IsDef.jl

For installation or usage, open julia repl and run

using IsDef

which gives you access to following functions

• isdef(f, arg1, arg2)::Bool / isdef(f, Arg1Type, Arg2Type)::Bool checks whether a function is defined for the given types.

  If at least one of the arguments is not a type, all arguments are automatically converted to types for you.

• Out(f, arg1, arg2)::ReturnType / Out(f, Arg1Type, Arg2Type)::ReturnType returns the returntype of the given functioncall.

  Note, that Out may return an abstract type that is wider than necessary, like e.g. Any. If a functioncall is not defined, or predictably throws an error, IsDef.NotApplicable is returned. Out is internally used by isdef.

Internally of Out(f, Arg1Type, Arg2Type) a one-argument-version of Out is used which expects a single Tuple type, specifying the entire call signature. This is the heart of the IsDef package. For the example it would be

• Out(Tuple{typeof(f), Arg1Type, Arg2Type})

If you want to specify inference of your method (output of Out), or whether it is defined (output of isdef), you need to overload this very one-argument method of Out. For the example it could be

• Out(::Type{<:Tuple{typeof(f), Arg1Type, Arg2Type, Vararg}}) = ReturnType

Enjoy maintainable type inference.

Manual Outline

• Manual
• • Example application: Use isdef for Traits
  • Why not using Julia's builtin type-inference directly?
  • Automatic Code Generation
  • isdef(f, ...)
  • Out(f, ...)
  • What if I only have a function-type? Use apply.
  • ValTypes

Library Index

• IsDef.Utils.ValTypes.ValType
• IsDef.Out
• IsDef.Utils.ValTypes.ValTypeof
• IsDef.apply
• IsDef.isdef
• IsDef.revise!