diff --git a/build.zig b/build.zig
index 81a2adf..cbc5822 100644
--- a/build.zig
+++ b/build.zig
@@ -95,6 +95,7 @@ pub fn build(b: *std.Build) void {
         "src/01_lexic/number.zig",
         "src/01_lexic/identifier.zig",
         "src/01_lexic/datatype.zig",
+        "src/01_lexic/operator.zig",
         "src/01_lexic/token.zig",
         "src/01_lexic/utils.zig",
     };
diff --git a/src/01_lexic/identifier.zig b/src/01_lexic/identifier.zig
index 019eb37..18b1064 100644
--- a/src/01_lexic/identifier.zig
+++ b/src/01_lexic/identifier.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const assert = std.debug.assert;
 const token = @import("./token.zig");
 const utils = @import("./utils.zig");
 
@@ -11,10 +12,7 @@ const LexReturn = token.LexReturn;
 pub fn lex(input: []const u8, start: usize) LexError!?LexReturn {
     const cap = input.len;
     var final_pos = start;
-
-    if (start >= cap) {
-        return null;
-    }
+    assert(start < cap);
 
     // lex lowercase or underscore
     if (!utils.is_lowercase_underscore(input[start])) {
diff --git a/src/01_lexic/number.zig b/src/01_lexic/number.zig
index fc9dcf8..7ac1e90 100644
--- a/src/01_lexic/number.zig
+++ b/src/01_lexic/number.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const assert = std.debug.assert;
 const token = @import("./token.zig");
 const utils = @import("./utils.zig");
 
@@ -13,6 +14,7 @@ const is_decimal_digit = utils.is_decimal_digit;
 ///
 /// A number is either an Int or a Float.
 pub fn lex(input: []const u8, cap: usize, start: usize) LexError!?LexReturn {
+    assert(start < cap);
     const first_char = input[start];
 
     // Attempt to lex a hex, octal or binary number
@@ -74,6 +76,7 @@ fn prefixed(comptime prefix: u8, input: []const u8, cap: usize, start: usize) !?
 /// avoid confussion with PHP literal octals.
 /// Floating point numbers can.
 fn integer(input: []const u8, cap: usize, start: usize) LexError!?LexReturn {
+    assert(start < cap);
     const first_char = input[start];
     if (!is_decimal_digit(first_char)) {
         return null;
diff --git a/src/01_lexic/operator.zig b/src/01_lexic/operator.zig
new file mode 100644
index 0000000..bc53119
--- /dev/null
+++ b/src/01_lexic/operator.zig
@@ -0,0 +1,73 @@
+const std = @import("std");
+const assert = std.debug.assert;
+const token = @import("./token.zig");
+const utils = @import("./utils.zig");
+
+const Token = token.Token;
+const TokenType = token.TokenType;
+const LexError = token.LexError;
+const LexReturn = token.LexReturn;
+
+// lex an operator
+pub fn lex(input: []const u8, start: usize) LexError!?LexReturn {
+    const cap = input.len;
+    assert(start < cap);
+
+    // lex operator
+    if (utils.lex_many_1(utils.is_operator_char, input, start)) |final_pos| {
+        return .{
+            Token.init(input[start..final_pos], TokenType.Operator, start),
+            final_pos,
+        };
+    }
+    // no operator found
+    else {
+        return null;
+    }
+}
+
+test "should lex single operator" {
+    const input = "=";
+    const output = try lex(input, 0);
+
+    if (output) |tuple| {
+        const t = tuple[0];
+        try std.testing.expectEqualDeep("=", t.value);
+        try std.testing.expectEqual(1, tuple[1]);
+    } else {
+        try std.testing.expect(false);
+    }
+}
+
+test "should lex operator of len 2" {
+    const input = "+=";
+    const output = try lex(input, 0);
+
+    if (output) |tuple| {
+        const t = tuple[0];
+        try std.testing.expectEqualDeep("+=", t.value);
+        try std.testing.expectEqual(2, tuple[1]);
+    } else {
+        try std.testing.expect(false);
+    }
+}
+
+test "should lex operator of len 3" {
+    const input = " >>= ";
+    const output = try lex(input, 1);
+
+    if (output) |tuple| {
+        const t = tuple[0];
+        try std.testing.expectEqualDeep(">>=", t.value);
+        try std.testing.expectEqual(4, tuple[1]);
+    } else {
+        try std.testing.expect(false);
+    }
+}
+
+test "should not lex something else" {
+    const input = "322";
+    const output = try lex(input, 0);
+
+    try std.testing.expect(output == null);
+}
diff --git a/src/01_lexic/root.zig b/src/01_lexic/root.zig
index 5732ba2..a3f3fe1 100644
--- a/src/01_lexic/root.zig
+++ b/src/01_lexic/root.zig
@@ -1,8 +1,10 @@
 const std = @import("std");
+const assert = std.debug.assert;
 const number = @import("./number.zig");
 const identifier = @import("./identifier.zig");
 const datatype = @import("./datatype.zig");
 const token = @import("./token.zig");
+const operator = @import("./operator.zig");
 
 const TokenType = token.TokenType;
 const Token = token.Token;
@@ -16,9 +18,11 @@ pub fn tokenize(input: []const u8, alloc: std.mem.Allocator) !void {
 
     while (current_pos < input_len) {
         const actual_next_pos = ignore_whitespace(input, current_pos);
+        assert(current_pos <= actual_next_pos);
 
         // attempt to lex a number
         if (try number.lex(input, input_len, actual_next_pos)) |tuple| {
+            assert(tuple[1] > current_pos);
             const t = tuple[0];
             current_pos = tuple[1];
 
@@ -26,6 +30,7 @@ pub fn tokenize(input: []const u8, alloc: std.mem.Allocator) !void {
         }
         // attempt to lex an identifier
         else if (try identifier.lex(input, actual_next_pos)) |tuple| {
+            assert(tuple[1] > current_pos);
             const t = tuple[0];
             current_pos = tuple[1];
 
@@ -33,6 +38,15 @@ pub fn tokenize(input: []const u8, alloc: std.mem.Allocator) !void {
         }
         // attempt to lex a datatype
         else if (try datatype.lex(input, actual_next_pos)) |tuple| {
+            assert(tuple[1] > current_pos);
+            const t = tuple[0];
+            current_pos = tuple[1];
+
+            try tokens.append(t);
+        }
+        // attempt to lex an operator
+        else if (try operator.lex(input, actual_next_pos)) |tuple| {
+            assert(tuple[1] > current_pos);
             const t = tuple[0];
             current_pos = tuple[1];
 
diff --git a/src/01_lexic/token.zig b/src/01_lexic/token.zig
index 7e7f68c..18a8284 100644
--- a/src/01_lexic/token.zig
+++ b/src/01_lexic/token.zig
@@ -2,6 +2,7 @@ pub const TokenType = enum {
     Int,
     Float,
     Identifier,
+    Operator,
 };
 
 pub const Token = struct {
diff --git a/src/01_lexic/utils.zig b/src/01_lexic/utils.zig
index 98b2820..13bee33 100644
--- a/src/01_lexic/utils.zig
+++ b/src/01_lexic/utils.zig
@@ -35,6 +35,10 @@ pub fn is_identifier_char(c: u8) bool {
     return c == '_' or ('a' <= c and c <= 'z') or ('A' <= c and c <= 'Z') or ('0' <= c and c <= '9');
 }
 
+pub fn is_operator_char(c: u8) bool {
+    return c == '+' or c == '-' or c == '=' or c == '*' or c == '!' or c == '/' or c == '|' or c == '@' or c == '#' or c == '$' or c == '~' or c == '%' or c == '&' or c == '?' or c == '<' or c == '>' or c == '^' or c == '.' or c == ':';
+}
+
 /// Runs a discriminator function at least once,
 /// and returns the end position of the lex.
 ///
@@ -44,7 +48,7 @@ pub fn lex_many_1(
     comptime lex_fun: fn (c: u8) bool,
     input: []const u8,
     start: usize,
-) usize {
+) ?usize {
     // assert that there is input left
     const cap = input.len;
     var current_pos = start;