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to be able to use it as Float or Double
Use BaseEntry<Float> instead of FloatEntry
The problem is invariant generics. BarDataSet is DataSet<BarEntryFloat>, so entries expects MutableList<BarEntryFloat>. Even though BarEntryDouble : BarEntryFloat, MutableList<BarEntryDouble> is not a MutableList<BarEntryFloat> because MutableList is invariant (it's both a producer and consumer). MutableList<T> is invariant in T because it both reads (get() → T) and writes (add(T)). Even though BarEntryDouble : BarEntryFloat, the compiler must reject the assignment to prevent this kind of unsound write: val list: MutableList<BarEntryFloat> = values // if allowed... list.add(BarEntryFloat(1f, 2f)) // would corrupt the original BarEntryDouble list! The @Suppress("UNCHECKED_CAST") cast is safe here because: * JVM erases generics at runtime — both are just MutableList on the heap * BarDataSet only reads entries from the list as BarEntryFloat, and BarEntryDouble IS a BarEntryFloat * Nothing writes a plain BarEntryFloat back into the list through BarDataSet
The problem is invariant generics. LineDataSet is LineDataSet<EntryFloat>, so entries expects MutableList<EntryFloat>. Even though EntryDouble : EntryFloat, MutableList<EntryDouble> is not a MutableList<EntryFloat> because MutableList is invariant (it's both a producer and consumer). MutableList<T> is invariant in T because it both reads (get() → T) and writes (add(T)). Even though EntryDouble : EntryFloat, the compiler must reject the assignment to prevent this kind of unsound write: val list: MutableList<EntryFloat> = values // if allowed... list.add(EntryFloat(1f, 2f)) // would corrupt the original EntryDouble list! The @Suppress("UNCHECKED_CAST") cast is safe here because: * JVM erases generics at runtime — both are just MutableList on the heap * LineDataSet only reads entries from the list as EntryFloat, and EntryDouble IS a EntryFloat * Nothing writes a plain EntryFloat back into the list through DataSet
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Before with
Floatnow with optional
Double