feat: assignment operators (#10)

* feat: assignment operators

* docs: use assignment operators

Co-authored-by: Garrit Franke <garrit@slashdev.space>

docs/concepts/control-flow.md

@@ -113,7 +113,7 @@ fn main() {
     while index < 5 {
         println("the value is: " + a[index])
 
-        index = index + 1
+        index += 1
     }
 }
 ```

examples/bubblesort.sb

@@ -14,10 +14,10 @@ fn main() {
                 arr[d+1] = swap
             }
 
-            d = d + 1
+            d += 1
         }
 
-        c = c + 1
+        c += 1
     }
 
     println(arr)

lib/stdio.sb

@@ -13,7 +13,7 @@ fn println(msg: string) {
 fn len(arr: int[]): int {
     let c: int = 0
     while arr[c] {
-        c = c + 1
+        c += 1
     }
 
     return c

src/generator/js.rs

@@ -242,6 +242,10 @@ fn generate_bin_op(left: Expression, op: BinOp, right: Expression) -> String {
         BinOp::NotEqual => "!==",
         BinOp::Or => "||",
         BinOp::Subtraction => "-",
+        BinOp::AddAssign => "+=",
+        BinOp::SubtractAssign => "-=",
+        BinOp::MultiplyAssign => "*=",
+        BinOp::DivideAssign => "/=",
     };
     format!(
         "({l} {op} {r})",

src/lexer/mod.rs

@@ -94,6 +94,14 @@ pub enum TokenKind {
     And,
     /// "||"
     Or,
+    /// "+="
+    PlusEqual,
+    /// "-="
+    MinusEqual,
+    /// "*="
+    StarEqual,
+    /// "/="
+    SlashEqual,
     /// "("
     BraceOpen,
     /// ")"
@@ -193,15 +201,37 @@ impl Cursor<'_> {
             c if is_whitespace(c) => self.whitespace(),
             '0'..='9' => self.number(),
             '"' | '\'' => self.string(),
-            '+' => Plus,
-            '-' => Minus,
-            '*' => Star,
+            '+' => match self.first() {
+                '=' => {
+                    self.bump();
+                    PlusEqual
+                }
+                _ => Plus,
+            },
+            '-' => match self.first() {
+                '=' => {
+                    self.bump();
+                    MinusEqual
+                }
+                _ => Minus,
+            },
+            '*' => match self.first() {
+                '=' => {
+                    self.bump();
+                    StarEqual
+                }
+                _ => Star,
+            },
             '%' => Percent,
             '/' => match self.first() {
                 '/' => {
                     self.bump();
                     self.comment()
                 }
+                '=' => {
+                    self.bump();
+                    SlashEqual
+                }
                 _ => Slash,
             },
             '=' => match self.first() {

src/parser/node_type.rs

@@ -146,6 +146,10 @@ pub enum BinOp {
     NotEqual,
     And,
     Or,
+    AddAssign,
+    SubtractAssign,
+    MultiplyAssign,
+    DivideAssign,
 }
 
 impl TryFrom<TokenKind> for BinOp {
@@ -165,6 +169,10 @@ impl TryFrom<TokenKind> for BinOp {
             TokenKind::NotEqual => Ok(BinOp::NotEqual),
             TokenKind::And => Ok(BinOp::And),
             TokenKind::Or => Ok(BinOp::Or),
+            TokenKind::PlusEqual => Ok(BinOp::AddAssign),
+            TokenKind::MinusEqual => Ok(BinOp::SubtractAssign),
+            TokenKind::StarEqual => Ok(BinOp::MultiplyAssign),
+            TokenKind::SlashEqual => Ok(BinOp::DivideAssign),
             other => Err(format!("Token {:?} cannot be converted into a BinOp", other).into()),
         }
     }

src/parser/rules.rs

@@ -152,6 +152,10 @@ impl Parser {
                         TokenKind::Assign => self.parse_assignent(Some(expr)),
                         _ => Ok(Statement::Exp(expr)),
                     }
+                } else if let Ok(_) = BinOp::try_from(self.peek()?.kind) {
+                    let expr = Expression::Variable(ident.into());
+                    let state = Statement::Exp(self.parse_bin_op(Some(expr))?);
+                    Ok(state)
                 } else {
                     let state = Statement::Exp(Expression::Variable(ident.into()));
                     Ok(state)

src/parser/tests.rs

@@ -463,7 +463,7 @@ fn test_array_access_in_loop() {
     
         while i < 5 {
           println(x[i])
-          i = i + 1
+          i += 1
         }
     }
     ";

tests/operator_assignments.sb

@@ -0,0 +1,8 @@
+fn main() {
+    let x = 10
+    x += 1
+    x -= 2
+    x *= 2
+    x /= 2
+    println(x)
+}