From c87f802cf60b7ae5dfdca9ccfa011c5105d9947b Mon Sep 17 00:00:00 2001
From: Jett Chen <jettchen12345@gmail.com>
Date: Wed, 7 Jun 2023 20:44:07 +0800
Subject: [PATCH] add calc.exp, calc.ln (#1299)

Co-authored-by: Laurenz <laurmaedje@gmail.com>
---
 library/src/compute/calc.rs | 82 +++++++++++++++++++++++++++++++++++--
 tests/typ/compute/calc.typ  |  4 +-
 2 files changed, 81 insertions(+), 5 deletions(-)

diff --git a/library/src/compute/calc.rs b/library/src/compute/calc.rs
index 071cf164c..c1ae683e2 100644
--- a/library/src/compute/calc.rs
+++ b/library/src/compute/calc.rs
@@ -13,6 +13,7 @@ pub fn module() -> Module {
     let mut scope = Scope::new();
     scope.define("abs", abs_func());
     scope.define("pow", pow_func());
+    scope.define("exp", exp_func());
     scope.define("sqrt", sqrt_func());
     scope.define("sin", sin_func());
     scope.define("cos", cos_func());
@@ -25,6 +26,7 @@ pub fn module() -> Module {
     scope.define("cosh", cosh_func());
     scope.define("tanh", tanh_func());
     scope.define("log", log_func());
+    scope.define("ln", ln_func());
     scope.define("fact", fact_func());
     scope.define("perm", perm_func());
     scope.define("binom", binom_func());
@@ -96,7 +98,7 @@ cast! {
 pub fn pow(
     /// The base of the power.
     base: Num,
-    /// The exponent of the power. Must be non-negative.
+    /// The exponent of the power.
     exponent: Spanned<Num>,
     /// The callsite span.
     span: Span,
@@ -120,8 +122,15 @@ pub fn pow(
             .map(Num::Int)
             .ok_or("the result is too large")
             .at(span)?,
-        (a, Num::Int(b)) => Num::Float(a.float().powi(b as i32)),
-        (a, b) => Num::Float(a.float().powf(b.float())),
+        (a, b) => Num::Float(if a.float() == std::f64::consts::E {
+            b.float().exp()
+        } else if a.float() == 2.0 {
+            b.float().exp2()
+        } else if let Num::Int(b) = b {
+            a.float().powi(b as i32)
+        } else {
+            a.float().powf(b.float())
+        }),
     };
 
     if result.float().is_nan() {
@@ -131,6 +140,40 @@ pub fn pow(
     Ok(result)
 }
 
+/// Raise a value to some exponent of e.
+///
+/// ## Example { #example }
+/// ```example
+/// #calc.exp(3)
+/// ```
+///
+/// Display: Exponential
+/// Category: calculate
+#[func]
+pub fn exp(
+    /// The exponent of the power.
+    exponent: Spanned<Num>,
+    /// The callsite span.
+    span: Span,
+) -> SourceResult<f64> {
+    match exponent.v {
+        Num::Int(i) if i32::try_from(i).is_err() => {
+            bail!(exponent.span, "exponent is too large")
+        }
+        Num::Float(f) if !f.is_normal() && f != 0.0 => {
+            bail!(exponent.span, "exponent may not be infinite, subnormal, or NaN")
+        }
+        _ => {}
+    };
+
+    let result = exponent.v.float().exp();
+    if result.is_nan() {
+        bail!(span, "the result is not a real number")
+    }
+
+    Ok(result)
+}
+
 /// Calculate the square root of a number.
 ///
 /// ## Example { #example }
@@ -416,7 +459,9 @@ pub fn log(
         bail!(base.span, "base may not be zero, NaN, infinite, or subnormal")
     }
 
-    let result = if base.v == 2.0 {
+    let result = if base.v == std::f64::consts::E {
+        number.ln()
+    } else if base.v == 2.0 {
         number.log2()
     } else if base.v == 10.0 {
         number.log10()
@@ -431,6 +476,35 @@ pub fn log(
     Ok(result)
 }
 
+/// Calculate the natural logarithm of a number.
+///
+/// ## Example { #example }
+/// ```example
+/// #calc.ln(100)
+/// ```
+///
+/// Display: Natural Logarithm
+/// Category: calculate
+#[func]
+pub fn ln(
+    /// The number whose logarithm to calculate. Must be strictly positive.
+    value: Spanned<Num>,
+    /// The callsite span.
+    span: Span,
+) -> SourceResult<f64> {
+    let number = value.v.float();
+    if number <= 0.0 {
+        bail!(value.span, "value must be strictly positive")
+    }
+
+    let result = number.ln();
+    if result.is_infinite() {
+        bail!(span, "result close to -inf")
+    }
+
+    Ok(result)
+}
+
 /// Calculate the factorial of a number.
 ///
 /// ## Example { #example }
diff --git a/tests/typ/compute/calc.typ b/tests/typ/compute/calc.typ
index 3a1e85f32..cd97dfab3 100644
--- a/tests/typ/compute/calc.typ
+++ b/tests/typ/compute/calc.typ
@@ -94,9 +94,11 @@
 #test(calc.min("hi"), "hi")
 
 ---
-// Test the `calc` function.
+// Test the `pow`, `log`, `exp`, and `ln` functions.
 #test(calc.pow(10, 0), 1)
 #test(calc.pow(2, 4), 16)
+#test(calc.exp(2), calc.pow(calc.e, 2))
+#test(calc.ln(10), calc.log(10, base: calc.e))
 
 ---
 // Error: 10-16 zero to the power of zero is undefined