diff --git a/CHANGELOG.md b/CHANGELOG.md
index 72c62ca..0b3adbc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@
 - [x] Scan octal and binary numbers
 - [x] Simple type checking
 - [x] Check for conflicting identifiers at the current scope
+- [x] Semantic check for unary operator
 
 
 ## v0.1.0
diff --git a/src/codegen/php/expression/primary_expression.rs b/src/codegen/php/expression/primary_expression.rs
index a071d14..b728fb1 100644
--- a/src/codegen/php/expression/primary_expression.rs
+++ b/src/codegen/php/expression/primary_expression.rs
@@ -8,6 +8,13 @@ impl Transpilable for PPrimary<'_> {
             PPrimary::StringLiteral(value) => format!("\"{}\"", value),
             PPrimary::Variable(name) => format!("${}", name),
             PPrimary::Symbol(name) => format!("{}", name),
+            PPrimary::BoolLiteral(bool) => {
+                if *bool {
+                    String::from("true")
+                } else {
+                    String::from("false")
+                }
+            }
         }
     }
 }
diff --git a/src/codegen/php/statement_list.rs b/src/codegen/php/statement_list.rs
index 0af1b8c..7455654 100644
--- a/src/codegen/php/statement_list.rs
+++ b/src/codegen/php/statement_list.rs
@@ -8,7 +8,7 @@ impl Transpilable for PFile<'_> {
             fragments.push(statement.transpile());
         }
 
-        fragments.join("")
+        fragments.join("\n")
     }
 }
 
@@ -37,6 +37,6 @@ mod tests {
         };
         let output = ast.transpile();
 
-        assert_eq!("<?php\n\"Hello world!\";", output);
+        assert_eq!("<?php\n\n\"Hello world!\";", output);
     }
 }
diff --git a/src/php_ast/mod.rs b/src/php_ast/mod.rs
index ef9bde6..11f706a 100644
--- a/src/php_ast/mod.rs
+++ b/src/php_ast/mod.rs
@@ -52,6 +52,7 @@ pub enum PPrimary<'a> {
     IntegerLiteral(&'a String),
     FloatingLiteral(&'a String),
     StringLiteral(&'a String),
+    BoolLiteral(bool),
     /// https://phplang.org/spec/19-grammar.html#grammar-variable
     ///
     /// Supports only variable -> callable-variable -> simple-variable -> variable-name
diff --git a/src/php_ast/transformers/expression.rs b/src/php_ast/transformers/expression.rs
index bf74207..cc2a792 100644
--- a/src/php_ast/transformers/expression.rs
+++ b/src/php_ast/transformers/expression.rs
@@ -32,7 +32,11 @@ impl<'a> PHPTransformable<'a> for Expression<'_> {
                 PExpresssion::FunctionCall(fn_call_expr)
             }
             Expression::Identifier(i) => PExpresssion::Primary(PPrimary::Variable(&i.value)),
-            _ => todo!("transformation for expression: {:?}", self),
+            Expression::Boolean(b) => {
+                PExpresssion::Primary(PPrimary::BoolLiteral(b.value == "true"))
+            }
+            Expression::UnaryOperator(_, _) => unimplemented!("transform unary op into php"),
+            Expression::BinaryOperator(_, _, _) => unimplemented!("transform binary op into php"),
         }
     }
 }
diff --git a/src/semantic/checks/expression.rs b/src/semantic/checks/expression.rs
index 240e492..085e090 100644
--- a/src/semantic/checks/expression.rs
+++ b/src/semantic/checks/expression.rs
@@ -43,7 +43,6 @@ impl SemanticCheck for Expression<'_> {
                                 // The argument and the parameter have diferent types
                                 let (error_start, error_end) = argument.get_position();
                                 return Err(MistiError::Semantic(SemanticError {
-                                    // TODO: fix
                                     error_start,
                                     error_end,
                                     reason: format!(
@@ -67,11 +66,48 @@ impl SemanticCheck for Expression<'_> {
                     }
                 }
             }
+            // These are empty because they have nothing to check,
+            // their existance alone is correct
             Expression::Int(_) => {}
             Expression::Float(_) => {}
             Expression::String(_) => {}
             Expression::Boolean(_) => {}
-            _ => todo!("Check semantics for expression other than function call and primitive"),
+            Expression::Identifier(_) => {}
+            Expression::UnaryOperator(operator, expression) => {
+                // There are a limited amount of unary operators,
+                // so their checking is not generalized
+                let expr_type = expression.get_type(scope)?;
+                match (operator.value.as_str(), expr_type) {
+                    ("!", Type::Value(t)) => {
+                        if t == "Bool" {
+                            // Ok, empty
+                        } else {
+                            // Error: unary negation can only be applied to a Bool
+                            let (error_start, error_end) = expression.get_position();
+                            return Err(MistiError::Semantic(SemanticError {
+                                error_start,
+                                error_end,
+                                reason: format!("Expected a Bool, got a {}", t),
+                            }));
+                        }
+                    }
+                    ("!", Type::Function(_, _)) => {
+                        // Error: unary negation can only be applied to a Bool
+                        let (error_start, error_end) = expression.get_position();
+                        return Err(MistiError::Semantic(SemanticError {
+                            error_start,
+                            error_end,
+                            reason: format!("Expected a Bool, got a function",),
+                        }));
+                    }
+                    (op, _) => {
+                        // Compiler error: something that shouldn't be
+                        // parsed as a unary operator was found.
+                        unreachable!("Found a unary operator that shouldn't be: {}", op)
+                    }
+                }
+            }
+            Expression::BinaryOperator(_, _, _) => unimplemented!(),
         }
 
         Ok(())
diff --git a/src/syntax/parsers/module.rs b/src/syntax/parsers/module.rs
index 623e90a..6647f7e 100644
--- a/src/syntax/parsers/module.rs
+++ b/src/syntax/parsers/module.rs
@@ -1,6 +1,6 @@
 use crate::{
     error_handling::SyntaxError,
-    lexic::token::Token,
+    lexic::token::{Token, TokenType},
     syntax::{
         ast::{Expression, ModuleAST, ModuleMembers, Statement},
         parseable::{Parseable, ParsingError, ParsingResult},
@@ -51,6 +51,16 @@ impl<'a> Parseable<'a> for ModuleAST<'a> {
                 _ => {}
             }
 
+            // Ignore comments, if any
+            if let Some(s) = tokens.get(current_pos) {
+                if s.token_type == TokenType::Comment
+                || s.token_type == TokenType::MultilineComment
+                {
+                    current_pos += 1;
+                    continue;
+                }
+            }
+
             // If we reached this point we didn't match any productions and fail
             let t = &tokens[current_pos];