diff --git a/build.zig b/build.zig index b91fb7f..fcf6260 100644 --- a/build.zig +++ b/build.zig @@ -1,156 +1,41 @@ const std = @import("std"); -// Although this function looks imperative, it does not perform the build -// directly and instead it mutates the build graph (`b`) that will be then -// executed by an external runner. The functions in `std.Build` implement a DSL -// for defining build steps and express dependencies between them, allowing the -// build runner to parallelize the build automatically (and the cache system to -// know when a step doesn't need to be re-run). pub fn build(b: *std.Build) void { - // Standard target options allow the person running `zig build` to choose - // what target to build for. Here we do not override the defaults, which - // means any target is allowed, and the default is native. Other options - // for restricting supported target set are available. const target = b.standardTargetOptions(.{}); - // Standard optimization options allow the person running `zig build` to select - // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not - // set a preferred release mode, allowing the user to decide how to optimize. + const optimize = b.standardOptimizeOption(.{}); - // It's also possible to define more custom flags to toggle optional features - // of this build script using `b.option()`. All defined flags (including - // target and optimize options) will be listed when running `zig build --help` - // in this directory. - // This creates a module, which represents a collection of source files alongside - // some compilation options, such as optimization mode and linked system libraries. - // Zig modules are the preferred way of making Zig code available to consumers. - // addModule defines a module that we intend to make available for importing - // to our consumers. We must give it a name because a Zig package can expose - // multiple modules and consumers will need to be able to specify which - // module they want to access. - const mod = b.addModule("_2048zig", .{ - // The root source file is the "entry point" of this module. Users of - // this module will only be able to access public declarations contained - // in this file, which means that if you have declarations that you - // intend to expose to consumers that were defined in other files part - // of this module, you will have to make sure to re-export them from - // the root file. - .root_source_file = b.path("src/root.zig"), - // Later on we'll use this module as the root module of a test executable - // which requires us to specify a target. - .target = target, - }); - - // Here we define an executable. An executable needs to have a root module - // which needs to expose a `main` function. While we could add a main function - // to the module defined above, it's sometimes preferable to split business - // logic and the CLI into two separate modules. - // - // If your goal is to create a Zig library for others to use, consider if - // it might benefit from also exposing a CLI tool. A parser library for a - // data serialization format could also bundle a CLI syntax checker, for example. - // - // If instead your goal is to create an executable, consider if users might - // be interested in also being able to embed the core functionality of your - // program in their own executable in order to avoid the overhead involved in - // subprocessing your CLI tool. - // - // If neither case applies to you, feel free to delete the declaration you - // don't need and to put everything under a single module. const exe = b.addExecutable(.{ .name = "_2048zig", .root_module = b.createModule(.{ - // b.createModule defines a new module just like b.addModule but, - // unlike b.addModule, it does not expose the module to consumers of - // this package, which is why in this case we don't have to give it a name. .root_source_file = b.path("src/main.zig"), - // Target and optimization levels must be explicitly wired in when - // defining an executable or library (in the root module), and you - // can also hardcode a specific target for an executable or library - // definition if desireable (e.g. firmware for embedded devices). + .target = target, .optimize = optimize, - // List of modules available for import in source files part of the - // root module. - .imports = &.{ - // Here "_2048zig" is the name you will use in your source code to - // import this module (e.g. `@import("_2048zig")`). The name is - // repeated because you are allowed to rename your imports, which - // can be extremely useful in case of collisions (which can happen - // importing modules from different packages). - .{ .name = "_2048zig", .module = mod }, - }, + + .imports = &.{}, }), }); - // This declares intent for the executable to be installed into the - // install prefix when running `zig build` (i.e. when executing the default - // step). By default the install prefix is `zig-out/` but can be overridden - // by passing `--prefix` or `-p`. b.installArtifact(exe); - // This creates a top level step. Top level steps have a name and can be - // invoked by name when running `zig build` (e.g. `zig build run`). - // This will evaluate the `run` step rather than the default step. - // For a top level step to actually do something, it must depend on other - // steps (e.g. a Run step, as we will see in a moment). const run_step = b.step("run", "Run the app"); - // This creates a RunArtifact step in the build graph. A RunArtifact step - // invokes an executable compiled by Zig. Steps will only be executed by the - // runner if invoked directly by the user (in the case of top level steps) - // or if another step depends on it, so it's up to you to define when and - // how this Run step will be executed. In our case we want to run it when - // the user runs `zig build run`, so we create a dependency link. const run_cmd = b.addRunArtifact(exe); run_step.dependOn(&run_cmd.step); - // By making the run step depend on the default step, it will be run from the - // installation directory rather than directly from within the cache directory. run_cmd.step.dependOn(b.getInstallStep()); - // This allows the user to pass arguments to the application in the build - // command itself, like this: `zig build run -- arg1 arg2 etc` if (b.args) |args| { run_cmd.addArgs(args); } - // Creates an executable that will run `test` blocks from the provided module. - // Here `mod` needs to define a target, which is why earlier we made sure to - // set the releative field. - const mod_tests = b.addTest(.{ - .root_module = mod, - }); - - // A run step that will run the test executable. - const run_mod_tests = b.addRunArtifact(mod_tests); - - // Creates an executable that will run `test` blocks from the executable's - // root module. Note that test executables only test one module at a time, - // hence why we have to create two separate ones. const exe_tests = b.addTest(.{ .root_module = exe.root_module, }); - // A run step that will run the second test executable. const run_exe_tests = b.addRunArtifact(exe_tests); - // A top level step for running all tests. dependOn can be called multiple - // times and since the two run steps do not depend on one another, this will - // make the two of them run in parallel. const test_step = b.step("test", "Run tests"); - test_step.dependOn(&run_mod_tests.step); test_step.dependOn(&run_exe_tests.step); - - // Just like flags, top level steps are also listed in the `--help` menu. - // - // The Zig build system is entirely implemented in userland, which means - // that it cannot hook into private compiler APIs. All compilation work - // orchestrated by the build system will result in other Zig compiler - // subcommands being invoked with the right flags defined. You can observe - // these invocations when one fails (or you pass a flag to increase - // verbosity) to validate assumptions and diagnose problems. - // - // Lastly, the Zig build system is relatively simple and self-contained, - // and reading its source code will allow you to master it. } diff --git a/src/board.zig b/src/board.zig new file mode 100644 index 0000000..3c8227c --- /dev/null +++ b/src/board.zig @@ -0,0 +1,135 @@ +const std = @import("std"); +const Self = @This(); + +// +// FIELDS +// + +cells: [4][4]u16 = .{.{0} ** 4} ** 4, + +/// ---------------------------------------------------- +/// ---------------------------------------------------- +fn slideRowLeft(row: *[4]u16) void { + var write: usize = 0; // where the next tile should land + + // Pass 1: copy every non-zero tile to the next free slot. + // `cell` = WHAT we're carrying, `write` = WHERE it lands. + for (row) |cell| { + if (cell != 0) { + row[write] = cell; + write += 1; + } + } + + // Pass 2: everything after the last packed tile becomes 0. + for (write..4) |i| { + row[i] = 0; + } +} + +/// ---------------------------------------------------- +/// Reverses one row in place: [2,0,4,0] becomes [0,4,0,2]. +/// Only visits the first half (i < 2) — otherwise every swap +/// would be undone by a later swap. +/// ---------------------------------------------------- +fn reverse(row: *[4]u16) void { + for (0..2) |i| { + const tmp = row[i]; // remember one cup's contents + row[i] = row[3 - i]; // pour the opposite cup into this one + row[3 - i] = tmp; // pour the remembered contents back + } +} + +/// ---------------------------------------------------- +/// Slides every row to the LEFT, closing up gaps. +/// ---------------------------------------------------- +pub fn slideLeft(self: *Self) void { + // &self.cells = iterate the REAL grid (not a copy), + // |*row| = each row by pointer, so edits stick. + for (&self.cells) |*row| { + slideRowLeft(row); // "hey, slide THIS row" + } +} + +/// ---------------------------------------------------- +/// Slides RIGHT = mirror trick: flip each row, slide left, +/// flip back. What was "toward index 0" becomes "toward index 3". +/// ---------------------------------------------------- +pub fn slideRight(self: *Self) void { + for (&self.cells) |*row| { + reverse(row); + slideRowLeft(row); + reverse(row); + } +} + +/// ---------------------------------------------------- +/// Slides UP: pull each COLUMN out into a temp row, slide it, +/// push it back. In the temp array "left" means "toward row 0", +/// which is exactly UP on the board. +/// ---------------------------------------------------- +pub fn slideUp(self: *Self) void { + for (0..4) |c| { // c = column number + var tmp: [4]u16 = undefined; + + for (0..4) |r| tmp[r] = self.cells[r][c]; // pull column out (top→bottom) + slideRowLeft(&tmp); // slide toward top + for (0..4) |r| self.cells[r][c] = tmp[r]; // push back in + } +} + +/// ---------------------------------------------------- +/// Slides DOWN: same as slideUp, but read/write the column +/// BOTTOM→top using `3 - r`. The flip makes "toward index 0" +/// in the temp array mean DOWN on the board. +/// ---------------------------------------------------- +pub fn slideDown(self: *Self) void { + for (0..4) |c| { // c = column number + var tmp: [4]u16 = undefined; + + for (0..4) |r| tmp[r] = self.cells[3 - r][c]; // pull column out (bottom→top) + slideRowLeft(&tmp); // slide toward index 0... + for (0..4) |r| self.cells[3 - r][c] = tmp[r]; // ...which is the bottom, thanks to the flip + } +} + +/// ---------------------------------------------------- +/// Spawns a new tile (2 or 4) in a random empty cell. +/// ---------------------------------------------------- +pub fn spawn(self: *Self, rand: std.Random) void { + // --- Phase 1: find every empty cell ------------------- + // Roll 0..9 once now; we'll use it at the end to decide + // 2 vs 4 (a 1-in-10 chance of a 4, like the real game). + const n = rand.intRangeAtMost(usize, 0, 9); + + // Fixed-size shelf for cell indexes. The board has at most + // 16 empties, so no dynamic memory is ever needed. + var empties: [16]usize = undefined; + var count: usize = 0; // how many slots of `empties` we filled + + // Walk all 16 cells. Flat index i maps to the grid as: + // row = i / 4, col = i % 4 + for (0..16) |i| { + if (self.cells[i / 4][i % 4] == 0) { + empties[count] = i; // remember WHERE an empty is + count += 1; + } + } + + // Self full → nothing to spawn into, just leave. + if (count == 0) { + return; + } + + // --- Phase 2: pick one empty and fill it -------------- + const pick = rand.uintLessThan(usize, count); // random 0..count-1 + const spot = empties[pick]; // flat index of the chosen cell + + const row = spot / 4; // undo the flat-index trick + const col = spot % 4; + + var value: u16 = 2; // usually spawn a 2... + if (n == 9) value = 4; // ...but our early roll said 9 → lucky 4 + + self.cells[row][col] = value; +} diff --git a/src/game.zig b/src/game.zig deleted file mode 100644 index 64ec762..0000000 --- a/src/game.zig +++ /dev/null @@ -1,123 +0,0 @@ -//! game.zig — the 2048 board and everything it can do. -const std = @import("std"); - -/// The 4x4 playing grid. A cell holds the tile VALUE directly: -/// 0 means "empty", anything else is the number shown on screen. -pub const Board = struct { - cells: [4][4]u16 = .{.{0} ** 4} ** 4, - - /// THE core algorithm: slides ONE row left, closing gaps. - /// (Merging equal tiles will be added here later.) - /// Used by every direction — right/up/down are just disguises. - fn slideRowLeft(row: *[4]u16) void { - var write: usize = 0; // where the next tile should land - - // Pass 1: copy every non-zero tile to the next free slot. - // `cell` = WHAT we're carrying, `write` = WHERE it lands. - for (row) |cell| { - if (cell != 0) { - row[write] = cell; - write += 1; - } - } - - // Pass 2: everything after the last packed tile becomes 0. - for (write..4) |i| { - row[i] = 0; - } - } - - /// Reverses one row in place: [2,0,4,0] becomes [0,4,0,2]. - /// Only visits the first half (i < 2) — otherwise every swap - /// would be undone by a later swap. - fn reverse(row: *[4]u16) void { - for (0..2) |i| { - const tmp = row[i]; // remember one cup's contents - row[i] = row[3 - i]; // pour the opposite cup into this one - row[3 - i] = tmp; // pour the remembered contents back - } - } - - /// Slides every row to the LEFT, closing up gaps. - pub fn slideLeft(self: *Board) void { - // &self.cells = iterate the REAL grid (not a copy), - // |*row| = each row by pointer, so edits stick. - for (&self.cells) |*row| { - slideRowLeft(row); // "hey, slide THIS row" - } - } - - /// Slides RIGHT = mirror trick: flip each row, slide left, - /// flip back. What was "toward index 0" becomes "toward index 3". - pub fn slideRight(self: *Board) void { - for (&self.cells) |*row| { - reverse(row); - slideRowLeft(row); - reverse(row); - } - } - - /// Slides UP: pull each COLUMN out into a temp row, slide it, - /// push it back. In the temp array "left" means "toward row 0", - /// which is exactly UP on the board. - pub fn slideUp(self: *Board) void { - for (0..4) |c| { // c = column number - var tmp: [4]u16 = undefined; - - for (0..4) |r| tmp[r] = self.cells[r][c]; // pull column out (top→bottom) - slideRowLeft(&tmp); // slide toward top - for (0..4) |r| self.cells[r][c] = tmp[r]; // push back in - } - } - - /// Slides DOWN: same as slideUp, but read/write the column - /// BOTTOM→top using `3 - r`. The flip makes "toward index 0" - /// in the temp array mean DOWN on the board. - pub fn slideDown(self: *Board) void { - for (0..4) |c| { // c = column number - var tmp: [4]u16 = undefined; - - for (0..4) |r| tmp[r] = self.cells[3 - r][c]; // pull column out (bottom→top) - slideRowLeft(&tmp); // slide toward index 0... - for (0..4) |r| self.cells[3 - r][c] = tmp[r]; // ...which is the bottom, thanks to the flip - } - } - /// Spawns a new tile (2 or 4) in a random empty cell. - pub fn spawn(self: *Board, rand: std.Random) void { - // --- Phase 1: find every empty cell ------------------- - // Roll 0..9 once now; we'll use it at the end to decide - // 2 vs 4 (a 1-in-10 chance of a 4, like the real game). - const n = rand.intRangeAtMost(usize, 0, 9); - - // Fixed-size shelf for cell indexes. The board has at most - // 16 empties, so no dynamic memory is ever needed. - var empties: [16]usize = undefined; - var count: usize = 0; // how many slots of `empties` we filled - - // Walk all 16 cells. Flat index i maps to the grid as: - // row = i / 4, col = i % 4 - for (0..16) |i| { - if (self.cells[i / 4][i % 4] == 0) { - empties[count] = i; // remember WHERE an empty is - count += 1; - } - } - - // Board full → nothing to spawn into, just leave. - if (count == 0) { - return; - } - - // --- Phase 2: pick one empty and fill it -------------- - const pick = rand.uintLessThan(usize, count); // random 0..count-1 - const spot = empties[pick]; // flat index of the chosen cell - - const row = spot / 4; // undo the flat-index trick - const col = spot % 4; - - var value: u16 = 2; // usually spawn a 2... - if (n == 9) value = 4; // ...but our early roll said 9 → lucky 4 - - self.cells[row][col] = value; - } -}; diff --git a/src/main.zig b/src/main.zig index 2f243a4..ae9279b 100644 --- a/src/main.zig +++ b/src/main.zig @@ -1,10 +1,9 @@ //! main.zig — program entry point: sets up a board and shows it. -const game = @import("game.zig"); +const Board = @import("board.zig"); const std = @import("std"); pub fn main() !void { - // `var` (not const) because the board changes during play. - var board: game.Board = .{}; + var board: Board = .{}; // Random number generator. The seed (42) makes every run // identical for now — handy for debugging, we'll fix it later. @@ -13,21 +12,15 @@ pub fn main() !void { board.spawn(rand); // drop one starting tile onto the board - // --- TEMPORARY test setup --------------------------------- - // Hand-made rows to check the slide functions while we build. - // Once the real game loop exists, this block gets deleted and - // the board starts empty (two spawned tiles, like real 2048). board.cells[0] = .{ 2, 0, 2, 0 }; board.cells[1] = .{ 0, 4, 4, 0 }; board.cells[2] = .{ 2, 2, 2, 2 }; board.cells[3] = .{ 0, 2, 0, 4 }; board.slideUp(); // ← swap in any direction to test it - // Print the grid row by row. `{d:4}` = decimal, 4 chars wide, - // so the columns line up. for (board.cells) |row| { for (row) |cell| { - std.debug.print("{d:4}", .{cell}); + std.debug.print("\x1b[31m{d:4}", .{cell}); } std.debug.print("\n", .{}); } diff --git a/src/root.zig b/src/root.zig deleted file mode 100644 index 5a71250..0000000 --- a/src/root.zig +++ /dev/null @@ -1,18 +0,0 @@ -//! By convention, root.zig is the root source file when making a package. -const std = @import("std"); -const Io = std.Io; - -/// This is a documentation comment to explain the `printAnotherMessage` function below. -/// -/// Accepting an `Io.Writer` instance is a handy way to write reusable code. -pub fn printAnotherMessage(writer: *Io.Writer) Io.Writer.Error!void { - try writer.print("Run `zig build test` to run the tests.\n", .{}); -} - -pub fn add(a: i32, b: i32) i32 { - return a + b; -} - -test "basic add functionality" { - try std.testing.expect(add(3, 7) == 10); -} diff --git a/zig-out/bin/_2048zig b/zig-out/bin/_2048zig index 3c8109b..dda88d0 100755 Binary files a/zig-out/bin/_2048zig and b/zig-out/bin/_2048zig differ