From ce70796581474326097ab28f049f4e53a2d2f166 Mon Sep 17 00:00:00 2001
From: simon brahan <tntpiranha@gmail.com>
Date: Mon, 7 Oct 2019 23:40:08 +0100
Subject: [PATCH] Implement exponentiation operator (#130)

* Exponentiation (**) now works.

Added missing NumOp type, token match, and calculation.

* Assignment exponentiation (**=) now works.

Added missing AssignOp type, token match, and calculation.

This fixes #89.
---
 src/lib/exec.rs          |  2 ++
 src/lib/js/value.rs      |  4 ++++
 src/lib/syntax/ast/op.rs |  7 +++++++
 src/lib/syntax/parser.rs | 30 ++++++++++++++++++++++++++++++
 4 files changed, 43 insertions(+)

diff --git a/src/lib/exec.rs b/src/lib/exec.rs
index ceb7d9e07e..fd1382cc38 100644
--- a/src/lib/exec.rs
+++ b/src/lib/exec.rs
@@ -39,6 +39,7 @@ fn exec_assign_op(op: &AssignOp, v_a: ValueData, v_b: ValueData) -> Value {
         AssignOp::Add => v_a + v_b,
         AssignOp::Sub => v_a - v_b,
         AssignOp::Mul => v_a * v_b,
+        AssignOp::Pow => v_a.as_num_to_power(v_b),
         AssignOp::Div => v_a / v_b,
         AssignOp::Mod => v_a % v_b,
         AssignOp::And => v_a & v_b,
@@ -227,6 +228,7 @@ impl Executor for Interpreter {
                     NumOp::Add => v_a + v_b,
                     NumOp::Sub => v_a - v_b,
                     NumOp::Mul => v_a * v_b,
+                    NumOp::Pow => v_a.as_num_to_power(v_b),
                     NumOp::Div => v_a / v_b,
                     NumOp::Mod => v_a % v_b,
                 }))
diff --git a/src/lib/js/value.rs b/src/lib/js/value.rs
index a0bd699035..53a7d4bdec 100644
--- a/src/lib/js/value.rs
+++ b/src/lib/js/value.rs
@@ -551,6 +551,10 @@ impl ValueData {
             }
         }
     }
+
+    pub fn as_num_to_power(&self, other: ValueData) -> ValueData {
+        ValueData::Number(self.to_num().powf(other.to_num()))
+    }
 }
 
 impl Default for ValueData {
diff --git a/src/lib/syntax/ast/op.rs b/src/lib/syntax/ast/op.rs
index e71ec44917..83a2858670 100644
--- a/src/lib/syntax/ast/op.rs
+++ b/src/lib/syntax/ast/op.rs
@@ -24,6 +24,8 @@ pub enum NumOp {
     Div,
     /// `a * b` - Multiplication
     Mul,
+    /// `a ** b` - Exponentiation
+    Pow,
     /// `a % b` - Modulus
     Mod,
 }
@@ -38,6 +40,7 @@ impl Display for NumOp {
                 NumOp::Sub => "-",
                 NumOp::Div => "/",
                 NumOp::Mul => "*",
+                NumOp::Pow => "**",
                 NumOp::Mod => "%",
             }
         )
@@ -193,6 +196,7 @@ impl Operator for BinOp {
     }
     fn get_precedence(&self) -> u64 {
         match *self {
+            BinOp::Num(NumOp::Pow) => 4,
             BinOp::Num(NumOp::Mul) | BinOp::Num(NumOp::Div) | BinOp::Num(NumOp::Mod) => 5,
             BinOp::Num(NumOp::Add) | BinOp::Num(NumOp::Sub) => 6,
             BinOp::Bit(BitOp::Shl) | BinOp::Bit(BitOp::Shr) => 7,
@@ -239,6 +243,8 @@ pub enum AssignOp {
     Sub,
     /// `a *= b` - Mul assign
     Mul,
+    /// `a **= b` - Exponent assign
+    Pow,
     /// `a /= b` - Div assign
     Div,
     /// `a %= b` - Modulus assign
@@ -264,6 +270,7 @@ impl Display for AssignOp {
                 AssignOp::Add => "+=",
                 AssignOp::Sub => "-=",
                 AssignOp::Mul => "*=",
+                AssignOp::Pow => "**=",
                 AssignOp::Div => "/=",
                 AssignOp::Mod => "%=",
                 AssignOp::And => "&=",
diff --git a/src/lib/syntax/parser.rs b/src/lib/syntax/parser.rs
index 50d5b11b04..4c94e523c6 100644
--- a/src/lib/syntax/parser.rs
+++ b/src/lib/syntax/parser.rs
@@ -671,6 +671,9 @@ impl Parser {
             TokenData::Punctuator(Punctuator::AssignMul) => {
                 result = self.binop(BinOp::Assign(AssignOp::Mul), expr)?
             }
+            TokenData::Punctuator(Punctuator::AssignPow) => {
+                result = self.binop(BinOp::Assign(AssignOp::Pow), expr)?
+            }
             TokenData::Punctuator(Punctuator::AssignDiv) => {
                 result = self.binop(BinOp::Assign(AssignOp::Div), expr)?
             }
@@ -711,6 +714,9 @@ impl Parser {
             TokenData::Punctuator(Punctuator::Mul) => {
                 result = self.binop(BinOp::Num(NumOp::Mul), expr)?
             }
+            TokenData::Punctuator(Punctuator::Pow) => {
+                result = self.binop(BinOp::Num(NumOp::Pow), expr)?
+            }
             TokenData::Punctuator(Punctuator::Div) => {
                 result = self.binop(BinOp::Num(NumOp::Div), expr)?
             }
@@ -1148,6 +1154,22 @@ mod tests {
                 Expr::new(ExprDef::Const(Const::Num(2.0))),
             )],
         );
+        check_parser(
+            "a ** b",
+            &[create_bin_op(
+                BinOp::Num(NumOp::Pow),
+                Expr::new(ExprDef::Local(String::from("a"))),
+                Expr::new(ExprDef::Local(String::from("b"))),
+            )],
+        );
+        check_parser(
+            "a**2",
+            &[create_bin_op(
+                BinOp::Num(NumOp::Pow),
+                Expr::new(ExprDef::Local(String::from("a"))),
+                Expr::new(ExprDef::Const(Const::Num(2.0))),
+            )],
+        );
         check_parser(
             "a % b",
             &[create_bin_op(
@@ -1299,6 +1321,14 @@ mod tests {
                 Expr::new(ExprDef::Local(String::from("b"))),
             )],
         );
+        check_parser(
+            "a **= b",
+            &[create_bin_op(
+                BinOp::Assign(AssignOp::Pow),
+                Expr::new(ExprDef::Local(String::from("a"))),
+                Expr::new(ExprDef::Local(String::from("b"))),
+            )],
+        );
         check_parser(
             "a /= b",
             &[create_bin_op(