Switched parameter order for Impl to improve clarity

permutationlock · Nov 28, 2023 · dac2f07 · dac2f07
1 parent ef377d0
commit dac2f07
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Showing 8 changed files with 44 additions and 49 deletions.
diff --git a/README.md b/README.md
@@ -8,7 +8,7 @@ The `zimpl` module is ~30 lines of code and exposes one public
 declaration: `Impl`.
 
 ```Zig
-pub fn Impl(comptime T: type, comptime Ifc: fn (type) type) type { ... }
+pub fn Impl(comptime Ifc: fn (type) type, comptime T: type) type { ... }
 ```
 
 ## Arguments
@@ -25,7 +25,7 @@ wrapping a type, e.g. `Unwrap(!?*u32)` is `u32`.
 
 ## Return value
 
-The type `Impl(T, Ifc)` is a struct type with the same fields
+The type `Impl(Ifc, T)` is a struct type with the same fields
 as `Ifc(T)`, but with the default value of each field set equal to
 the declaration of `Unwrap(T)` of the same name, if such a declaration
 exists.
@@ -45,23 +45,23 @@ pub fn Reader(comptime T: type) type {
 pub const io = struct {
     pub inline fn read(
         reader_ctx: anytype,
-        reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+        reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
         buffer: []u8,
     ) reader_impl.ReadError!usize {
         return @errorCast(reader_impl.read(reader_ctx, buffer));
     }
 
     pub inline fn readAll(
         reader_ctx: anytype,
-        reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+        reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
         buffer: []u8,
     ) reader_impl.ReadError!usize {
         return readAtLeast(reader_ctx, reader_impl, buffer, buffer.len);
     }
 
     pub inline fn readAtLeast(
         reader_ctx: anytype,
-        reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+        reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
         buffer: []u8,
         len: usize,
     ) reader_impl.ReadError!usize {

diff --git a/examples/count.zig b/examples/count.zig
@@ -1,9 +1,7 @@
 const std = @import("std");
 const testing = std.testing;
 
-const zimpl = @import("zimpl");
-const Impl = zimpl.Impl;
-const PtrChild = zimpl.PtrChild;
+const Impl = @import("zimpl").Impl;
 
 fn Counter(comptime T: type) type {
     return struct {
@@ -14,7 +12,7 @@ fn Counter(comptime T: type) type {
 
 pub fn countToTen(
     ctr_ctx: anytype,
-    comptime ctr_impl: Impl(@TypeOf(ctr_ctx), Counter),
+    ctr_impl: Impl(Counter, @TypeOf(ctr_ctx)),
 ) void {
     while (ctr_impl.read(ctr_ctx) < 10) {
         ctr_impl.increment(ctr_ctx);

diff --git a/examples/io.zig b/examples/io.zig
@@ -3,8 +3,7 @@ const native_endian = @import("builtin").target.cpu.arch.endian();
 const mem = std.mem;
 const assert = std.debug.assert;
 
-const zimpl = @import("zimpl");
-const Impl = zimpl.Impl;
+const Impl = @import("zimpl").Impl;
 
 pub const FixedBufferReader = @import("io/FixedBufferReader.zig");
 pub const FixedBufferStream = @import("io/FixedBufferStream.zig");
@@ -32,23 +31,23 @@ pub fn Reader(comptime T: type) type {
 
 pub inline fn read(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     buffer: []u8,
 ) reader_impl.ReadError!usize {
     return @errorCast(reader_impl.read(reader_ctx, buffer));
 }
 
 pub inline fn readAll(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     buffer: []u8,
 ) reader_impl.ReadError!usize {
     return readAtLeast(reader_ctx, reader_impl, buffer, buffer.len);
 }
 
 pub inline fn readAtLeast(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     buffer: []u8,
     len: usize,
 ) reader_impl.ReadError!usize {
@@ -64,7 +63,7 @@ pub inline fn readAtLeast(
 
 pub inline fn readNoEof(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     buf: []u8,
 ) (reader_impl.ReadError || error{EndOfStream})!void {
     const amt_read = try readAll(reader_ctx, reader_impl, buf);
@@ -73,9 +72,9 @@ pub inline fn readNoEof(
 
 pub inline fn streamUntilDelimiter(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     delimiter: u8,
     optional_max_size: ?usize,
 ) (reader_impl.ReadError || writer_impl.WriteError || error{
@@ -102,7 +101,7 @@ pub inline fn streamUntilDelimiter(
 
 pub inline fn skipUntilDelimiterOrEof(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     delimiter: u8,
 ) reader_impl.ReadError!void {
     while (true) {
@@ -116,7 +115,7 @@ pub inline fn skipUntilDelimiterOrEof(
 
 pub inline fn readByte(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
 ) (reader_impl.ReadError || error{EndOfStream})!u8 {
     var result: [1]u8 = undefined;
     const amt_read = try read(reader_ctx, reader_impl, result[0..]);
@@ -126,14 +125,14 @@ pub inline fn readByte(
 
 pub inline fn readByteSigned(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
 ) (reader_impl.ReadError || error{EndOfStream})!i8 {
     return @as(i8, @bitCast(try readByte(reader_ctx, reader_impl)));
 }
 
 pub inline fn readBytesNoEof(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime num_bytes: usize,
 ) (reader_impl.ReadError || error{EndOfStream})![num_bytes]u8 {
     var bytes: [num_bytes]u8 = undefined;
@@ -143,7 +142,7 @@ pub inline fn readBytesNoEof(
 
 pub inline fn readInt(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime T: type,
     endian: std.builtin.Endian,
 ) (reader_impl.ReadError || error{EndOfStream})!T {
@@ -157,7 +156,7 @@ pub inline fn readInt(
 
 pub inline fn readVarInt(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime ReturnType: type,
     endian: std.builtin.Endian,
     size: usize,
@@ -171,7 +170,7 @@ pub inline fn readVarInt(
 
 pub inline fn skipBytes(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     num_bytes: u64,
     comptime options: struct {
         buf_size: usize = 512,
@@ -189,7 +188,7 @@ pub inline fn skipBytes(
 
 pub inline fn isBytes(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     slice: []const u8,
 ) (reader_impl.ReadError || error{EndOfStream})!bool {
     var i: usize = 0;
@@ -204,7 +203,7 @@ pub inline fn isBytes(
 
 pub inline fn readStruct(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime T: type,
 ) (reader_impl.ReadError || error{EndOfStream})!T {
     // Only extern and packed structs have defined in-memory layout.
@@ -216,7 +215,7 @@ pub inline fn readStruct(
 
 pub inline fn readStructBig(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime T: type,
 ) (reader_impl.ReadError || error{EndOfStream})!T {
     var res = try readStruct(reader_ctx, reader_impl, T);
@@ -228,7 +227,7 @@ pub inline fn readStructBig(
 
 pub inline fn readEnum(
     reader_ctx: anytype,
-    reader_impl: Impl(@TypeOf(reader_ctx), Reader),
+    reader_impl: Impl(Reader, @TypeOf(reader_ctx)),
     comptime Enum: type,
     endian: std.builtin.Endian,
 ) (reader_impl.ReadError || error{ EndOfStream, InvalidValue })!Enum {
@@ -263,15 +262,15 @@ pub fn Writer(comptime T: type) type {
 
 pub fn write(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     bytes: []const u8,
 ) writer_impl.WriteError!usize {
     return @errorCast(writer_impl.write(writer_ctx, bytes));
 }
 
 pub fn writeAll(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     bytes: []const u8,
 ) writer_impl.WriteError!void {
     var index: usize = 0;
@@ -282,7 +281,7 @@ pub fn writeAll(
 
 pub fn writeByte(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     byte: u8,
 ) writer_impl.WriteError!void {
     const array = [1]u8{byte};
@@ -291,7 +290,7 @@ pub fn writeByte(
 
 pub fn writeByteNTimes(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     byte: u8,
     n: usize,
 ) writer_impl.WriteError!void {
@@ -308,7 +307,7 @@ pub fn writeByteNTimes(
 
 pub inline fn writeInt(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     comptime T: type,
     value: T,
     endian: std.builtin.Endian,
@@ -325,7 +324,7 @@ pub inline fn writeInt(
 
 pub fn writeStruct(
     writer_ctx: anytype,
-    writer_impl: Impl(@TypeOf(writer_ctx), Writer),
+    writer_impl: Impl(Writer, @TypeOf(writer_ctx)),
     value: anytype,
 ) writer_impl.WriteError!void {
     // Only extern and packed structs have defined in-memory layout.
@@ -349,30 +348,30 @@ pub fn Seekable(comptime T: type) type {
 
 pub fn seekTo(
     seek_ctx: anytype,
-    seek_impl: Impl(@TypeOf(seek_ctx), Seekable),
+    seek_impl: Impl(Seekable, @TypeOf(seek_ctx)),
     pos: u64,
 ) seek_impl.SeekError!void {
     return @errorCast(seek_impl.seekTo(seek_ctx, pos));
 }
 
 pub fn seekBy(
     seek_ctx: anytype,
-    seek_impl: Impl(@TypeOf(seek_ctx), Seekable),
+    seek_impl: Impl(Seekable, @TypeOf(seek_ctx)),
     amt: i64,
 ) seek_impl.SeekError!void {
     return @errorCast(seek_impl.seekBy(seek_ctx, amt));
 }
 
 pub fn getPos(
     seek_ctx: anytype,
-    seek_impl: Impl(@TypeOf(seek_ctx), Seekable),
+    seek_impl: Impl(Seekable, @TypeOf(seek_ctx)),
 ) seek_impl.GetSeekPosError!u64 {
     return @errorCast(seek_impl.getPos(seek_ctx));
 }
 
 pub fn getEndPos(
     seek_ctx: anytype,
-    seek_impl: Impl(@TypeOf(seek_ctx), Seekable),
+    seek_impl: Impl(Seekable, @TypeOf(seek_ctx)),
 ) seek_impl.GetSeekPosError!u64 {
     return @errorCast(seek_impl.getEndPos(seek_ctx));
 }

diff --git a/examples/io/counting_writer.zig b/examples/io/counting_writer.zig
@@ -1,14 +1,13 @@
 const std = @import("std");
 const testing = std.testing;
 
-const zimpl = @import("zimpl");
-const Impl = zimpl.Impl;
+const Impl = @import("zimpl").Impl;
 
 const io = @import("../io.zig");
 
 pub fn CountingWriter(
     comptime ChildCtx: type,
-    comptime child_impl: Impl(ChildCtx, io.Writer),
+    comptime child_impl: Impl(io.Writer, ChildCtx),
 ) type {
     return struct {
         child_ctx: ChildCtx,
@@ -26,7 +25,7 @@ pub fn CountingWriter(
 
 pub fn countingWriter(
     child_ctx: anytype,
-    child_impl: Impl(@TypeOf(child_ctx), io.Writer),
+    child_impl: Impl(io.Writer, @TypeOf(child_ctx)),
 ) CountingWriter(@TypeOf(child_ctx), child_impl) {
     return .{ .child_ctx = child_ctx };
 }

diff --git a/examples/iterator.zig b/examples/iterator.zig
@@ -1,8 +1,7 @@
 const std = @import("std");
 const testing = std.testing;
 
-const zimpl = @import("zimpl");
-const Impl = zimpl.Impl;
+const Impl = @import("zimpl").Impl;
 
 fn Iterator(comptime Data: type) fn (type) type {
     return struct {
@@ -18,7 +17,7 @@ pub fn apply(
     comptime T: type,
     comptime f: fn (*T) void,
     iter: anytype,
-    impl: Impl(@TypeOf(iter), Iterator(T)),
+    impl: Impl(Iterator(T), @TypeOf(iter)),
 ) void {
     var mut_iter = iter;
     while (impl.next(&mut_iter)) |t| {

diff --git a/examples/read_file.zig b/examples/read_file.zig
@@ -20,7 +20,7 @@ test "read file with std.os.fd_t" {
         std.os.O.RDONLY,
         0,
     );
-    const fd_reader: Impl(std.os.fd_t, io.Reader) = .{
+    const fd_reader: Impl(io.Reader, std.os.fd_t) = .{
         .read = std.os.read,
         .ReadError = std.os.ReadError,
     };

diff --git a/src/zimpl.zig b/src/zimpl.zig
@@ -1,6 +1,6 @@
 const Type = @import("std").builtin.Type;
 
-pub fn Impl(comptime T: type, comptime Ifc: fn (type) type) type {
+pub fn Impl(comptime Ifc: fn (type) type, comptime T: type) type {
     switch (@typeInfo(Unwrap(T))) {
         .Struct, .Union, .Enum, .Opaque => {},
         else => return Ifc(T),

diff --git a/why.md b/why.md
@@ -140,7 +140,7 @@ const Server = struct {
     pub fn poll(
         self: *Self,
         handler_ctx: anytype,
-        handler_impl: Impl(@TypeOf(handler_ctx), Handler)
+        handler_impl: Impl(Handler, @TypeOf(handler_ctx))
     ) void {
         try self.pollSockets();
         while (self.getEvent()) |evt| {
@@ -159,7 +159,7 @@ var server = Server{};
 var handler = MyHandler{};
 try server.listen(8080);
 while (true) {
-    // Impl(*MyHandler, Handler) can be default constructed because MyHandler
+    // Impl(Handler, *MyHandler) can be default constructed because MyHandler
     // has onOpen, onMessage, and onClose member functions
     try server.poll(&handler, .{});
 }