1 min read
Built-in functions
We’ve just finished up the rather long section on different types of statements. There’s only a few more sections in the spec, before we finish this series. And today we start looking at Built-in functions! Built-in functions Built-in functions are predeclared. They are called like any other function but some of them accept a type instead of an expression as the first argument. The built-in functions do not have standard Go types, so they can only appear in call expressions; they cannot be used as function values.
2 min read
Modifying return values in deferred functions
Oops! It seems that Friday’s email got stuck, and didn’t actually send until late Monday. Meaning you probably got two emails in the same day, and out of order. I hope it didn’t bother anyone too much. I should probably make a joke about how it was deferred… Nah! Today we’ll be finishing up the section on the defer keyword, with one special capability that it affords us. Defer statements …
3 min read
Defer execution order
Let’s talk about some of the nuance surrounding defer that’s often lost, or simply forgotten. Defer statements … Each time a “defer” statement executes, the function value and parameters to the call are evaluated as usual and saved anew but the actual function is not invoked. Instead, deferred functions are invoked immediately before the surrounding function returns, in the reverse order they were deferred. That is, if the surrounding function returns through an explicit return statement, deferred functions are executed after any result parameters are set by that return statement but before the function returns to its caller.
2 min read
Defer statements
We’re at the last item in the “Statements” section of the spec, before we move on to built-in functions. And naturally, the last one is… the defer statement~ Defer statements A “defer” statement invokes a function whose execution is deferred to the moment the surrounding function returns, either because the surrounding function executed a return statement, reached the end of its function body, or because the corresponding goroutine is panicking.
1 min read
Fallthrough statements
Fallthrough statements A “fallthrough” statement transfers control to the first statement of the next case clause in an expression “switch” statement. It may be used only as the final non-empty statement in such a clause. FallthroughStmt = "fallthrough" . Well that’s pretty straight forward. for x := range 10 { switch { case x%2 == 0: fmt.Print("X") fallthrough case x%3 == 0: fmt.Print("x") fallthrough case x%5 == 0: fmt.Print("O") } fmt.
2 min read
Goto statements
We’ve finished the discussion of the new range-over-func feature, so let’s continue where we left off before the Go 1.23 release, with a feature you’ll rarely, if ever, use. Goto statements A “goto” statement transfers control to the statement with the corresponding label within the same function. GotoStmt = "goto" Label . goto Error Unless your only programming experience has been in the BASIC language, you’ve probably learned to eschew “goto”.
3 min read
Tree walking with range-over-fun
We’ve been looking at Go 1.23’s new range-over-func feature. And we’re just about through what the spec has to say about it. Except for one thing. The example code! // iteration support for a recursive tree data structure type Tree[K cmp.Ordered, V any] struct { left, right *Tree[K, V] key K value V } func (t *Tree[K, V]) walk(yield func(key K, val V) bool) bool { return t == nil || t.
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4 min read
yield
For statements with range clause … For a function f, the iteration proceeds by calling f with a new, synthesized yield function as its argument. Let’s talk about yield today. If I’m honest, this was probably the scariest part of these new function iterators, before I started actually using them. It looks an awful lot like a new keyword, with weird usage. I know I’m not alone in thinking this.
3 min read
Iterating over functions
As mentioned yesterday, today we’re taking a bit of a step back to an earlier portion of the spec, which was just updated. Here’s the first part of the updated section of the spec (new additions emphasized): For statements with range clause A “for” statement with a “range” clause iterates through all entries of an array, slice, string or map, values received on a channel, integer values from zero to an upper limit [Go 1.
2 min read
Go 1.23.0 has been released!
I missed the last couple of days. Oops! It’s a busy time here, as I’m preparing for an international move, and balancing a new business venture I’m working on. But I’m back today! The big news in the Go world is that on Tuesday, Go 1.23.0 was released! What this means for us, as we venture through the Go spec, is that there are new changes to the spec we need to talk about!
1 min read
Continue statements
Let’s continue… haha See what I did there? Bleh, okay. Continue statements A “continue” statement begins the next iteration of the innermost enclosing “for” loop by advancing control to the end of the loop block. The “for” loop must be within the same function. ContinueStmt = "continue" [ Label ] . There’s not a lot necessary to say here. continue works very much like break. The scoping rules are essentially the same.