1 min read
Type definitions
Some of the minutiae we’ve gone over about underlying types, and type identity are finally starting to come together… Type definitions A type definition creates a new, distinct type with the same underlying type and operations as the given type and binds an identifier, the type name, to it. TypeDef = identifier [ TypeParameters ] Type . The new type is called a defined type. It is different from any other type, including the type it is created from.
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Writing Go and doin' DevOps on Backend Banter
Listen as I discuss Go, DevOps, and more, with Lane Wagner on the Backend Banter podcast.
2 min read
Alias declarations
Alias declarations An alias declaration binds an identifier to the given type. AliasDecl = identifier "=" Type . Within the scope of the identifier, it serves as an alias for the type. type ( nodeList = []*Node // nodeList and []*Node are identical types Polar = polar // Polar and polar denote identical types ) Aliases are a feature you likely won’t use frequently. You may never use it, in fact.
1 min read
Type declarations
We’ve already talked about the different types availabe in Go, but now we’ll see how to declare them… just in case it wasn’t already obvious. Type declarations A type declaration binds an identifier, the type name, to a type. Type declarations come in two forms: alias declarations and type definitions. TypeDecl = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) . TypeSpec = AliasDecl | TypeDef . We’ll talk about these two different forms in the coming days.
2 min read
Iota, continued
No live stream today. My office/recording studio is being painted. I’ll be back next week with more linter building! One last detail on iota… Iota … By definition, multiple uses of iota in the same ConstSpec all have the same value: const ( bit0, mask0 = 1 << iota, 1<<iota - 1 // bit0 == 1, mask0 == 0 (iota == 0) bit1, mask1 // bit1 == 2, mask1 == 1 (iota == 1) _, _ // (iota == 2, unused) bit3, mask3 // bit3 == 8, mask3 == 7 (iota == 3) ) This last example exploits the [implicit repetition](https://go.
2 min read
Iota
You may recall from yesterday that you can omit the constant expression for all but the first ConstantSpec in a parenthesized constant declaration, but that it wasn’t very useful by itself. Enter iota… Iota Within a constant declaration, the predeclared identifier iota represents successive untyped integer constants. Its value is the index of the respective ConstSpec in that constant declaration, starting at zero. It can be used to construct a set of related constants:
2 min read
Omitting constant expressions
Constant declarations … Within a parenthesized const declaration list the expression list may be omitted from any but the first ConstSpec. Such an empty list is equivalent to the textual substitution of the first preceding non-empty expression list and its type if any. Omitting the list of expressions is therefore equivalent to repeating the previous list. The number of identifiers must be equal to the number of expressions in the previous list.
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1 min read
Are you maintaining dead code?
I’m taking a break from the Go spec today to talk about a new tool I just discovered, that saved me a bunch of work. One of the clients I’m working with has a rather old codebase, filled with a bunch of retired features. It was a laborious task to go through all the thousands of files in the project to see which functions and types were no longer being used.
2 min read
Constant types
Long-time readers may recall that constants may be typed or untyped. Today we expore the details of how such constants are declared. Constant declarations … If the type is present, all constants take the type specified, and the expressions must be assignable to that type, which must not be a type parameter. If the type is omitted, the constants take the individual types of the corresponding expressions. If the expression values are untyped constants, the declared constants remain untyped and the constant identifiers denote the constant values.
2 min read
Constant declarations
I’m live streaming again! You’ll probably read this after the fact, but if not, come join me live, or catch the replay! I’ll be building a real-world linter from scratch, picking up from the tutorial I did 2 weeks ago. If you’ve been reading me for a while, you’ll recall we’ve already talked about constants in Go. However, we’ve done it in a slightly more abstract sense; constant literals, and they’re types.
1 min read
Uniqueness of identifiers
Uniqueness of identifiers Given a set of identifiers, an identifier is called unique if it is different from every other in the set. Two identifiers are different if they are spelled differently, or if they appear in different packages and are not exported. Otherwise, they are the same. This is pretty simple stuff, but it’s obviously worth being explicit. foo and bar are obviously different identifiers. Further, a in package foo, and a in package bar are different identifiers, because although they are spelled the same, they are not exported, and are in different packages.