Block and Statements
A block is an expression contains sequence of statements and an optional expression.
{
statement1
statement2
expression
}
For example, the code above will execute statement1, statement2
and evaluate expression in order. The evaluation result of the block is the
evaluation result of the expression. If the last one expression is omitted,
the block will result in (), which type is Unit.
A statement can be a variable declaration, variable assignment, or any
expression which type is Unit.
A block is also associated with a namespace scope. In the main clause, the variable a declared in the inner block will shadow the outer a. It is only visible within the inner block.
fn main {
let a = 100
{
let mut a = 0
println("checkpoint 1")
a = a + 1
}
println("checkpoint 2")
println(f())
}
fn f() -> Int {
let b = 3.14
let result = {
let b = 1
println("checkpoint 3")
b + 5
}
result // same as `return result` here
}