feat: 1.2.2: Display /w activity

.gitignore

@@ -0,0 +1,2 @@
+*/target/
+target/

1-hello-world/formatted-printing/display/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "deisplay"
+version = "0.1.0"

1-hello-world/formatted-printing/display/src/main.rs

@@ -1,3 +1,111 @@
-fn main() {
-    println!("Hello, world!");
+// Import (via `use`) the `fmt` module to make it available.
+use std::fmt;
+
+// Define a structure for which `fmt::Display` will be implemented. This is
+// a tuple struct named `Structure` that contains an `i32`.
+#[derive(Debug)]
+struct Structure(i32);
+
+// To use the `{}` marker, the trait `fmt::Display` must be implemented
+// manually for the type.
+impl fmt::Display for Structure {
+    // This trait requires `fmt` with this exact signature.
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Write strictly the first element into the supplied output
+        // stream: `f`. Returns `fmt::Result` which indicates whether the
+        // operation succeeded or failed. Note that `write!` uses syntax which
+        // is very similar to `println!`.
+        write!(f, "S[i32] => {}", self.0)
+    }
 }
+
+// ======================================================
+
+// A structure holding two numbers. `Debug` will be derived so the results can
+// be contrasted with `Display`.
+#[derive(Debug)]
+struct MinMax(i64, i64);
+
+// Implement `Display` for `MinMax`.
+impl fmt::Display for MinMax {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Use `self.number` to refer to each positional data point.
+        write!(f, "({}, {})", self.0, self.1)
+    }
+}
+
+// Define a structure where the fields are nameable for comparison.
+#[derive(Debug)]
+struct Point2D {
+    x: f64,
+    y: f64,
+}
+
+// Similarly, implement `Display` for `Point2D`.
+impl fmt::Display for Point2D {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Customize so only `x` and `y` are denoted.
+        write!(f, "x: {}, y: {}", self.x, self.y)
+    }
+}
+
+// ======================================================
+
+#[derive(Debug)]
+struct Complex {
+    r: f64,
+    i: f64,
+}
+
+impl fmt::Display for Complex {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.i < 0_f64 {
+            return write!(f, "{r} | - {i}i", r = self.r, i = self.i.abs());
+        }
+        return write!(f, "{r} | + {i}i", r = self.r, i = self.i);
+    }
+}
+
+fn main() {
+    // Note that we use `{}` - which is "normal displaying"
+    println!("Structure {} will print!", Structure(7));
+
+    // ======================================================
+
+    let minmax = MinMax(0, 14);
+
+    println!("Compare structures:");
+    println!("Display: {}", minmax);
+    println!("Debug: {:?}", minmax);
+
+    let big_range =   MinMax(-300, 300);
+    let small_range = MinMax(-3, 3);
+
+    println!("The big range is {big} and the small is {small}",
+        small = small_range,
+        big = big_range);
+
+    let point = Point2D { x: 3.3, y: 7.2 };
+
+    println!("Compare points:");
+    println!("Display: {}", point);
+    println!("Debug: {:?}", point);
+
+    // The following line would not compile: both `Debug` and `Display`
+    // were implemented, but `{:b}` requires `fmt::Binary` to be
+    // implemented, which it hasn't been for `Point2D`.
+    // println!("What does Point2D look like in binary: {:b}?", point);
+    //
+    let positive_complex = Complex{ r : 3.3_f64, i : 7.2_f64 };
+    let negative_complex = Complex{ r : 3.3_f64, i : -7.2_f64 };
+
+    println!("Compare complex:");
+    println!("Display: {}", positive_complex);
+    println!("Debug: {:?}", positive_complex);
+
+    println!("Compare complex:");
+    println!("Display: {}", negative_complex);
+    println!("Debug: {:?}", negative_complex);
+}
+
+

1-hello-world/formatted-printing/display/target/.rustc_info.json

@@ -0,0 +1 @@
+{"rustc_fingerprint":14802351894921902018,"outputs":{"1847801304416329599":{"success":true,"status":"","code":0,"stdout":"rustc 1.98.1 (48a229cea 2026-09-01)\nbinary: rustc\ncommit-hash: 48a229ceaefd4985c50990b14116b6d856af0985\ncommit-date: 2026-09-01\nhost: x86_64-unknown-linux-gnu\nrelease: 1.98.1\nLLVM version: 22.1.8\n","stderr":""},"7971740275564407648":{"success":true,"status":"","code":0,"stdout":"___\nlib___.rlib\nlib___.so\nlib___.so\nlib___.a\nlib___.so\n/home/nak/.rustup/toolchains/stable-x86_64-unknown-linux-gnu\noff\npacked\nunpacked\n___\ndebug_assertions\npanic=\"unwind\"\nproc_macro\ntarget_abi=\"\"\ntarget_arch=\"x86_64\"\ntarget_endian=\"little\"\ntarget_env=\"gnu\"\ntarget_family=\"unix\"\ntarget_feature=\"fxsr\"\ntarget_feature=\"sse\"\ntarget_feature=\"sse2\"\ntarget_has_atomic=\"16\"\ntarget_has_atomic=\"32\"\ntarget_has_atomic=\"64\"\ntarget_has_atomic=\"8\"\ntarget_has_atomic=\"ptr\"\ntarget_has_atomic_primitive_alignment=\"16\"\ntarget_has_atomic_primitive_alignment=\"32\"\ntarget_has_atomic_primitive_alignment=\"64\"\ntarget_has_atomic_primitive_alignment=\"8\"\ntarget_has_atomic_primitive_alignment=\"ptr\"\ntarget_os=\"linux\"\ntarget_pointer_width=\"64\"\ntarget_vendor=\"unknown\"\nunix\n","stderr":""}},"successes":{}}

1-hello-world/formatted-printing/display/target/CACHEDIR.TAG

@@ -0,0 +1,3 @@
+Signature: 8a477f597d28d172789f06886806bc55
+# This file is a cache directory tag created by cargo.
+# For information about cache directory tags see https://bford.info/cachedir/

1-hello-world/formatted-printing/display/target/debug/.fingerprint/deisplay-80701de140c8cedd/bin-deisplay

@@ -0,0 +1 @@
+e0bf6de377ff0135

1-hello-world/formatted-printing/display/target/debug/.fingerprint/deisplay-80701de140c8cedd/bin-deisplay.json

@@ -0,0 +1 @@
+{"rustc":1625334936438085654,"features":"[]","declared_features":"[]","target":9871736305712052871,"profile":8731458305071235362,"path":4942398508502643691,"deps":[],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/deisplay-80701de140c8cedd/dep-bin-deisplay","checksum":false}}],"rustflags":[],"config":9396254390672932401,"compile_kind":0}

1-hello-world/formatted-printing/display/target/debug/.fingerprint/deisplay-80701de140c8cedd/invoked.timestamp

@@ -0,0 +1 @@
+This file has an mtime of when this was started.

1-hello-world/formatted-printing/display/target/debug/deisplay.d

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+/home/nak/Code/rust/learn-rust/1-hello-world/formatted-printing/display/target/debug/deisplay: /home/nak/Code/rust/learn-rust/1-hello-world/formatted-printing/display/src/main.rs

1-hello-world/formatted-printing/display/target/debug/deps/deisplay-80701de140c8cedd.d

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+/home/nak/Code/rust/learn-rust/1-hello-world/formatted-printing/display/target/debug/deps/deisplay-80701de140c8cedd.d: src/main.rs
+
+/home/nak/Code/rust/learn-rust/1-hello-world/formatted-printing/display/target/debug/deps/deisplay-80701de140c8cedd: src/main.rs
+
+src/main.rs: