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https://github.com/ratfactor/ziglings
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6ad9774189
When I hit 999 exercises, I will finally have reached the ultimate state of soteriological release and no more exercises will be needed. The cycle will be complete. All that will be left is perfect quietude, freedom, and highest happiness.
85 lines
2.9 KiB
Zig
85 lines
2.9 KiB
Zig
//
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// "We live on a placid island of ignorance in the midst
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// of black seas of infinity, and it was not meant that
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// we should voyage far."
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//
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// from The Call of Cthulhu
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// by H. P. Lovecraft
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//
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// Zig has at least four ways of expressing "no value":
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//
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// * undefined
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//
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// var foo: u8 = undefined;
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//
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// "undefined" should not be thought of as a value, but as a way
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// of telling the compiler that you are not assigning a value
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// _yet_. Any type may be set to undefined, but attempting
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// to read or use that value is _always_ a mistake.
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//
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// * null
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//
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// var foo: ?u8 = null;
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//
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// The "null" primitive value _is_ a value that means "no value".
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// This is typically used with optional types as with the ?u8
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// shown above. When foo equals null, that's not a value of type
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// u8. It means there is _no value_ of type u8 in foo at all!
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//
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// * error
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//
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// var foo: MyError!u8 = BadError;
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//
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// Errors are _very_ similar to nulls. They _are_ a value, but
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// they usually indicate that the "real value" you were looking
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// for does not exist. Instead, you have an error. The example
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// error union type of MyError!u8 means that foo either holds
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// a u8 value OR an error. There is _no value_ of type u8 in foo
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// when it's set to an error!
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//
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// * void
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//
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// var foo: void = {};
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//
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// "void" is a _type_, not a value. It is the most popular of the
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// Zero Bit Types (those types which take up absolutely no space
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// and have only a semantic value. When compiled to executable
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// code, zero bit types generate no code at all. The above example
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// shows a variable foo of type void which is assigned the value
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// of an empty expression. It's much more common to see void as
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// the return type of a function that returns nothing.
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//
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// Zig has all of these ways of expressing different types of "no value"
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// because they each serve a purpose. Briefly:
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//
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// * undefined - there is no value YET, this cannot be read YET
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// * null - there is an explicit value of "no value"
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// * errors - there is no value because something went wrong
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// * void - there will NEVER be a value stored here
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//
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// Please use the correct "no value" for each ??? to make this program
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// print out a cursed quote from the Necronomicon. ...If you dare.
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//
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const std = @import("std");
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const Err = error{Cthulhu};
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pub fn main() void {
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var first_line1: *const [16]u8 = ???;
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first_line1 = "That is not dead";
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var first_line2: Err!*const [21]u8 = ???;
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first_line2 = "which can eternal lie";
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std.debug.print("{s} {s} / ", .{ first_line1, first_line2 });
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printSecondLine();
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}
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fn printSecondLine() ??? {
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var second_line2: ?*const [18]u8 = ???;
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second_line2 = "even death may die";
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std.debug.print("And with strange aeons {s}.\n", .{second_line2.?});
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}
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