write floats in scientific notation

Author: mjreno

flopy4/mf6/codec/reader/grammar/basic.lark

@@ -4,7 +4,7 @@ block_name: CNAME [INT]
 _list: line*
 line: [WS] item+ _NL+
 item: word | NUMBER
-word: /[a-zA-Z0-9._'~,-\\(\\)]+/
+word: /[a-zA-Z0-9._+'~,-\\(\\)]+/
 
 %import common.NEWLINE -> _NL
 %import common.WS

flopy4/mf6/codec/writer/filters.py

@@ -115,7 +115,7 @@ def array2string(value: NDArray) -> str:
     format = (
         "%d"
         if np.issubdtype(value.dtype, np.integer)
-        else "%.9f"
+        else "%.9e"
         if np.issubdtype(value.dtype, np.floating)
         else "%s"
     )