42 lines
1.3 KiB
Zig
42 lines
1.3 KiB
Zig
//
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// The tricky part is that the pointer's mutability (var vs const) refers
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// to the ability to change what the pointer POINTS TO, not the ability
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// to change the VALUE at that location!
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//
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// const locked: u8 = 5;
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// var unlocked: u8 = 10;
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//
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// const p1: *const u8 = &locked;
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// var p2: *const u8 = &locked;
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//
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// Both p1 and p2 point to constant values which cannot change. However,
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// p2 can be changed to point to something else and p1 cannot!
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//
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// const p3: *u8 = &unlocked;
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// var p4: *u8 = &unlocked;
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// const p5: *const u8 = &unlocked;
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// var p6: *const u8 = &unlocked;
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//
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// Here p3 and p4 can both be used to change the value they point to but
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// p3 cannot point at anything else.
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// What's interesting is that p5 and p6 act like p1 and p2, but point to
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// the value at "unlocked". This is what we mean when we say that we can
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// make a constant reference to any value!
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//
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const std = @import("std");
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pub fn main() void {
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var foo: u8 = 5;
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var bar: u8 = 10;
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// Please define pointer "p" so that it can point to EITHER foo or
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// bar AND change the value it points to!
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var p: *u8 = undefined;
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p = &foo;
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p.* += 1;
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p = &bar;
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p.* += 1;
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std.debug.print("foo={}, bar={}\n", .{ foo, bar });
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}
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