+
+from pyparsing import Word, Optional, OneOrMore, Group, ParseException, Regex
+from pyparsing import alphas
+
+atomicWeight = {
+    "O"  : 15.9994,
+    "H"  : 1.00794,
+    "Na" : 22.9897,
+    "Cl" : 35.4527,
+    "C"  : 12.0107
+    }
+    
+def test( bnf, strg, fn=None ):
+    try:
+        print strg,"->", bnf.parseString( strg ),
+    except ParseException, pe:
+        print pe
+    else:
+        if fn != None:
+            print fn( bnf.parseString( strg ) )
+        else:
+            print
+
+digits = "0123456789"
+
+# Version 1
+element = Regex("A[cglmrstu]|B[aehikr]?|C[adeflmorsu]?|D[bsy]|"
+                "E[rsu]|F[emr]?|G[ade]|H[efgos]?|I[nr]?|Kr?|L[airu]|"
+                "M[dgnot]|N[abdeiop]?|Os?|P[abdmortu]?|R[abefghnu]|"
+                "S[bcegimnr]?|T[abcehilm]|U(u[bhopqst])?|V|W|Xe|Yb?|Z[nr]")
+
+element = Word( alphas.upper(), alphas.lower(), max=2)
+elementRef = Group( element + Optional( Word( digits ), default="1" ) )
+formula = OneOrMore( elementRef )
+
+fn = lambda elemList : sum( [ atomicWeight[elem]*int(qty) for elem,qty in elemList ] )
+test( formula, "H2O", fn )
+test( formula, "C6H5OH", fn )
+test( formula, "NaCl", fn )
+print
+
+# Version 2 - access parsed items by field name
+elementRef = Group( element("symbol") + Optional( Word( digits ), default="1" )("qty") )
+formula = OneOrMore( elementRef )
+
+fn = lambda elemList : sum( [ atomicWeight[elem.symbol]*int(elem.qty) for elem in elemList ] )
+test( formula, "H2O", fn )
+test( formula, "C6H5OH", fn )
+test( formula, "NaCl", fn )
+print
+
+# Version 3 - convert integers during parsing process
+integer = Word( digits ).setParseAction(lambda t:int(t[0]))
+elementRef = Group( element("symbol") + Optional( integer, default=1 )("qty") )
+formula = OneOrMore( elementRef )
+
+fn = lambda elemList : sum( [ atomicWeight[elem.symbol]*elem.qty for elem in elemList ] )
+test( formula, "H2O", fn )
+test( formula, "C6H5OH", fn )
+test( formula, "NaCl", fn )
+    
+
+