From d179552b3ca521cd7bc91d000218bd65bef814b7 Mon Sep 17 00:00:00 2001
From: stefan-gorules <127550877+stefan-gorules@users.noreply.github.com>
Date: Wed, 14 May 2025 08:21:29 +0200
Subject: [PATCH] feat: trunc function and decimal places for round (optional)
 (#349)

---
 core/expression/src/functions/internal.rs | 47 +++++++++++++++++++++--
 core/expression/src/parser/unary.rs       |  1 +
 core/expression/tests/data/standard.csv   | 35 ++++++++++++++++-
 3 files changed, 79 insertions(+), 4 deletions(-)

diff --git a/core/expression/src/functions/internal.rs b/core/expression/src/functions/internal.rs
index 3763fe20..abce92ad 100644
--- a/core/expression/src/functions/internal.rs
+++ b/core/expression/src/functions/internal.rs
@@ -35,6 +35,7 @@ pub enum InternalFunction {
     Floor,
     Ceil,
     Round,
+    Trunc,
 
     // Type
     IsNumeric,
@@ -173,9 +174,32 @@ impl From<&InternalFunction> for Rc<dyn FunctionDefinition> {
                 signature: FunctionSignature::single(VT::Number, VT::Number),
             }),
 
-            IF::Round => Rc::new(StaticFunction {
+            IF::Round => Rc::new(CompositeFunction {
                 implementation: Rc::new(imp::round),
-                signature: FunctionSignature::single(VT::Number, VT::Number),
+                signatures: vec![
+                    FunctionSignature {
+                        parameters: vec![VT::Number],
+                        return_type: VT::Number,
+                    },
+                    FunctionSignature {
+                        parameters: vec![VT::Number, VT::Number],
+                        return_type: VT::Number,
+                    },
+                ],
+            }),
+
+            IF::Trunc => Rc::new(CompositeFunction {
+                implementation: Rc::new(imp::trunc),
+                signatures: vec![
+                    FunctionSignature {
+                        parameters: vec![VT::Number],
+                        return_type: VT::Number,
+                    },
+                    FunctionSignature {
+                        parameters: vec![VT::Number, VT::Number],
+                        return_type: VT::Number,
+                    },
+                ],
             }),
 
             IF::Sum => Rc::new(StaticFunction {
@@ -404,7 +428,24 @@ pub(crate) mod imp {
 
     pub fn round(args: Arguments) -> anyhow::Result<V> {
         let a = args.number(0)?;
-        Ok(V::Number(a.round()))
+        let dp = args
+            .onumber(1)?
+            .map(|v| v.to_u32().context("Invalid number of decimal places"))
+            .transpose()?
+            .unwrap_or(0);
+
+        Ok(V::Number(a.round_dp(dp)))
+    }
+
+    pub fn trunc(args: Arguments) -> anyhow::Result<V> {
+        let a = args.number(0)?;
+        let dp = args
+            .onumber(1)?
+            .map(|v| v.to_u32().context("Invalid number of decimal places"))
+            .transpose()?
+            .unwrap_or(0);
+
+        Ok(V::Number(a.trunc_with_scale(dp)))
     }
 
     pub fn rand(args: Arguments) -> anyhow::Result<V> {
diff --git a/core/expression/src/parser/unary.rs b/core/expression/src/parser/unary.rs
index 0658e725..db3eba4f 100644
--- a/core/expression/src/parser/unary.rs
+++ b/core/expression/src/parser/unary.rs
@@ -353,6 +353,7 @@ impl From<&Node<'_>> for UnaryNodeBehaviour {
                     InternalFunction::Floor => CompareWithReference(Equal),
                     InternalFunction::Ceil => CompareWithReference(Equal),
                     InternalFunction::Round => CompareWithReference(Equal),
+                    InternalFunction::Trunc => CompareWithReference(Equal),
                     InternalFunction::String => CompareWithReference(Equal),
                     InternalFunction::Number => CompareWithReference(Equal),
                     InternalFunction::Bool => CompareWithReference(Equal),
diff --git a/core/expression/tests/data/standard.csv b/core/expression/tests/data/standard.csv
index 24c63573..dd6d087e 100644
--- a/core/expression/tests/data/standard.csv
+++ b/core/expression/tests/data/standard.csv
@@ -432,4 +432,37 @@ x not in [1..10];{"x":5};false
 
 # Interval iterator
 map([0..5], # * 2);;[0, 2, 4, 6, 8, 10]
-filter([0..10], # % 2 == 0);;[0, 2, 4, 6, 8, 10]
\ No newline at end of file
+filter([0..10], # % 2 == 0);;[0, 2, 4, 6, 8, 10]
+
+# Rounding
+round(7.4);; 7
+round(7.5);; 8
+round(7.6);; 8
+round(-7.4);; -7
+round(-7.5);; -8
+round(-7.6);; -8
+
+round(7.444, 0);; 7
+round(7.444, 1);; 7.4
+round(7.444, 2);; 7.44
+round(7.555, 0);; 8
+round(7.555, 1);; 7.6
+round(7.555, 2);; 7.56
+round(-7.444, 2);; -7.44
+round(-7.555, 2);; -7.56
+
+trunc(7.4);; 7
+trunc(7.5);; 7
+trunc(7.6);; 7
+trunc(-7.4);; -7
+trunc(-7.5);; -7
+trunc(-7.6);; -7
+
+trunc(7.444, 0);; 7
+trunc(7.444, 1);; 7.4
+trunc(7.444, 2);; 7.44
+trunc(7.999, 0);; 7
+trunc(7.999, 1);; 7.9
+trunc(7.999, 2);; 7.99
+trunc(-7.444, 2);; -7.44
+trunc(-7.999, 2);; -7.99
\ No newline at end of file