list - Scala: type mismatch found in mapping -

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error: type mismatch; found : list[list[(char, int)]] required: list[(char, int)] @ q<- x

a2 reduceleft ((x,y)=>     for{       q<- x       b<- y     } yield (q::b::nil)   )

where, a2 : list[list[(char, int)]].

if a2 list[list[(char, int)]], x list[(char, int)], q (char, int), , b, how found list[list[(char, int)]]?

the problem yield returns list[(char, int)] loop returns list[list[(char, int)]].

therefore, reduceleft complains since expects return type list[(char, int)].


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