Language composition example throws error

[didrikmunther]

Running the code

miking-lang.github.io/docs/tutorials/mlang-tutorial.md

Line 132 in bb4acd0

utest eval (Add (If (False(), Num 0, Num 5), Num 2)) with Num 7 in

throws an error in the current version of Miking:

'syn' name conflict, found two definitions of 'Expr'

'sem' name conflict, found two definitions of 'eval'

To solve it, you need to inherit Expr and eval from a base language:

lang MyBase
  syn Expr =

  sem eval =
end

...

lang Arith = MyBase
...

lang MyBool = MyBase
...