diff --git a/src/bmp_valid.zig b/src/bmp_valid.zig
index c4f9438..6468658 100644
--- a/src/bmp_valid.zig
+++ b/src/bmp_valid.zig
@@ -20,7 +20,7 @@ pub fn magicValid(magic: []const u8) !void {
     }
 
     if (!valid) {
-        std.debug.warn("\tINVALID HEADER: '{}'\n", .{magic});
+        std.debug.warn("\tINVALID HEADER: '{s}'\n", .{magic});
         return BMPValidError.InvalidMagic;
     }
 }
diff --git a/src/custom.zig b/src/custom.zig
index e1a9107..03120f0 100644
--- a/src/custom.zig
+++ b/src/custom.zig
@@ -174,7 +174,7 @@ pub const Embed = struct {
 
         if (read_bytes < 0) {
             const st: i32 = c.sf_error(self.sndfile);
-            std.debug.warn("Failed to read {} ({})\n", .{
+            std.debug.warn("Failed to read {s} ({s})\n", .{
                 self.filepath,
                 c.sf_error_number(st),
             });
diff --git a/src/image.zig b/src/image.zig
index 32a93ec..b6e13ae 100644
--- a/src/image.zig
+++ b/src/image.zig
@@ -32,7 +32,7 @@ pub fn sopen(
     const st: i32 = c.sf_error(file);
 
     if (st != 0) {
-        std.debug.warn("Failed to open {} ({})\n", .{
+        std.debug.warn("Failed to open {s} ({s})\n", .{
             path,
             c.sf_error_number(st),
         });
@@ -181,7 +181,7 @@ pub const Image = struct {
     pub fn close(self: *Image) void {
         var st: i32 = c.sf_close(self.sndfile);
         if (st != 0) {
-            std.debug.warn("Failed to close {} ({})\n", .{
+            std.debug.warn("Failed to close {s} ({s})\n", .{
                 self.path,
                 c.sf_error_number(st),
             });
@@ -228,7 +228,7 @@ pub const Image = struct {
         sseek(out_file, start);
 
         while (i <= end) : (i += buf.len) {
-            std.debug.warn("\t\ti={}, buf.len={}, end={}\n", .{ i, buf.len, end });
+            std.debug.warn("\t\ti={d}, buf.len={d}, end={d}\n", .{ i, buf.len, end });
             sseek(self.sndfile, i);
             sseek(out_file, i);
 
@@ -254,7 +254,7 @@ pub const Image = struct {
     fn getSeekPos(self: *Image, position: plugins.Position) plugins.SeekPos {
         const file_end = self.frames;
         var seek_pos = position.seekPos(file_end);
-        std.debug.warn("\tstart {} end {}\n", .{ seek_pos.start, seek_pos.end });
+        std.debug.warn("\tstart {d} end {d}\n", .{ seek_pos.start, seek_pos.end });
         return seek_pos;
     }
 
@@ -267,7 +267,7 @@ pub const Image = struct {
         self.curpath = path;
         self.frames = @intCast(usize, in_fmt.frames);
 
-        std.debug.warn("\timage: reopened on '{}' (frames={}, fmt.frames={})\n", .{
+        std.debug.warn("\timage: reopened on '{s}' (frames={d}, fmt.frames={d})\n", .{
             self.curpath,
             self.frames,
             in_fmt.frames,
@@ -310,12 +310,12 @@ pub const Image = struct {
         defer ctx.allocator.free(ports);
 
         if (ctx.n_audio_in > 2) {
-            std.debug.warn("plugin <{}> has more than two inputs.\n", .{plugin_uri});
+            std.debug.warn("plugin <{s}> has more than two inputs.\n", .{plugin_uri});
             return ImageError.InvalidPlugin;
         }
 
         if (ctx.n_audio_out > 2) {
-            std.debug.warn("plugin <{}> has more than two outputs.\n", .{plugin_uri});
+            std.debug.warn("plugin <{s}> has more than two outputs.\n", .{plugin_uri});
             return ImageError.InvalidPlugin;
         }
 
@@ -327,14 +327,14 @@ pub const Image = struct {
 
             var sym = c.lilv_new_string(ctx.world, sym_cstr.ptr);
             const port = c.lilv_plugin_get_port_by_symbol(ctx.plugin, sym) orelse {
-                std.debug.warn("assert fail: symbol {} not found on port\n", .{param.sym});
+                std.debug.warn("assert fail: symbol {s} not found on port\n", .{param.sym});
                 return ImageError.InvalidSymbol;
             };
 
             c.lilv_node_free(sym);
 
             var idx = c.lilv_port_get_index(ctx.plugin, port);
-            std.debug.warn("\tset sym={}, idx={} to val={}\n", .{
+            std.debug.warn("\tset sym={s}, idx={d} to val={}\n", .{
                 param.sym,
                 idx,
                 param.value,
@@ -345,7 +345,7 @@ pub const Image = struct {
         // now we need to generate a temporary file and put the output of
         // running the plugin on that file
         var tmpnam = try temporaryName(self.allocator);
-        std.debug.warn("\trunning plugin from '{}' to '{}'\n", .{ self.curpath, tmpnam });
+        std.debug.warn("\trunning plugin from '{s}' to '{s}'\n", .{ self.curpath, tmpnam });
 
         var out_fmt = mkSfInfo();
         var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
@@ -378,7 +378,7 @@ pub const Image = struct {
         sseek(self.sndfile, seek_pos.start);
 
         var i: usize = seek_pos.start;
-        std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
+        std.debug.warn("\tseek pos start: {d} end: {d}\n", .{ seek_pos.start, seek_pos.end });
 
         var inbuf = &rctx.buffers.in;
         var outbuf = &rctx.buffers.out;
@@ -389,7 +389,7 @@ pub const Image = struct {
 
             const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
-                std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
+                std.debug.warn("WARN! reached EOF at idx={d}\n", .{i});
                 break;
             }
 
@@ -422,7 +422,7 @@ pub const Image = struct {
     }
 
     pub fn saveTo(self: *Image, out_path: []const u8) !void {
-        std.debug.warn("\timg: copy from '{}' to '{}'\n", .{ self.curpath, out_path });
+        std.debug.warn("\timg: copy from '{s}' to '{s}'\n", .{ self.curpath, out_path });
         try std.fs.copyFileAbsolute(self.curpath, out_path, .{});
     }
 
@@ -450,7 +450,7 @@ pub const Image = struct {
         // the code here is a copypaste of runPlugin() without the specific
         // lilv things.
         var tmpnam = try temporaryName(self.allocator);
-        std.debug.warn("\trunning CUSTOM plugin from '{}' to '{}'\n", .{ self.curpath, tmpnam });
+        std.debug.warn("\trunning CUSTOM plugin from '{s}' to '{s}'\n", .{ self.curpath, tmpnam });
 
         var out_fmt = mkSfInfo();
         var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
@@ -477,7 +477,7 @@ pub const Image = struct {
         sseek(self.sndfile, seek_pos.start);
 
         var i: usize = seek_pos.start;
-        std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
+        std.debug.warn("\tseek pos start: {d} end: {d}\n", .{ seek_pos.start, seek_pos.end });
 
         var inbuf = &bufs.in;
         var outbuf = &bufs.out;
@@ -485,7 +485,7 @@ pub const Image = struct {
         while (i <= seek_pos.end) : (i += 1) {
             const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
-                std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
+                std.debug.warn("WARN! reached EOF at idx={d}\n", .{i});
                 break;
             }
 
diff --git a/src/lang.zig b/src/lang.zig
index d5c193a..b299ae0 100644
--- a/src/lang.zig
+++ b/src/lang.zig
@@ -146,7 +146,7 @@ pub const Command = struct {
     }
 
     pub fn print(base: *const @This()) void {
-        std.debug.warn("tag: {}\n", .{base.tag});
+        std.debug.warn("tag: {s}\n", .{base.tag});
     }
 
     pub const Noop = struct {
@@ -549,7 +549,7 @@ pub const Lang = struct {
             inline for (@typeInfo(@TypeOf(cmd.parameters)).Struct.fields) |cmd_field| {
                 const maybe_arg = tok_it.next();
                 if (maybe_arg == null) {
-                    self.doError("Expected parameter for {}, got nothing", .{cmd_field.name});
+                    self.doError("Expected parameter for {s}, got nothing", .{cmd_field.name});
                     return;
                 }
 
@@ -580,7 +580,7 @@ pub const Lang = struct {
                     else => @compileError("Invalid parameter type (" ++ @typeName(cmd_field.field_type) ++ ") left on command struct " ++ @typeName(command_struct) ++ "."),
                 };
 
-                std.debug.warn("parsing {}, arg of type {} => {}\n", .{
+                std.debug.warn("parsing {s}, arg of type {s} => {any}\n", .{
                     @typeName(command_struct),
                     @typeName(@TypeOf(argument_value)),
                     argument_value,
@@ -592,7 +592,7 @@ pub const Lang = struct {
 
         cmd.base.tag = command_struct.base_tag;
         const command = cmd.base.cast(command_struct).?;
-        std.debug.warn("cmd: {}\n", .{command});
+        std.debug.warn("cmd: {s}\n", .{command});
 
         try commands.append(&cmd.base);
     }
@@ -653,7 +653,7 @@ pub const Lang = struct {
             }
 
             if (!found) {
-                self.doError("Unknown command '{}' ({})", .{ command_string, command_string.len });
+                self.doError("Unknown command '{s}' ({d} bytes)", .{ command_string, command_string.len });
                 continue;
             }
         }
diff --git a/src/lv2_helpers.zig b/src/lv2_helpers.zig
index fcfa2c9..599370c 100644
--- a/src/lv2_helpers.zig
+++ b/src/lv2_helpers.zig
@@ -118,7 +118,7 @@ pub fn setupPorts(ctx: *plugin.Context) ![]Port {
         if (c.lilv_port_is_a(ctx.plugin, lport, lv2_InputPort)) {
             port.is_input = true;
         } else if (!c.lilv_port_is_a(ctx.plugin, lport, lv2_OutputPort) and !port.optional) {
-            std.debug.warn("Port {} is neither input or output\n", .{i});
+            std.debug.warn("Port {d} is neither input or output\n", .{i});
             return error.UnassignedIOPort;
         }
 
@@ -134,7 +134,7 @@ pub fn setupPorts(ctx: *plugin.Context) ![]Port {
                 ctx.n_audio_out += 1;
             }
         } else if (!port.optional) {
-            std.debug.warn("Port {} has unsupported type\n", .{i});
+            std.debug.warn("Port {d} has unsupported type\n", .{i});
             return error.UnsupportedPortType;
         }
     }
diff --git a/src/magick.zig b/src/magick.zig
index 33ba882..dd5f295 100644
--- a/src/magick.zig
+++ b/src/magick.zig
@@ -39,7 +39,7 @@ fn magickLoad(image: *Image) !MagickContext {
     var curpath = try std.cstr.addNullByte(image.allocator, image.curpath);
     defer image.allocator.free(curpath);
 
-    std.debug.warn("loading '{}'\n", .{curpath});
+    std.debug.warn("loading '{s}'\n", .{curpath});
 
     if (mc.MagickReadImage(mctx.wand, curpath.ptr) != 1)
         return error.MagickReadFail;
@@ -54,7 +54,7 @@ fn magickSave(image: *Image, wand: *mc.MagickWand) !void {
     var c_tmpnam = try std.cstr.addNullByte(allocator, tmpnam);
     defer allocator.free(c_tmpnam);
 
-    std.debug.warn("\tmagick: saving to '{}'..", .{c_tmpnam});
+    std.debug.warn("\tmagick: saving to '{s}'..", .{c_tmpnam});
 
     if (mc.MagickWriteImage(wand, c_tmpnam.ptr) != 1)
         return error.MagickWriteFail;
diff --git a/src/main.zig b/src/main.zig
index 8ea264d..6ebe124 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -38,7 +38,7 @@ fn copyCommandToHeap(allocator: *std.mem.Allocator, command: langs.Command, comp
 
 pub fn doRepl(allocator: *std.mem.Allocator, args_it: anytype) !void {
     var stdout_file = std.io.getStdOut();
-    const stdout = &stdout_file.outStream();
+    const stdout = &stdout_file.writer();
     const scri_path = try (args_it.next(allocator) orelse @panic("expected scri path"));
 
     var file_read_opt: ?std.fs.File = std.fs.cwd().openFile(scri_path, .{}) catch |err| blk: {
@@ -95,7 +95,7 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: anytype) !void {
     });
     defer file.close();
 
-    var out = file.outStream();
+    var out = file.writer();
     var stream = &out;
 
     // since we opened the file for writing, it becomes empty, so, to ensure
diff --git a/src/plugin.zig b/src/plugin.zig
index 78e8a6d..cb8c64a 100644
--- a/src/plugin.zig
+++ b/src/plugin.zig
@@ -137,7 +137,7 @@ pub fn makeContext(allocator: *std.mem.Allocator, plugin_uri: []const u8) !Conte
     c.lilv_world_load_all(world);
 
     var uri: *c.LilvNode = c.lilv_new_uri(world, cstr_plugin_uri.ptr) orelse {
-        std.debug.warn("Invalid plugin URI <{}>\n", .{plugin_uri});
+        std.debug.warn("Invalid plugin URI <{s}>\n", .{plugin_uri});
         return ImageError.InvalidPlugin;
     };
     defer c.lilv_node_free(uri);
@@ -145,7 +145,7 @@ pub fn makeContext(allocator: *std.mem.Allocator, plugin_uri: []const u8) !Conte
     const plugins: *const c.LilvPlugins = c.lilv_world_get_all_plugins(world).?;
 
     var plugin: *const c.LilvPlugin = c.lilv_plugins_get_by_uri(plugins, uri) orelse {
-        std.debug.warn("Plugin <{}> not found\n", .{plugin_uri});
+        std.debug.warn("Plugin <{s}> not found\n", .{plugin_uri});
         return ImageError.UnknownPlugin;
     };
 
diff --git a/src/printer.zig b/src/printer.zig
index 5ea5a7b..c1fab31 100644
--- a/src/printer.zig
+++ b/src/printer.zig
@@ -3,12 +3,14 @@ const langs = @import("lang.zig");
 
 fn printCommandWithParams(stream: anytype, command: anytype) !void {
     const Parameters = @TypeOf(command.parameters);
-    try stream.print(" {} {}", .{ command.split, command.index });
+    try stream.print(" {d} {d}", .{ command.split, command.index });
     inline for (@typeInfo(Parameters).Struct.fields) |field| {
         if (field.field_type == f32 or field.field_type == f64) {
+            try stream.print(" {}", .{@field(command.parameters, field.name)});
+        } else if (field.field_type == usize or field.field_type == u64) {
             try stream.print(" {d}", .{@field(command.parameters, field.name)});
         } else {
-            try stream.print(" {}", .{@field(command.parameters, field.name)});
+            try stream.print(" {s}", .{@field(command.parameters, field.name)});
         }
     }
 }
@@ -17,12 +19,6 @@ fn printCommand(stream: anytype, cmd: *langs.Command, comptime tag: langs.Comman
     const CommandStruct = langs.Command.tagToType(tag);
     const casted = cmd.cast(CommandStruct).?;
 
-    // TODO move this to Tag method?
-    const is_typed = switch (tag) {
-        .noop, .load, .quicksave, .runqs, .rotate => false,
-        else => true,
-    };
-
     const ctype = CommandStruct.command_type;
     switch (ctype) {
         .lv2_command => try printCommandWithParams(stream, casted),
@@ -33,21 +29,21 @@ fn printCommand(stream: anytype, cmd: *langs.Command, comptime tag: langs.Comman
 pub fn printList(list: langs.CommandList, stream: anytype) !void {
     for (list.list.items) |cmd| {
         const command = @tagName(cmd.tag);
-        try stream.print("{}", .{command});
+        try stream.print("{s}", .{command});
 
         switch (cmd.tag) {
             .load => {
                 const load = cmd.cast(langs.Command.Load).?;
-                try stream.print(" {}", .{load.path});
+                try stream.print(" {s}", .{load.path});
             },
             .runqs => {
                 const runqs = cmd.cast(langs.Command.RunQS).?;
-                try stream.print(" {}", .{runqs.program});
+                try stream.print(" {s}", .{runqs.program});
             },
             .noop, .quicksave => {},
             .rotate => {
                 const rotate = cmd.cast(langs.Command.Rotate).?;
-                try stream.print(" {d} {}", .{ rotate.deg, rotate.bgfill });
+                try stream.print(" {d} {s}", .{ rotate.deg, rotate.bgfill });
             },
 
             .amp => try printCommand(stream, cmd, .amp),
diff --git a/src/runner.zig b/src/runner.zig
index a10b7a5..1bec75a 100644
--- a/src/runner.zig
+++ b/src/runner.zig
@@ -67,11 +67,10 @@ pub const Runner = struct {
             // ':0' should ALWAYS point to the image.
             if (self.repl) index += 3 else index += 2;
 
-            std.debug.warn("ARGS!! {} \n", .{self.args.len});
             for (self.args) |arg, idx| {
-                std.debug.warn("arg{} = {}\n", .{ idx, arg });
+                std.debug.warn("arg{d} = {s}\n", .{ idx, arg });
             }
-            std.debug.warn("fetch arg idx={}, val={}\n", .{ index, self.args[index] });
+            std.debug.warn("fetch arg idx={d}, val={s}\n", .{ index, self.args[index] });
             return self.args[index];
         } else {
             return load_path;
@@ -91,7 +90,7 @@ pub const Runner = struct {
 
     fn loadCmd(self: *Runner, path_or_argidx: []const u8) !void {
         const load_path = try self.resolveArgPath(path_or_argidx);
-        std.debug.warn("\tload path: {}\n", .{load_path});
+        std.debug.warn("\tload path: {s}\n", .{load_path});
 
         // we could use ImageMagick to convert from X to BMP
         // but i can't find an easy way to do things in memory.
@@ -101,7 +100,7 @@ pub const Runner = struct {
         // krita/gimp and make it export a bmp and while in the program you can
         // apply filters, etc.
         if (!std.mem.endsWith(u8, load_path, ".bmp") and !std.mem.endsWith(u8, load_path, ".ppm")) {
-            std.debug.warn("Only BMP files are allowed to be loaded. Got path '{}'\n", .{load_path});
+            std.debug.warn("Only BMP files are allowed to be loaded. Got path '{s}'\n", .{load_path});
             return RunError.NoBMP;
         }
 
@@ -138,7 +137,7 @@ pub const Runner = struct {
 
         // starts_with would be "x_g", we want to find all files in the directory
         // that start with that name.
-        const starts_with = try std.fmt.allocPrint(self.allocator, "{}_g", .{
+        const starts_with = try std.fmt.allocPrint(self.allocator, "{s}_g", .{
             basename[0..period_idx],
         });
         defer self.allocator.free(starts_with);
@@ -172,7 +171,7 @@ pub const Runner = struct {
             }
         }
 
-        const out_path = try std.fmt.allocPrint(self.allocator, "{}/{}{}{}", .{
+        const out_path = try std.fmt.allocPrint(self.allocator, "{s}/{s}{d}{s}", .{
             dirname,
             starts_with,
             max + 1,
@@ -202,7 +201,7 @@ pub const Runner = struct {
         );
         defer proc.deinit();
 
-        std.debug.warn("running '{} {}'\n", .{ runqs.program, out_path });
+        std.debug.warn("running '{s} {s}'\n", .{ runqs.program, out_path });
         _ = try proc.spawnAndWait();
     }