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Version: ZIO 2.x

Frequently Answered Questions (FAQ)

In this page we are going to answer general questions related to the ZIO project.

In ZIO ecosystem, there are lots of data types which they have Z prefix in their names. What this prefix stands for? Does it mean, that data type is effectual?​

No, it doesn't denote that the data type is effectual. Instead, the Z prefix is used for two purposes:

  1. Polymorphic Version of Another Data Type — The Z prefix indicates a more polymorphic version of another data type, not a data type that is effectual. So for example IO and ZIO are equally effectual but ZIO is more polymorphic because it has the additional type parameter R.

  2. Term Disambiguation — There are some cases where the Z prefix is used to disambiguate a term that might otherwise be too common and create risk of name conflicts (e.g. ZPool).

This convention is true across all ZIO ecosystem. For example, in ZIO Prelude, the ZValidation is a more general version of Validation that is polymorphic in the log type. ZSet is a more polymorphic version of a Set that is polymorphic in the measure type. ZPure is more polymorphic than its type aliases in several ways as represented by its different type parameters and also serves to disambiguate it as Pure which is too general.