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Diffstat (limited to 'exercises/50_no_value.zig')
| -rw-r--r-- | exercises/50_no_value.zig | 84 |
1 files changed, 0 insertions, 84 deletions
diff --git a/exercises/50_no_value.zig b/exercises/50_no_value.zig deleted file mode 100644 index 8708d2d..0000000 --- a/exercises/50_no_value.zig +++ /dev/null @@ -1,84 +0,0 @@ -// -// "We live on a placid island of ignorance in the midst -// of black seas of infinity, and it was not meant that -// we should voyage far." -// -// from The Call of Cthulhu -// by H. P. Lovecraft -// -// Zig has at least four ways of expressing "no value": -// -// * undefined -// -// var foo: u8 = undefined; -// -// "undefined" should not be thought of as a value, but as a way -// of telling the compiler that you are not assigning a value -// _yet_. Any type may be set to undefined, but attempting -// to read or use that value is _always_ a mistake. -// -// * null -// -// var foo: ?u8 = null; -// -// The "null" primitive value _is_ a value that means "no value". -// This is typically used with optional types as with the ?u8 -// shown above. When foo equals null, that's not a value of type -// u8. It means there is _no value_ of type u8 in foo at all! -// -// * error -// -// var foo: MyError!u8 = BadError; -// -// Errors are _very_ similar to nulls. They _are_ a value, but -// they usually indicate that the "real value" you were looking -// for does not exist. Instead, you have an error. The example -// error union type of MyError!u8 means that foo either holds -// a u8 value OR an error. There is _no value_ of type u8 in foo -// when it's set to an error! -// -// * void -// -// var foo: void = {}; -// -// "void" is a _type_, not a value. It is the most popular of the -// Zero Bit Types (those types which take up absolutely no space -// and have only a semantic value. When compiled to executable -// code, zero bit types generate no code at all. The above example -// shows a variable foo of type void which is assigned the value -// of an empty expression. It's much more common to see void as -// the return type of a function that returns nothing. -// -// Zig has all of these ways of expressing different types of "no value" -// because they each serve a purpose. Briefly: -// -// * undefined - there is no value YET, this cannot be read YET -// * null - there is an explicit value of "no value" -// * errors - there is no value because something went wrong -// * void - there will NEVER be a value stored here -// -// Please use the correct "no value" for each ??? to make this program -// print out a cursed quote from the Necronomicon. ...If you dare. -// -const std = @import("std"); - -const Err = error{Cthulhu}; - -pub fn main() void { - var first_line1: *const [16]u8 = ???; - first_line1 = "That is not dead"; - - var first_line2: Err!*const [21]u8 = ???; - first_line2 = "which can eternal lie"; - - std.debug.print("{s} {s} / ", .{ first_line1, first_line2 }); - - printSecondLine(); -} - -fn printSecondLine() ??? { - var second_line2: ?*const [18]u8 = ???; - second_line2 = "even death may die"; - - std.debug.print("And with strange aeons {s}.\n", .{second_line2.?}); -} |