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@ -41,22 +41,38 @@ pub fn main() void {
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var my_result: u4 = undefined;
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var overflowed: bool = undefined;
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overflowed = @addWithOverflow(u4, a, b, &my_result);
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//
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// Check out our fancy formatting! b:0>4 means, "print
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// as a binary number, zero-pad right-aligned four digits."
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// The print() below will produce: "1101 + 0101 = 0010 (true)".
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// Let's make sense of this answer by counting up from 1101:
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print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{ a, b, my_result, overflowed });
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// Let's make sense of this answer. The value of 'b' in decimal is 5.
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// Let's add 5 to 'a' but go one by one and see where it overflows:
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//
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// Overflowed?
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// 1101 + 1 = 1110 No.
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// 1110 + 1 = 1111 No.
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// 1111 + 1 = 0000 Yes! (Real answer is 10000)
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// 0000 + 1 = 0001 No.
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// 0001 + 1 = 0010 No.
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// a | b | result | overflowed?
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// ----------------------------------
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// 1101 + 0001 = 1110 | false
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// 1110 + 0001 = 1111 | false
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// 1111 + 0001 = 0000 | true (the real answer is 10000)
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// 0000 + 0001 = 0001 | false
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// 0001 + 0001 = 0010 | false
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//
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// Also, check out our fancy formatting! b:0>4 means, "print
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// as a binary number, zero-pad right-aligned four digits."
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print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{ a, b, my_result, overflowed });
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// In the last two lines the value of 'a' is corrupted because there was
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// an overflow in line 3, but the operations of lines 4 and 5 themselves
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// do not overflow.
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// There is a difference between
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// - a value, that overflowed at some point and is now corrupted
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// - a single operation that overflows and maybe causes subsequent errors
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// In practise we usually notice the overflowed value first and have to work
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// our way backwards to the operation that caused the overflow.
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//
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// If there was no overflow at all while adding 5 to a, what value would
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// 'my_result' hold? Write the answer in into 'expected_result'.
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const expected_result: u8 = ???;
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print(". Without overflow: {b:0>8}. ", .{expected_result});
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print(". Furthermore, ", .{});
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print("Furthermore, ", .{});
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// Here's a fun one:
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//
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