4 files changed, 57 insertions, 1 deletions

diff --git a/src/Lexer.zig b/src/Lexer.zig
index f59737e..c938116 100644
--- a/src/Lexer.zig
+++ b/src/Lexer.zig
@@ -21,6 +21,7 @@ pub const Token = struct {
         let,
         @"if",
         @"else",
+        @"while",
     };
 };
 
@@ -122,7 +123,7 @@ fn identifierOrKeyword(self: *Self) Token {
         }
         const value = self.source[self.start..self.pos];
         return self.create(switch (std.meta.stringToEnum(Token.Type, value) orelse .invalid) {
-            .let, .@"if", .@"else" => |t| t,
+            .let, .@"if", .@"else", .@"while" => |t| t,
             else => .identifier,
         });
     }
diff --git a/src/compile.zig b/src/compile.zig
index c0ba77d..4d39293 100644
--- a/src/compile.zig
+++ b/src/compile.zig
@@ -336,6 +336,34 @@ const CompileContext = struct {
                 const val = try self.compileExpr(assign_var.value);
                 try self.assignLocalVar(local, val);
             },
+            .@"while" => |@"while"| {
+                const curr = self.current_block;
+                const cond_block = try self.switchToNewBlock();
+                self.current_block = curr;
+                try self.addInstr(.{
+                    .loc = stmt.loc,
+                    .type = .{ .jump = .{ .to = cond_block } },
+                });
+                const do = try self.switchToNewBlock();
+                const after = try self.switchToNewBlock();
+                self.current_block = cond_block;
+                const cond = try self.compileExpr(@"while".cond);
+                try self.addInstr(.{
+                    .loc = stmt.loc,
+                    .type = .{ .branch = .{
+                        .cond = cond,
+                        .true = .{ .to = do },
+                        .false = .{ .to = after },
+                    } },
+                });
+                self.current_block = do;
+                try self.compileBlock(@"while".do);
+                try self.addInstr(.{
+                    .loc = stmt.loc,
+                    .type = .{ .jump = .{ .to = cond_block } },
+                });
+                self.current_block = after;
+            },
         }
     }
 
diff --git a/src/main.zig b/src/main.zig
index 314459b..becbf97 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -37,6 +37,11 @@ pub fn main() !void {
     const source =
         \\{
         \\    let x = 10
+        \\    let y = 5
+        \\    while y {
+        \\        x = x + x
+        \\        y = y - 1
+        \\    }
         \\    if x {
         \\        # let x = read_int(0)
         \\        # print(18446744073709551615)
diff --git a/src/parse.zig b/src/parse.zig
index 8347687..e675fbe 100644
--- a/src/parse.zig
+++ b/src/parse.zig
@@ -45,12 +45,18 @@ pub const Stmt = struct {
         expr: *const Expr,
         assign_var: AssignVar,
         block: Block,
+        @"while": While,
 
         pub const AssignVar = struct {
             ident: Lexer.Location,
             is_decl: bool,
             value: *const Expr,
         };
+
+        pub const While = struct {
+            cond: *const Expr,
+            do: Block,
+        };
     };
 
     fn format(self: Stmt, writer: anytype, source: []const u8, indent: usize) !void {
@@ -63,6 +69,10 @@ pub const Stmt = struct {
                 assign_var.ident.getIdent(source),
                 fmt(assign_var.value, source, indent),
             }),
+            .@"while" => |@"while"| try writer.print("while {} {}", .{
+                fmt(@"while".cond, source, indent),
+                fmt(@"while".do, source, indent),
+            }),
         };
     }
 };
@@ -165,6 +175,18 @@ pub fn statement(allocator: Allocator, lexer: *Lexer) ParseError!Stmt {
                 .type = .{ .block = b },
             };
         },
+        .@"while" => {
+            const @"while" = lexer.next();
+            const cond = try expression(allocator, lexer);
+            const do = try block(allocator, lexer);
+            return .{
+                .loc = @"while".loc.combine(do.loc),
+                .type = .{ .@"while" = .{
+                    .cond = cond,
+                    .do = do,
+                } },
+            };
+        },
         else => {
             const lhs = try expression(allocator, lexer);
             if (lexer.peek().type == .equal) {