From d35ecc0caf2d6ba54b5934f606796687303275b0 Mon Sep 17 00:00:00 2001
From: Vincent Ambo <mail@tazj.in>
Date: Mon, 8 Aug 2022 02:16:28 +0300
Subject: feat(tvix/eval): implement simple arithmetic binary operations

Implements simple arithmetic operations (+, -, *, /).

There is some scaffolding included to pop and coerce pairs of numbers,
as the Nix language will let arithmetic operators apply to arbitrary
pairs of number types (always resulting in floats if the types are
mixed).

Change-Id: I5f62c363bdea8baa6ef812cc64c5406759d257cf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6074
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
---
 tvix/eval/src/vm.rs | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

(limited to 'tvix/eval/src/vm.rs')

diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs
index e35cd99b1e3d..077acfcc1b8d 100644
--- a/tvix/eval/src/vm.rs
+++ b/tvix/eval/src/vm.rs
@@ -1,7 +1,12 @@
 //! This module implements the virtual (or abstract) machine that runs
 //! Tvix bytecode.
 
-use crate::{chunk::Chunk, errors::EvalResult, opcode::OpCode, value::Value};
+use crate::{
+    chunk::Chunk,
+    errors::{Error, EvalResult},
+    opcode::OpCode,
+    value::{NumberPair, Value},
+};
 
 pub struct VM {
     ip: usize,
@@ -18,6 +23,30 @@ impl VM {
         self.stack.pop().expect("TODO")
     }
 
+    fn pop_number_pair(&mut self) -> EvalResult<NumberPair> {
+        let v2 = self.pop();
+        let v1 = self.pop();
+
+        match (v1, v2) {
+            (Value::Integer(i1), Value::Integer(i2)) => Ok(NumberPair::Integer(i1, i2)),
+
+            (Value::Float(f1), Value::Float(f2)) => Ok(NumberPair::Floats(f1, f2)),
+
+            (Value::Integer(i1), Value::Float(f2)) => Ok(NumberPair::Floats(i1 as f64, f2)),
+
+            (Value::Float(f1), Value::Integer(i2)) => Ok(NumberPair::Floats(f1, i2 as f64)),
+
+            _ => Err(Error::TypeError {
+                expected: "number (either int or float)",
+                actual: if v1.is_number() {
+                    v2.type_of()
+                } else {
+                    v1.type_of()
+                },
+            }),
+        }
+    }
+
     fn inc_ip(&mut self) -> OpCode {
         let op = self.chunk.code[self.ip];
         self.ip += 1;
@@ -32,6 +61,26 @@ impl VM {
                     self.push(c);
                 }
 
+                OpCode::OpAdd => match self.pop_number_pair()? {
+                    NumberPair::Floats(f1, f2) => self.push(Value::Float(f1 + f2)),
+                    NumberPair::Integer(i1, i2) => self.push(Value::Integer(i1 + i2)),
+                },
+
+                OpCode::OpSub => match self.pop_number_pair()? {
+                    NumberPair::Floats(f1, f2) => self.push(Value::Float(f1 - f2)),
+                    NumberPair::Integer(i1, i2) => self.push(Value::Integer(i1 - i2)),
+                },
+
+                OpCode::OpMul => match self.pop_number_pair()? {
+                    NumberPair::Floats(f1, f2) => self.push(Value::Float(f1 * f2)),
+                    NumberPair::Integer(i1, i2) => self.push(Value::Integer(i1 * i2)),
+                },
+
+                OpCode::OpDiv => match self.pop_number_pair()? {
+                    NumberPair::Floats(f1, f2) => self.push(Value::Float(f1 / f2)),
+                    NumberPair::Integer(i1, i2) => self.push(Value::Integer(i1 / i2)),
+                },
+
                 OpCode::OpNull => todo!(),
                 OpCode::OpTrue => todo!(),
                 OpCode::OpFalse => todo!(),
-- 
cgit 1.4.1