--- a/src/SbpOperators/readoperator.jl	Wed Jan 12 14:59:03 2022 +0100
+++ b/src/SbpOperators/readoperator.jl	Wed Jan 12 15:32:58 2022 +0100
@@ -4,7 +4,8 @@
 export get_stencil_set
 
 export parse_stencil
-export parse_rational
+export parse_scalar
+export parse_tuple
 
 export sbp_operators_path
 
@@ -32,6 +33,7 @@
     # Parsing as rationals is intentional, allows preserving exactness, which can be lowered using converts or promotions later.
 # TODO: readoperator.jl file name?
 # TODO: Remove references to toml for dict-input arguments
+# TODO: Documetning the format: Allows representing rationals as strings
 
 """
     read_stencil_set(fn; filters)
@@ -109,6 +111,22 @@
     end
 end
 
+
+function parse_scalar(toml)
+    try
+        return parse_rational(toml)
+    catch e
+        throw(ArgumentError("must be a number or a string representing a number."))
+    end
+end
+
+function parse_tuple(toml)
+    if !(toml isa Array)
+        throw(ArgumentError("argument must be an array"))
+    end
+    return Tuple(parse_scalar.(toml))
+end
+
 function parse_rational(toml)
     if toml isa String
         expr = Meta.parse(replace(toml, "/"=>"//"))