1 files changed, 141 insertions, 0 deletions
diff --git a/libpsi-core/src/maths/format.rs b/libpsi-core/src/maths/format.rs
new file mode 100644
index 0000000..957f1b6
--- /dev/null
+++ b/libpsi-core/src/maths/format.rs
@@ -0,0 +1,141 @@
+use crate::Complex;
+
+const EPSILON: f64 = 1e-10;
+const SQRT_2: f64 = 1.4142135623730951;
+const INV_SQRT_2: f64 = 0.7071067811865475;
+const INV_SQRT_8: f64 = 0.3535533905932738;
+const INV_SQRT_32: f64 = 0.1767766952966369;
+
+fn approx_eq(a: f64, b: f64) -> bool {
+    (a - b).abs() < EPSILON
+}
+
+fn format_real_symbolic(v: f64) -> Option<String> {
+    let abs_v = v.abs();
+    let sign = if v < 0.0 { "-" } else { "" };
+
+    if approx_eq(abs_v, 0.0) {
+        return Some("0".to_string());
+    }
+    if approx_eq(abs_v, 1.0) {
+        return Some(format!("{}1", sign));
+    }
+    if approx_eq(abs_v, 0.5) {
+        return Some(format!("{}½", sign));
+    }
+    if approx_eq(abs_v, 0.25) {
+        return Some(format!("{}¼", sign));
+    }
+    if approx_eq(abs_v, 0.75) {
+        return Some(format!("{}¾", sign));
+    }
+    if approx_eq(abs_v, 0.125) {
+        return Some(format!("{}⅛", sign));
+    }
+    if approx_eq(abs_v, SQRT_2) {
+        return Some(format!("{}√2", sign));
+    }
+    if approx_eq(abs_v, INV_SQRT_2) {
+        return Some(format!("{}¹⁄√2", sign));
+    }
+    if approx_eq(abs_v, INV_SQRT_8) {
+        return Some(format!("{}¹⁄√8", sign));
+    }
+    if approx_eq(abs_v, INV_SQRT_32) {
+        return Some(format!("{}¹⁄√32", sign));
+    }
+    if approx_eq(abs_v, 2.0) {
+        return Some(format!("{}2", sign));
+    }
+    if approx_eq(abs_v, 1.0 / 3.0) {
+        return Some(format!("{}⅓", sign));
+    }
+    if approx_eq(abs_v, 2.0 / 3.0) {
+        return Some(format!("{}⅔", sign));
+    }
+
+    None
+}
+
+pub fn format_amplitude(c: &Complex<f64>) -> String {
+    let re = c.real;
+    let im = c.imaginary;
+
+    let re_zero = approx_eq(re.abs(), 0.0);
+    let im_zero = approx_eq(im.abs(), 0.0);
+
+    if re_zero && im_zero {
+        return "0".to_string();
+    }
+
+    if im_zero {
+        if let Some(s) = format_real_symbolic(re) {
+            return s;
+        }
+        return format!("{:.4}", re);
+    }
+
+    if re_zero {
+        if approx_eq(im.abs(), 1.0) {
+            return if im > 0.0 {
+                "i".to_string()
+            } else {
+                "-i".to_string()
+            };
+        }
+        if let Some(s) = format_real_symbolic(im) {
+            return format!("{}i", s);
+        }
+        return format!("{:.4}i", im);
+    }
+
+    let re_str = format_real_symbolic(re).unwrap_or_else(|| format!("{:.4}", re));
+    let im_str = if approx_eq(im.abs(), 1.0) {
+        if im > 0.0 {
+            "+i".to_string()
+        } else {
+            "-i".to_string()
+        }
+    } else {
+        let im_sym = format_real_symbolic(im.abs());
+        let sign = if im > 0.0 { "+" } else { "-" };
+        match im_sym {
+            Some(s) => format!("{}{}i", sign, s.trim_start_matches('-')),
+            None => format!("{}{:.4}i", sign, im.abs()),
+        }
+    };
+
+    format!("{}{}", re_str, im_str)
+}
+
+pub fn format_probability(p: f64) -> String {
+    if approx_eq(p, 0.0) {
+        return "0".to_string();
+    }
+    if approx_eq(p, 1.0) {
+        return "1".to_string();
+    }
+    if approx_eq(p, 0.5) {
+        return "½".to_string();
+    }
+    if approx_eq(p, 0.25) {
+        return "¼".to_string();
+    }
+    if approx_eq(p, 0.75) {
+        return "¾".to_string();
+    }
+    if approx_eq(p, 0.125) {
+        return "⅛".to_string();
+    }
+    if approx_eq(p, 0.0625) {
+        return "¹⁄₁₆".to_string();
+    }
+    if approx_eq(p, 1.0 / 3.0) {
+        return "⅓".to_string();
+    }
+    if approx_eq(p, 2.0 / 3.0) {
+        return "⅔".to_string();
+    }
+
+    format!("{:.4}", p)
+}