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docs: Pointer Arithmetic

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Allan Regush 2022-07-23 04:57:40 -06:00 committed by GitHub
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doc/langref.html.in
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@ -2671,6 +2671,36 @@ test "pointer array access" {
try expect(array[2] == 3);
ptr.* += 1;
try expect(array[2] == 4);
}
{#code_end#}
<p>
Zig supports pointer arithmetic. It's better to assign the pointer to {#syntax#}[*]T{#endsyntax#} and increment that variable. For example, directly incrementing the pointer from a slice will corrupt it.
</p>
{#code_begin|test|pointer_arthemtic#}
const expect = @import("std").testing.expect;
test "pointer arithmetic with many-item pointer" {
const array = [_]i32{ 1, 2, 3, 4 };
var ptr: [*]const i32 = &array;
try expect(ptr[0] == 1);
ptr += 1;
try expect(ptr[0] == 2);
}
test "pointer arithmetic with slices" {
var array = [_]i32{ 1, 2, 3, 4 };
var length: usize = 0;
var slice = array[length..array.len];
try expect(slice[0] == 1);
try expect(slice.len == 4);
slice.ptr += 1;
// now the slice is in an bad state since len has not been updated
try expect(slice[0] == 2);
try expect(slice.len == 4);
}
{#code_end#}
<p>