set_option eqn_compiler.lemmas false -- TODO(Leo): remove
definition f : string → nat → nat
| "hello world" 1 := 0
| "hello world" _ := 1
| "bye"         1 := 2
| _             _ := 3

#eval f "hello world" 1
#eval f "hello world" 2
#eval f "bye" 1
#eval f "bye" 2
#eval f "hello" 1