is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons.CHAPTER 12. TYPES 149 julia> addy(y) = x

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons. CHAPTER 12. TYPES 149 julia> addy(y) =

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons. julia> addy(y) = x -> x + y addy (generic

is written: julia> struct MyUndefVarError <: Exception var::Symbol end julia> Base.showerror(io::IO, e::MyUndefVarError) = print(io, e.var, " not defined") Note When writing an error message, it new variable bindings each time they run. The variable need not be immediately assigned: julia> var1 = let x for i in 1:5 (i == 4) && (x = i; break) end x end 4 Whereas assignments might reassign distinct, but not guaranteed to be printed the same way across sessions. julia> typeof(x -> x + 1) var"#9#10" Types of closures are not necessarily singletons. julia> addy(y) = x -> x + y addy (generic