impure_func_t3.m:019: In call to predicate `io.print'/3:
impure_func_t3.m:019:   warning: unnecessary `impure' indicator.
impure_func_t3.m:019:   No purity indicator is necessary.
impure_func_t3.m:019: In call to impure function
impure_func_t3.m:019:   `impure_func_t3.get_counter'/0:
impure_func_t3.m:019:   purity error: call must be in an explicit unification
impure_func_t3.m:019:   which is preceded by `impure' indicator.