Fixing grammar

Fixing the grammar:

• Operation order:
  • Expression like Trans1 @ Trans2 * Trans3 @ Trans4 is the same as (Trans1 @ Trans2) * (Trans3 @ Trans4), i.e. the product (or other operation) of matrices products
• Distinguish between operations on variables and transformations:
  • var1*var2 -> product_v -> product
  • Trans1/var2 -> division_t -> Division