2 min read
Fallthrough statements
Expression switches … In a case or default clause, the last non-empty statement may be a (possibly labeled) “fallthrough” statement to indicate that control should flow from the end of this clause to the first statement of the next clause. Otherwise control flows to the end of the “switch” statement. A “fallthrough” statement may appear as the last statement of all but the last clause of an expression switch.
2 min read
Case expressions
I’m back live streaming again! Join me in just over an hour! Bring your questions, too! Expression switches … If a case expression is untyped, it is first implicitly converted to the type of the switch expression. For each (possibly converted) case expression x and the value t of the switch expression, x == t must be a valid comparison. In other words, the switch expression is treated as if it were used to declare and initialize a temporary variable t without explicit type; it is that value of t against which each case expression x is tested for equality.
2 min read
Switch expressions
Expression switches … If the switch expression evaluates to an untyped constant, it is first implicitly converted to its default type. The predeclared untyped value nil cannot be used as a switch expression. The switch expression type must be comparable. In this paragraph, “switch expression” refers to the expression that optionally comes after the switch keyword, as in: switch len(x) { So first off, if it’s a untyped constant, it’s first converted to its default type.
2 min read
Expression switches
Expression switches In an expression switch, the switch expression is evaluated and the case expressions, which need not be constants, are evaluated left-to-right and top-to-bottom; the first one that equals the switch expression triggers execution of the statements of the associated case; the other cases are skipped. If no case matches and there is a “default” case, its statements are executed. There can be at most one default case and it may appear anywhere in the “switch” statement.
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2 min read
Switch statements
Yesterday we looked at if statements, which allows conditional execution of two branches. And we saw how by chaining else if we can extend that to an arbitrary number of branches. But there’s often a cleaner way to handle multiple branches: Switch statements “Switch” statements provide multi-way execution. An expression or type is compared to the “cases” inside the “switch” to determine which branch to execute. SwitchStmt = ExprSwitchStmt | TypeSwitchStmt .
3 min read
If statements
Today I’ll be live coding again. I hope you can join, and ask your Go-related questions as I continue to hack away on my open-source project, using TDD. Catch the stream on YouTube. Have you ever tried to explain an “if” statement in as few words as possible? It’s such a simple concept, that I don’t think I’ve ever bothered trying to explain it. Well, today’s section of the Go spec does explain it.
1 min read
Assignability in Assignments
It hardly needs to be stated that in an assignment, a value must be assignable, but here we are… Assignment statements … In assignments, each value must be assignable to the type of the operand to which it is assigned… We’ve already talked about assignability, so we won’t go into those details here. But there are some special cases to discuss: … with the following special cases: Any typed value may be assigned to the blank identifier.
2 min read
Assignment order
We’ve already talked about the order of evaluation in Go. And while that’s perfectly relevant here, it’s only one piece of the puzzle when it comes to ordering with assignment operations: Assignment statements … The assignment proceeds in two phases. First, the operands of index expressions and pointer indirections (including implicit pointer indirections in selectors) on the left and the expressions on the right are all evaluated in the usual order.
2 min read
Tuple assignments
Yesterday (as well as in earlier emails) I mentioned multiple-assignments in a single statement. Today we see how they’re defined to work. As such, there’s not really an new material here, but we’ll cover it just the same. Assignment statements … A tuple assignment assigns the individual elements of a multi-valued operation to a list of variables. There are two forms. In the first, the right hand operand is a single multi-valued expression such as a function call, a channel or map operation, or a type assertion.
2 min read
I'm back!
Sorry for going silent without warning. I took a holiday, and due to a technical snafu, failed to send the announcement, so you’d know not to expect emails from me for a week and a half. Anyway, I’m back now… Let’s jump back into our tour through assignment statments, with an explanation of the special assignment/arithmetic operator combinations. You know, those things like +=, -=, and <<=: Assignment statements …
2 min read
Assignment statements
Assignment statements An assignment replaces the current value stored in a variable with a new value specified by an expression. Assignments should be familiar to you. They’re pretty fundamental to almost all programming languages. But there are a few aspects to Go’s assignments that are worth calling out. … An assignment statement may assign a single value to a single variable, or multiple values to a matching number of variables.