grammar.txt

<pklx>
    <stmt>
    <knowld>


<stmt>
    <name> = <knowld>


<knowld>
    <expr> <binop> <expr>
    <unop> <expr>


<expr>
    <name>
    ( <knowld> )
    

<binop>
    ( [[ )? letter ( letter | digit | space )* ( ]] )?


<unop>
    ( [[ )? letter ( letter | digit | space )* ( ]] )?


<name>
    ( [[ )? letter ( letter | digit | space )* ( ]] )?


letter
    a, ..., z, A, ..., Z


digit
    0, ..., 9