(re-)Implement GMX RTP parser using lark-parser

setup.cfg

@@ -34,6 +34,7 @@ install-requires =  # ?? requires-dist?
     pbr
     numpy
     networkx ~= 2.0
+    lark
 zip-safe = False
 
 [options.extras_require]

vermouth/__init__.py

@@ -32,16 +32,17 @@
 
 
 # Find the data directory once.
+from pathlib import Path
 try:
     import pkg_resources
 except ImportError:
     import os
-    DATA_PATH = os.path.join(os.path.dirname(__file__), 'data')
+    DATA_PATH = Path(os.path.dirname(__file__)) / 'data'
     del os
 else:
-    DATA_PATH = pkg_resources.resource_filename('vermouth', 'data')
+    DATA_PATH = Path(pkg_resources.resource_filename('vermouth', 'data'))
     del pkg_resources
-
+del Path
 del pbr
 
 try:

vermouth/data/grammars/gmx_rtp.lark

@@ -0,0 +1,37 @@
+_header{name}: "[" name "]" _NL+
+
+start: _NL* bondedtypes? residue+
+bondedtypes: _header{"bondedtypes"} INT~8 _NL*
+
+residue: _header{NAME} mol_section*
+
+?mol_section: atomsection
+            | _header{"bonds"} bond+         -> bonds
+            | _header{"angles"} angle+       -> angles
+            | _header{"dihedrals"} dihedral+ -> dihedrals
+            | _header{"impropers"} dihedral+ -> impropers
+            | _header{"cmap"} cmap+          -> cmaps
+            | _header{"exclusions"} bond+    -> exclusions
+
+name_line: NAME INT _NL*
+
+atomsection: _header{"atoms"} atom+
+atom: NAME NAME SIGNED_NUMBER INT _NL*
+
+INTERACTION_ATOM: ("+"+|"-"+)? NAME
+bond: INTERACTION_ATOM~2 [parameters] _NL+
+angle: INTERACTION_ATOM~3 [parameters] _NL+
+dihedral: INTERACTION_ATOM~4 [parameters] _NL+
+cmap: INTERACTION_ATOM~5 [parameters] _NL+
+
+parameters: (NAME|SIGNED_NUMBER+)
+
+NAME: /\w/+
+VALUE: /./+
+COMMENT: /;[^\n]*/
+%ignore COMMENT
+
+%import common (INT, SIGNED_NUMBER)
+%import common.NEWLINE -> _NL
+%import common.WS_INLINE
+%ignore WS_INLINE