symbolic: init

src/function_manager.rs

@@ -46,7 +46,7 @@ fn button_area_button<'a>(text: impl Into<WidgetText>) -> Button<'a> {
 impl FunctionManager {
     pub fn new() -> Self {
         Self {
-            functions: Vec::new()
+            functions: Vec::new(),
         }
     }
 

src/lib.rs

@@ -6,6 +6,7 @@ mod function_entry;
 mod function_manager;
 mod math_app;
 mod misc;
+pub mod symbolic;
 mod unicode_helper;
 mod widgets;
 

src/misc.rs

@@ -150,20 +150,6 @@ pub fn step_helper(max_i: usize, min_x: f64, step: f64) -> Vec<f64> {
         .collect()
 }
 
-// TODO: use in hovering over points
-/// Attempts to see what variable `x` is almost
-#[allow(dead_code)]
-pub fn almost_variable(x: f64) -> Option<char> {
-    const EPSILON: f32 = f32::EPSILON * 2.0;
-    if emath::almost_equal(x as f32, std::f32::consts::E, EPSILON) {
-        Some('e')
-    } else if emath::almost_equal(x as f32, std::f32::consts::PI, EPSILON) {
-        Some('π')
-    } else {
-        None
-    }
-}
-
 pub const HASH_LENGTH: usize = 8;
 
 /// Represents bytes used to represent hash info

src/symbolic.rs

@@ -0,0 +1,210 @@
+use std::fmt;
+
+/// Maximum denominator to consider when checking for rational approximations.
+const MAX_DENOMINATOR: i64 = 12;
+
+/// Maximum coefficient to consider for multiples of special constants.
+const MAX_COEFFICIENT: i64 = 12;
+
+/// Represents a symbolic mathematical value.
+#[derive(Debug, Clone, PartialEq)]
+pub struct SymbolicValue {
+    /// The original numeric value
+    value: f64,
+    /// The symbolic representation
+    repr: SymbolicRepr,
+}
+
+/// The type of symbolic representation.
+#[derive(Debug, Clone, PartialEq)]
+enum SymbolicRepr {
+    /// An integer value
+    Integer(i64),
+    /// A simple fraction: numerator / denominator
+    Fraction { numerator: i64, denominator: i64 },
+    /// A multiple of a constant: (numerator / denominator) * constant
+    ConstantMultiple {
+        numerator: i64,
+        denominator: i64,
+        constant: Constant,
+    },
+}
+
+/// Known mathematical constants.
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum Constant {
+    Pi,
+    E,
+    Sqrt(i64),
+}
+
+impl Constant {
+    fn value(self) -> f64 {
+        match self {
+            Constant::Pi => std::f64::consts::PI,
+            Constant::E => std::f64::consts::E,
+            Constant::Sqrt(n) => (n as f64).sqrt(),
+        }
+    }
+
+    fn name(self) -> String {
+        match self {
+            Constant::Pi => "pi".to_string(),
+            Constant::E => "e".to_string(),
+            Constant::Sqrt(n) => format!("sqrt({})", n),
+        }
+    }
+}
+
+/// All constants to try, in order of priority.
+const CONSTANTS: &[Constant] = &[
+    Constant::Pi,
+    Constant::E,
+    Constant::Sqrt(2),
+    Constant::Sqrt(3),
+    Constant::Sqrt(5),
+    Constant::Sqrt(6),
+    Constant::Sqrt(7),
+];
+
+impl SymbolicValue {
+    /// Returns the original numeric value.
+    pub fn numeric_value(&self) -> f64 {
+        self.value
+    }
+}
+
+impl fmt::Display for SymbolicValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match &self.repr {
+            SymbolicRepr::Integer(n) => write!(f, "{}", n),
+            SymbolicRepr::Fraction {
+                numerator,
+                denominator,
+            } => write!(f, "{}/{}", numerator, denominator),
+            SymbolicRepr::ConstantMultiple {
+                numerator,
+                denominator,
+                constant,
+            } => format_constant_multiple(f, *numerator, *denominator, &constant.name()),
+        }
+    }
+}
+
+/// Helper function to format a constant multiple like "2pi/3" or "-pi/2"
+fn format_constant_multiple(
+    f: &mut fmt::Formatter<'_>,
+    numerator: i64,
+    denominator: i64,
+    constant: &str,
+) -> fmt::Result {
+    let sign = if numerator < 0 { "-" } else { "" };
+    let abs_num = numerator.abs();
+
+    match (abs_num, denominator) {
+        (1, 1) => write!(f, "{}{}", sign, constant),
+        (_, 1) => write!(f, "{}{}{}", sign, abs_num, constant),
+        (1, _) => write!(f, "{}{}/{}", sign, constant, denominator),
+        (_, _) => write!(f, "{}{}{}/{}", sign, abs_num, constant, denominator),
+    }
+}
+
+/// Attempts to find a symbolic representation for the given numeric value.
+///
+/// Returns `Some(SymbolicValue)` if the value can be represented symbolically,
+/// or `None` if no suitable symbolic representation is found.
+///
+/// # Examples
+///
+/// ```
+/// use ytbn_graphing_software::symbolic::try_symbolic;
+/// use std::f64::consts::PI;
+///
+/// let sym = try_symbolic(PI).unwrap();
+/// assert_eq!(sym.to_string(), "pi");
+///
+/// let sym = try_symbolic(PI / 2.0).unwrap();
+/// assert_eq!(sym.to_string(), "pi/2");
+/// ```
+pub fn try_symbolic(x: f64) -> Option<SymbolicValue> {
+    if !x.is_finite() {
+        return None;
+    }
+
+    // Check for zero
+    if x.abs() < f64::EPSILON {
+        return Some(SymbolicValue {
+            value: x,
+            repr: SymbolicRepr::Integer(0),
+        });
+    }
+
+    // Try each constant in order of preference
+    for &constant in CONSTANTS {
+        if let Some(repr) = try_constant_multiple(x, constant) {
+            return Some(SymbolicValue { value: x, repr });
+        }
+    }
+
+    // Fall back to rational approximation
+    try_rational(x).map(|repr| SymbolicValue { value: x, repr })
+}
+
+/// Try to represent x as (numerator/denominator) * constant
+fn try_constant_multiple(x: f64, constant: Constant) -> Option<SymbolicRepr> {
+    let c = constant.value();
+
+    for denom in 1..=MAX_DENOMINATOR {
+        let num_f = x * (denom as f64) / c;
+        let num = num_f.round() as i64;
+
+        // Skip if coefficient is zero or too large
+        if num == 0 || num.abs() > MAX_COEFFICIENT * denom {
+            continue;
+        }
+
+        let expected = (num as f64) * c / (denom as f64);
+        if (x - expected).abs() < f64::EPSILON {
+            let g = gcd(num.abs(), denom);
+            return Some(SymbolicRepr::ConstantMultiple {
+                numerator: num / g,
+                denominator: denom / g,
+                constant,
+            });
+        }
+    }
+
+    None
+}
+
+/// Try to represent x as a simple fraction: numerator/denominator
+fn try_rational(x: f64) -> Option<SymbolicRepr> {
+    for denom in 1..=MAX_DENOMINATOR {
+        let num_f = x * (denom as f64);
+        let num = num_f.round() as i64;
+
+        if (x - (num as f64) / (denom as f64)).abs() < f64::EPSILON {
+            let g = gcd(num.abs(), denom);
+            let (num, denom) = (num / g, denom / g);
+
+            return Some(if denom == 1 {
+                SymbolicRepr::Integer(num)
+            } else {
+                SymbolicRepr::Fraction {
+                    numerator: num,
+                    denominator: denom,
+                }
+            });
+        }
+    }
+
+    None
+}
+
+/// Compute the greatest common divisor using Euclidean algorithm.
+fn gcd(mut a: i64, mut b: i64) -> i64 {
+    while b != 0 {
+        (a, b) = (b, a % b);
+    }
+    a
+}