diff --git a/simple.program b/simple.program
index ff20c799e5..fc22903370 100644
--- a/simple.program
+++ b/simple.program
@@ -2,4 +2,6 @@ struct Foo {
     field a
     bool b
 }
-return 1
\ No newline at end of file
+def main() -> (field) :
+    a = 1 + 1
+    return a
\ No newline at end of file
diff --git a/src/aleo_program/constraints.rs b/src/aleo_program/constraints.rs
index 0a24a301b0..1682b9b160 100644
--- a/src/aleo_program/constraints.rs
+++ b/src/aleo_program/constraints.rs
@@ -1,5 +1,5 @@
 use crate::aleo_program::{
-    BooleanExpression, Expression, FieldExpression, Program, Statement, Variable,
+    BooleanExpression, Expression, FieldExpression, Function, Program, Statement, Struct, Variable,
 };
 
 use snarkos_models::curves::{Field, PrimeField};
@@ -14,6 +14,8 @@ use std::collections::HashMap;
 pub enum ResolvedValue {
     Boolean(Boolean),
     FieldElement(UInt32),
+    Struct(Struct),
+    Function(Function),
 }
 
 pub struct ResolvedProgram {
@@ -315,115 +317,141 @@ impl ResolvedProgram {
         }
     }
 
+    fn enforce_statement<F: Field + PrimeField, CS: ConstraintSystem<F>>(
+        &mut self,
+        cs: &mut CS,
+        statement: Statement,
+    ) {
+        match statement {
+            Statement::Definition(variable, expression) => match expression {
+                Expression::Boolean(boolean_expression) => {
+                    let res = self.enforce_boolean_expression(cs, boolean_expression);
+                    println!(
+                        " variable boolean result: {} = {}",
+                        variable.0,
+                        res.get_value().unwrap()
+                    );
+                    self.insert(variable, ResolvedValue::Boolean(res));
+                }
+                Expression::FieldElement(field_expression) => {
+                    let res = self.enforce_field_expression(cs, field_expression);
+                    println!(
+                        " variable field result: {} = {}",
+                        variable.0,
+                        res.value.unwrap()
+                    );
+                    self.insert(variable, ResolvedValue::FieldElement(res));
+                }
+                Expression::Variable(unresolved_variable) => {
+                    if self.resolved_variables.contains_key(&unresolved_variable) {
+                        // Reassigning variable to another variable
+                        let already_assigned = self
+                            .resolved_variables
+                            .get_mut(&unresolved_variable)
+                            .unwrap()
+                            .clone();
+                        self.insert(variable, already_assigned);
+                    } else {
+                        // The type of the unassigned variable depends on what is passed in
+                        if std::env::args()
+                            .nth(1)
+                            .expect("variable declaration not passed in")
+                            .parse::<bool>()
+                            .is_ok()
+                        {
+                            let resolved_boolean = self.bool_from_variable(cs, unresolved_variable);
+                            println!(
+                                "variable boolean result: {} = {}",
+                                variable.0,
+                                resolved_boolean.get_value().unwrap()
+                            );
+                            self.insert(variable, ResolvedValue::Boolean(resolved_boolean));
+                        } else {
+                            let resolved_field_element =
+                                self.u32_from_variable(cs, unresolved_variable);
+                            println!(
+                                " variable field result: {} = {}",
+                                variable.0,
+                                resolved_field_element.value.unwrap()
+                            );
+                            self.insert(
+                                variable,
+                                ResolvedValue::FieldElement(resolved_field_element),
+                            );
+                        }
+                    }
+                }
+            },
+            Statement::Return(statements) => {
+                statements
+                    .into_iter()
+                    .for_each(|expression| match expression {
+                        Expression::Boolean(boolean_expression) => {
+                            let res = self.enforce_boolean_expression(cs, boolean_expression);
+                            println!("\n  Boolean result = {}", res.get_value().unwrap());
+                        }
+                        Expression::FieldElement(field_expression) => {
+                            let res = self.enforce_field_expression(cs, field_expression);
+                            println!("\n  Field result = {}", res.value.unwrap());
+                        }
+                        Expression::Variable(variable) => {
+                            match self.resolved_variables.get_mut(&variable).unwrap().clone() {
+                                ResolvedValue::Boolean(boolean) => println!(
+                                    "\n  Variable result = {}",
+                                    boolean.get_value().unwrap()
+                                ),
+                                ResolvedValue::FieldElement(field_element) => println!(
+                                    "\n  Variable field result = {}",
+                                    field_element.value.unwrap()
+                                ),
+                                _ => {}
+                            }
+                        }
+                    });
+            }
+        };
+    }
+
     pub fn generate_constraints<F: Field + PrimeField, CS: ConstraintSystem<F>>(
         cs: &mut CS,
         program: Program,
     ) {
         let mut resolved_program = ResolvedProgram::new();
 
+        program
+            .structs
+            .into_iter()
+            .for_each(|(variable, struct_def)| {
+                resolved_program
+                    .resolved_variables
+                    .insert(variable, ResolvedValue::Struct(struct_def));
+            });
+        program
+            .functions
+            .into_iter()
+            .for_each(|(variable, function)| {
+                resolved_program
+                    .resolved_variables
+                    .insert(variable, ResolvedValue::Function(function));
+            });
+
+        let main = resolved_program
+            .resolved_variables
+            .get_mut(&Variable("main".into()))
+            .expect("main function not defined");
+        match main {
+            ResolvedValue::Function(function) => function
+                .statements
+                .clone()
+                .into_iter()
+                .for_each(|statement| resolved_program.enforce_statement(cs, statement)),
+            _ => unimplemented!("main must be a function"),
+        }
+
         program
             .statements
             .into_iter()
-            .for_each(|statement| match statement {
-                Statement::Definition(variable, expression) => match expression {
-                    Expression::Boolean(boolean_expression) => {
-                        let res =
-                            resolved_program.enforce_boolean_expression(cs, boolean_expression);
-                        println!(
-                            " variable boolean result: {} = {}",
-                            variable.0,
-                            res.get_value().unwrap()
-                        );
-                        resolved_program.insert(variable, ResolvedValue::Boolean(res));
-                    }
-                    Expression::FieldElement(field_expression) => {
-                        let res = resolved_program.enforce_field_expression(cs, field_expression);
-                        println!(
-                            " variable field result: {} = {}",
-                            variable.0,
-                            res.value.unwrap()
-                        );
-                        resolved_program.insert(variable, ResolvedValue::FieldElement(res));
-                    }
-                    Expression::Variable(unresolved_variable) => {
-                        if resolved_program
-                            .resolved_variables
-                            .contains_key(&unresolved_variable)
-                        {
-                            // Reassigning variable to another variable
-                            let already_assigned = resolved_program
-                                .resolved_variables
-                                .get_mut(&unresolved_variable)
-                                .unwrap()
-                                .clone();
-                            resolved_program.insert(variable, already_assigned);
-                        } else {
-                            // The type of the unassigned variable depends on what is passed in
-                            if std::env::args()
-                                .nth(1)
-                                .expect("variable declaration not passed in")
-                                .parse::<bool>()
-                                .is_ok()
-                            {
-                                let resolved_boolean =
-                                    resolved_program.bool_from_variable(cs, unresolved_variable);
-                                println!(
-                                    "variable boolean result: {} = {}",
-                                    variable.0,
-                                    resolved_boolean.get_value().unwrap()
-                                );
-                                resolved_program
-                                    .insert(variable, ResolvedValue::Boolean(resolved_boolean));
-                            } else {
-                                let resolved_field_element =
-                                    resolved_program.u32_from_variable(cs, unresolved_variable);
-                                println!(
-                                    " variable field result: {} = {}",
-                                    variable.0,
-                                    resolved_field_element.value.unwrap()
-                                );
-                                resolved_program.insert(
-                                    variable,
-                                    ResolvedValue::FieldElement(resolved_field_element),
-                                );
-                            }
-                        }
-                    }
-                },
-                Statement::Return(statements) => {
-                    statements
-                        .into_iter()
-                        .for_each(|expression| match expression {
-                            Expression::Boolean(boolean_expression) => {
-                                let res = resolved_program
-                                    .enforce_boolean_expression(cs, boolean_expression);
-                                println!("\n  Boolean result = {}", res.get_value().unwrap());
-                            }
-                            Expression::FieldElement(field_expression) => {
-                                let res =
-                                    resolved_program.enforce_field_expression(cs, field_expression);
-                                println!("\n  Field result = {}", res.value.unwrap());
-                            }
-                            Expression::Variable(variable) => {
-                                match resolved_program
-                                    .resolved_variables
-                                    .get_mut(&variable)
-                                    .unwrap()
-                                    .clone()
-                                {
-                                    ResolvedValue::Boolean(boolean) => println!(
-                                        "\n  Variable result = {}",
-                                        boolean.get_value().unwrap()
-                                    ),
-                                    ResolvedValue::FieldElement(field_element) => println!(
-                                        "\n  Variable field result = {}",
-                                        field_element.value.unwrap()
-                                    ),
-                                }
-                            }
-                        });
-                }
-            });
+            .for_each(|statement| resolved_program.enforce_statement(cs, statement));
     }
 }
 
diff --git a/src/aleo_program/types.rs b/src/aleo_program/types.rs
index decd976411..f7adc59e34 100644
--- a/src/aleo_program/types.rs
+++ b/src/aleo_program/types.rs
@@ -4,29 +4,11 @@
 //! @author Collin Chin <collin@aleo.org>
 //! @date 2020
 
-// id == 0 for field values
-// id < 0 for boolean values
+use std::collections::HashMap;
+
 /// A variable in a constraint system.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Variable(pub String);
-//
-// /// Linear combination of variables in a program. (a + b + c)
-// #[derive(Debug, Clone)]
-// pub struct LinearCombination (pub Vec<Variable>);
-//
-// impl LinearCombination {
-//     pub fn one() -> Self {
-//         LinearCombination(vec![Variable{ id: 0, value: "1".into() }])
-//     }
-//
-//     pub fn value(&self) -> String {
-//         self.0[0].value.clone()
-//     }
-// }
-//
-// /// Quadratic combination of variables in a program (a * b)
-// #[derive(Debug, Clone)]
-// pub struct QuadraticCombination (pub LinearCombination, pub LinearCombination);
 
 /// Expression that evaluates to a field value
 #[derive(Debug, Clone)]
@@ -109,11 +91,33 @@ pub struct Struct {
     pub fields: Vec<StructField>,
 }
 
+#[derive(Clone, Debug)]
+pub enum Visibility {
+    Public,
+    Private,
+}
+
+#[derive(Clone, Debug)]
+pub struct Parameter {
+    pub visibility: Option<Visibility>,
+    pub ty: Type,
+    pub variable: Variable,
+}
+
+#[derive(Clone, Debug)]
+pub struct Function {
+    pub variable: Variable,
+    pub parameters: Vec<Parameter>,
+    pub returns: Vec<Type>,
+    pub statements: Vec<Statement>,
+}
+
 /// A simple program with statement expressions, program arguments and program returns.
 #[derive(Debug, Clone)]
 pub struct Program {
     pub id: String,
-    pub structs: Vec<Struct>,
+    pub structs: HashMap<Variable, Struct>,
+    pub functions: HashMap<Variable, Function>,
     pub statements: Vec<Statement>,
     pub arguments: Vec<Variable>,
     pub returns: Vec<Variable>,
diff --git a/src/aleo_program/types_from.rs b/src/aleo_program/types_from.rs
index d4029a9e0a..88f67a13eb 100644
--- a/src/aleo_program/types_from.rs
+++ b/src/aleo_program/types_from.rs
@@ -6,6 +6,7 @@
 //! @date 2020
 
 use crate::{aleo_program::types, ast};
+use std::collections::HashMap;
 
 impl<'ast> From<ast::Field<'ast>> for types::FieldExpression {
     fn from(field: ast::Field<'ast>) -> Self {
@@ -341,8 +342,8 @@ impl<'ast> From<ast::Statement<'ast>> for types::Statement {
 impl<'ast> From<ast::BasicType<'ast>> for types::Type {
     fn from(basic_type: ast::BasicType<'ast>) -> Self {
         match basic_type {
-            ast::BasicType::Field(ty) => types::Type::FieldElement,
-            ast::BasicType::Boolean(ty) => types::Type::Boolean,
+            ast::BasicType::Field(_ty) => types::Type::FieldElement,
+            ast::BasicType::Boolean(_ty) => types::Type::Boolean,
         }
     }
 }
@@ -396,20 +397,82 @@ impl<'ast> From<ast::Struct<'ast>> for types::Struct {
     }
 }
 
+impl From<ast::Visibility> for types::Visibility {
+    fn from(visibility: ast::Visibility) -> Self {
+        match visibility {
+            ast::Visibility::Private(_private) => types::Visibility::Private,
+            ast::Visibility::Public(_public) => types::Visibility::Public,
+        }
+    }
+}
+
+impl<'ast> From<ast::Parameter<'ast>> for types::Parameter {
+    fn from(parameter: ast::Parameter<'ast>) -> Self {
+        let ty = types::Type::from(parameter.ty);
+        let variable = types::Variable::from(parameter.variable);
+
+        if parameter.visibility.is_some() {
+            let visibility = Some(types::Visibility::from(parameter.visibility.unwrap()));
+            types::Parameter {
+                visibility,
+                ty,
+                variable,
+            }
+        } else {
+            types::Parameter {
+                visibility: None,
+                ty,
+                variable,
+            }
+        }
+    }
+}
+
+impl<'ast> From<ast::Function<'ast>> for types::Function {
+    fn from(function_definition: ast::Function<'ast>) -> Self {
+        let variable = types::Variable::from(function_definition.variable);
+        let parameters = function_definition
+            .parameters
+            .into_iter()
+            .map(|parameter| types::Parameter::from(parameter))
+            .collect();
+        let returns = function_definition
+            .returns
+            .into_iter()
+            .map(|return_type| types::Type::from(return_type))
+            .collect();
+        let statements = function_definition
+            .statements
+            .into_iter()
+            .map(|statement| types::Statement::from(statement))
+            .collect();
+
+        types::Function {
+            variable,
+            parameters,
+            returns,
+            statements,
+        }
+    }
+}
+
 impl<'ast> From<ast::File<'ast>> for types::Program {
     fn from(file: ast::File<'ast>) -> Self {
         // 1. compile ast -> aleo program representation
-        let structs = file
-            .structs
-            .into_iter()
-            .map(|struct_def| {
-                println!("{:#?}", struct_def);
-                types::Struct::from(struct_def)
-            })
-            .collect();
-        file.functions
-            .into_iter()
-            .for_each(|function_def| println!("{:#?}", function_def));
+        let mut structs = HashMap::new();
+        let mut functions = HashMap::new();
+
+        file.structs.into_iter().for_each(|struct_def| {
+            println!("{:#?}", struct_def);
+            let struct_definition = types::Struct::from(struct_def);
+            structs.insert(struct_definition.variable.clone(), struct_definition);
+        });
+        file.functions.into_iter().for_each(|function_def| {
+            println!("{:#?}", function_def);
+            let function_definition = types::Function::from(function_def);
+            functions.insert(function_definition.variable.clone(), function_definition);
+        });
+
         let statements: Vec<types::Statement> = file
             .statements
             .into_iter()
@@ -419,6 +482,7 @@ impl<'ast> From<ast::File<'ast>> for types::Program {
         types::Program {
             id: "main".into(),
             structs,
+            functions,
             statements,
             arguments: vec![],
             returns: vec![],
diff --git a/src/ast.rs b/src/ast.rs
index 731cb6944a..e2b358c1fc 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -408,20 +408,20 @@ pub struct ArrayAccess<'ast> {
     pub span: Span<'ast>,
 }
 
-// #[derive(Clone, Debug, FromPest, PartialEq)]
-// #[pest_ast(rule(Rule::member_access))]
-// pub struct MemberAccess<'ast> {
-//     pub id: IdentifierExpression<'ast>,
-//     #[pest_ast(outer())]
-//     pub span: Span<'ast>,
-// }
+#[derive(Clone, Debug, FromPest, PartialEq)]
+#[pest_ast(rule(Rule::access_member))]
+pub struct MemberAccess<'ast> {
+    pub variable: Variable<'ast>,
+    #[pest_ast(outer())]
+    pub span: Span<'ast>,
+}
 
 #[derive(Clone, Debug, FromPest, PartialEq)]
 #[pest_ast(rule(Rule::access))]
 pub enum Access<'ast> {
     // Call(CallAccess<'ast>),
     Select(ArrayAccess<'ast>),
-    // Member(MemberAccess<'ast>),
+    Member(MemberAccess<'ast>),
 }
 
 #[derive(Clone, Debug, FromPest, PartialEq)]