How can I disambiguate a grammar. I have this a?0.1 0.3 that returns this two parses:

{:parses
    ([:pattern
      [:cat [:degrade [:word "a"] [:op-degrade]] [:float "0.1"] [:float "0.3"]]]
     [:pattern
      [:cat
       [:degrade [:word "a"] [:op-degrade [:degrade-amount "0.1"]]]
       [:float "0.3"]]])}

pattern = cat (<ws> <'.'> <ws> cat)*

ws = #"\s+"
word = #"[a-zA-Z0-9]([a-zA-Z0-9]*)"
int = #"[0-9]+"
float = #"(?<!\?)\d+(\.\d+)"
<token> = word | int | float | degrade

cat = token (<ws>? token)*
degrade-amount = #"([0-9]*[.])?[0-9]+"
op-degrade = <'?'> degrade-amount?
degrade = token op-degrade