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125 | //
// You can even create anonymous struct literals without field
// names:
//
// .{
// false,
// @as(u32, 15),
// @as(f64, 67.12)
// }
//
// We call these "tuples", which is a term used by many
// programming languages for a data type with fields referenced
// by index order rather than name. To make this possible, the Zig
// compiler automatically assigns numeric field names 0, 1, 2,
// etc. to the struct.
//
// Since bare numbers are not legal identifiers (foo.0 is a
// syntax error), we have to quote them with the @"" syntax.
// Example:
//
// const foo = .{ true, false };
//
// print("{} {}\n", .{foo.@"0", foo.@"1"});
//
// The example above prints "true false".
//
// Hey, WAIT A SECOND...
//
// If a .{} thing is what the print function wants, do we need to
// break our "tuple" apart and put it in another one? No! It's
// redundant! This will print the same thing:
//
// print("{} {}\n", foo);
//
// Aha! So now we know that print() takes a "tuple". Things are
// really starting to come together now.
//
const print = @import("std").debug.print;
pub fn main() void {
// A "tuple":
const foo = .{
true,
false,
@as(i32, 42),
@as(f32, 3.141592),
};
// We'll be implementing this:
printTuple(foo);
// This is just for fun, because we can:
const nothing = .{};
print("\n", nothing);
}
// Let's make our own generic "tuple" printer. This should take a
// "tuple" and print out each field in the following format:
//
// "name"(type):value
//
// Example:
//
// "0"(bool):true
//
// You'll be putting this together. But don't worry, everything
// you need is documented in the comments.
fn printTuple(tuple: anytype) void {
// 1. Get a list of fields in the input 'tuple'
// parameter. You'll need:
//
// @TypeOf() - takes a value, returns its type.
//
// @typeInfo() - takes a type, returns a TypeInfo union
// with fields specific to that type.
//
// The list of a struct type's fields can be found in
// TypeInfo's Struct.fields.
//
// Example:
//
// @typeInfo(Circle).Struct.fields
//
// This will be an array of StructFields.
const fields = ???;
// 2. Loop through each field. This must be done at compile
// time.
//
// Hint: remember 'inline' loops?
//
for (fields) |field| {
// 3. Print the field's name, type, and value.
//
// Each 'field' in this loop is one of these:
//
// pub const StructField = struct {
// name: []const u8,
// type: type,
// default_value: anytype,
// is_comptime: bool,
// alignment: comptime_int,
// };
//
// You'll need this builtin:
//
// @field(lhs: anytype, comptime field_name: []const u8)
//
// The first parameter is the value to be accessed,
// the second parameter is a string with the name of
// the field you wish to access. The value of the
// field is returned.
//
// Example:
//
// @field(foo, "x"); // returns the value at foo.x
//
// The first field should print as: "0"(bool):true
print("\"{s}\"({any}):{any} ", .{
field.???,
field.???,
???,
});
}
}
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