From 593a4f4666f0bc42790d6d033e64a2b38449090f Mon Sep 17 00:00:00 2001
From: Lorenzo Bodini <32436755+topongo@users.noreply.github.com>
Date: Tue, 14 Jan 2025 20:11:56 +0100
Subject: [PATCH] add `log` to expressions (#1271)

* feat: add `log` to expressions

* changelog: add `log`
---
 CHANGELOG.md                    | 1 +
 crates/simplexpr/src/eval.rs    | 8 ++++++++
 docs/src/expression_language.md | 1 +
 3 files changed, 10 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 123475c..96154b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ All notable changes to eww will be listed here, starting at changes since versio
 - Add `transform-origin-x`/`transform-origin-y` properties to transform widget (By: mario-kr)
 - Add keyboard support for button presses (By: julianschuler)
 - Support empty string for safe access operator (By: ModProg)
+- Add `log` function calls to simplexpr (By: topongo)
 
 ## [0.6.0] (21.04.2024)
 
diff --git a/crates/simplexpr/src/eval.rs b/crates/simplexpr/src/eval.rs
index d75c2c4..8ee0d84 100644
--- a/crates/simplexpr/src/eval.rs
+++ b/crates/simplexpr/src/eval.rs
@@ -500,6 +500,14 @@ fn call_expr_function(name: &str, args: Vec<DynVal>) -> Result<DynVal, EvalError
             })),
             _ => Err(EvalError::WrongArgCount(name.to_string())),
         },
+        "log" => match args.as_slice() {
+            [num, n] => {
+                let num = num.as_f64()?;
+                let n = n.as_f64()?;
+                Ok(DynVal::from(f64::log(num, n)))
+            }
+            _ => Err(EvalError::WrongArgCount(name.to_string())),
+        },
 
         _ => Err(EvalError::UnknownFunction(name.to_string())),
     }
diff --git a/docs/src/expression_language.md b/docs/src/expression_language.md
index 726ff79..106776a 100644
--- a/docs/src/expression_language.md
+++ b/docs/src/expression_language.md
@@ -44,6 +44,7 @@ Supported currently are the following features:
     - `sin(number)`, `cos(number)`, `tan(number)`, `cot(number)`: Calculate the trigonometric value of a given number in **radians**
     - `min(a, b)`, `max(a, b)`: Get the smaller or bigger number out of two given numbers
     - `powi(num, n)`, `powf(num, n)`: Raise number `num` to power `n`. `powi` expects `n` to be of type `i32`
+    - `log(num, n)`: Calculate the base `n` logarithm of `num`. `num`, `n` and return type are `f64`
     - `degtorad(number)`: Converts a number from degrees to radians
     - `radtodeg(number)`: Converts a number from radians to degrees
     - `replace(string, regex, replacement)`: Replace matches of a given regex in a string