55 lines
1.8 KiB
Zig
55 lines
1.8 KiB
Zig
//
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// One of the more common uses of 'comptime' function parameters is
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// passing a type to a function:
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//
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// fn foo(comptime MyType: type) void { ... }
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//
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// In fact, types are ONLY available at compile time, so the
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// 'comptime' keyword is required here.
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//
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// Please take a moment put on the wizard hat which has been
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// provided for you. We're about to use this ability to implement
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// a generic function.
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//
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const print = @import("std").debug.print;
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pub fn main() void {
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// Here we declare arrays of three different types and sizes
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// at compile time from a function call. Neat!
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const s1 = makeSequence(u8, 3); // creates a [3]u8
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const s2 = makeSequence(u32, 5); // creates a [5]u32
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const s3 = makeSequence(i64, 7); // creates a [7]i64
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print("s1={any}, s2={any}, s3={any}\n", .{ s1, s2, s3 });
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}
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// This function is pretty wild because it executes at runtime
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// and is part of the final compiled program. The function is
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// compiled with unchanging data sizes and types.
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//
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// And yet it ALSO allows for different sizes and types. This
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// seems paradoxical. How could both things be true?
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//
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// To accomplish this, the Zig compiler actually generates a
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// separate copy of the function for every size/type combination!
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// So in this case, three different functions will be generated
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// for you, each with machine code that handles that specific
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// data size and type.
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//
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// Please fix this function so that the 'size' parameter:
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//
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// 1) Is guaranteed to be known at compile time.
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// 2) Sets the size of the array of type T (which is the
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// sequence we're creating and returning).
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//
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fn makeSequence(comptime T: type, comptime size: usize) [size]T {
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var sequence: [size]T = undefined;
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var i: usize = 0;
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while (i < size) : (i += 1) {
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sequence[i] = @intCast(T, i) + 1;
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}
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return sequence;
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}
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