From 4484d1b2c16b9d57a5376a74d97e8fac2e995940 Mon Sep 17 00:00:00 2001
From: m93a <m93a.cz@gmail.com>
Date: Sat, 18 Sep 2021 08:21:07 +0200
Subject: [PATCH] add log2 & log10, document exists & empty

---
 README.md       | 4 ++++
 src/filtrex.mjs | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/README.md b/README.md
index 792995c..3f5c330 100644
--- a/README.md
+++ b/README.md
@@ -120,8 +120,12 @@ Built-in functions | Description
 --- | ---
 abs(x) | Absolute value
 ceil(x) | Round floating point up
+empty(x) | True if _x_ is `undefined`, `null`, an empty array or an empty string
+exists(x) | True unless _x_ is `undefined` or `null`
 floor(x) | Round floating point down
 log(x) | Natural logarithm
+log2(x) | Logarithm base two
+log10(x) | Logarithm base ten
 max(a, b, c...) | Max value (variable length of args)
 min(a, b, c...) | Min value (variable length of args)
 round(x) | Round floating point
diff --git a/src/filtrex.mjs b/src/filtrex.mjs
index 63c59da..c24ab6a 100644
--- a/src/filtrex.mjs
+++ b/src/filtrex.mjs
@@ -115,6 +115,8 @@ export function compileExpression(expression, options) {
         ceil: Math.ceil,
         floor: Math.floor,
         log: Math.log,
+        log2: Math.log2,
+        log10: Math.log10,
         max: Math.max,
         min: Math.min,
         round: Math.round,