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% for Loops
The for loop is used to loop a particular number of times. Rust's for loops
work a bit differently than in other systems languages, however. Rust's for
loop doesn't look like this "C-style" for loop:
for (x = 0; x < 10; x++) {
printf( "%d\n", x );
}
Instead, it looks like this:
for x in 0..10 {
println!("{}", x); // x: i32
}
In slightly more abstract terms,
for var in expression {
code
}
The expression is an iterator, which we will discuss in more depth later in the
guide. The iterator gives back a series of elements. Each element is one
iteration of the loop. That value is then bound to the name var, which is
valid for the loop body. Once the body is over, the next value is fetched from
the iterator, and we loop another time. When there are no more values, the
for loop is over.
In our example, 0..10 is an expression that takes a start and an end position,
and gives an iterator over those values. The upper bound is exclusive, though,
so our loop will print 0 through 9, not 10.
Rust does not have the "C-style" for loop on purpose. Manually controlling
each element of the loop is complicated and error prone, even for experienced C
developers.
We'll talk more about for when we cover iterators, later in the Guide.