BNF for Math Lang

#Words
<Inner_Block> ::= <Block_Start><Block><Block_End>
<Block>*      ::= <Expression>(<Exp_Sep><Expression>)*
<Expression>  ::= <Sum>|<Assignment>
<Assignment>  ::= <Name><Assign_Op><Inner_Block>
<Sum>         ::= <Difference>(<Add_Op><Difference>)*
<Difference>  ::= <Product>(<Sub_Op><Product>)*
<Product>     ::= <Quotient>(<Mul_Op><Quotient>)*
<Quotient>    ::= <Term>(<Div_Op><Term>)*
<Term>        ::= <Number>|<Call>|<Inner_Block>
<Call>        ::= <Call_Op><Name><Inner_Block>
<Number>      ::= {<Sign>}<Digit><Digit_0>*
<Name>        ::= <Letter>(<Letter><Digit_0><U_Score>)*
<Sign>        ::= <Add_Op>|<Sub_Op>
# Consts
<Letter>      ::= [a-zA-Z]
<Digit>       ::= [1-9]
<Digit_0>     ::= [0-9]
<Exp_Sep>     ::= ";"
<Block_Start> ::= "("
<Block_End>   ::= ")"
<Add_Op>      ::= "+"
<Sub_Op>      ::= "-"
<Mul_Op>      ::= "*"
<Div_Op>      ::= "/"
<Call_Op>     ::= "$"
<U_Score>     ::= "_"