diff --git a/simple.program b/simple.program
index dd5f5ba1e8..39835d769f 100644
--- a/simple.program
+++ b/simple.program
@@ -1,6 +1,9 @@
 struct Foo {
     bool x
 }
-def main() -> (bool):
-    Foo f = Foo {x: true}
-    return f.x
+def main() -> (field):
+  field[3] a = [1, 2, 3] 	 		     // initialize the array
+  field[4] b = [42; 4]
+  c = a[1..3] // helloo???
+  bool[3] d = [true, false, true]
+  return a[0]
diff --git a/src/aleo_program/constraints.rs b/src/aleo_program/constraints.rs
index 0c753648a6..f2304c8488 100644
--- a/src/aleo_program/constraints.rs
+++ b/src/aleo_program/constraints.rs
@@ -742,10 +742,10 @@ impl ResolvedProgram {
         program
             .functions
             .into_iter()
-            .for_each(|(variable, function)| {
+            .for_each(|(function_name, function)| {
                 resolved_program
                     .resolved_variables
-                    .insert(variable, ResolvedValue::Function(function));
+                    .insert(Variable(function_name.0), ResolvedValue::Function(function));
             });
 
         let main = resolved_program
diff --git a/src/aleo_program/types.rs b/src/aleo_program/types.rs
index 3f61518019..6b099c102e 100644
--- a/src/aleo_program/types.rs
+++ b/src/aleo_program/types.rs
@@ -151,9 +151,13 @@ pub struct Parameter {
     pub variable: Variable,
 }
 
+/// The given name for a defined function in the program.
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct FunctionName(pub String);
+
 #[derive(Clone)]
 pub struct Function {
-    pub variable: Variable,
+    pub function_name: FunctionName,
     pub parameters: Vec<Parameter>,
     pub returns: Vec<Type>,
     pub statements: Vec<Statement>,
@@ -164,7 +168,7 @@ pub struct Function {
 pub struct Program {
     pub id: String,
     pub structs: HashMap<Variable, Struct>,
-    pub functions: HashMap<Variable, Function>,
+    pub functions: HashMap<FunctionName, Function>,
     // pub statements: Vec<Statement>,
     pub arguments: Vec<Variable>,
     pub returns: Vec<Variable>,
diff --git a/src/aleo_program/types_display.rs b/src/aleo_program/types_display.rs
index 617557978a..f27dcc86ce 100644
--- a/src/aleo_program/types_display.rs
+++ b/src/aleo_program/types_display.rs
@@ -6,7 +6,7 @@
 
 use crate::aleo_program::{
     BooleanExpression, BooleanSpread, BooleanSpreadOrExpression, Expression, FieldExpression,
-    FieldRangeOrExpression, FieldSpread, FieldSpreadOrExpression, Function, Parameter, Statement,
+    FieldRangeOrExpression, FieldSpread, FieldSpreadOrExpression, Function, FunctionName, Parameter, Statement,
     Struct, StructField, Type, Variable,
 };
 
@@ -241,6 +241,12 @@ impl fmt::Debug for Parameter {
     }
 }
 
+impl fmt::Debug for FunctionName {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
 impl fmt::Display for Function {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
diff --git a/src/aleo_program/types_from.rs b/src/aleo_program/types_from.rs
index 8ba951c389..0db8ffe941 100644
--- a/src/aleo_program/types_from.rs
+++ b/src/aleo_program/types_from.rs
@@ -668,9 +668,15 @@ impl<'ast> From<ast::Parameter<'ast>> for types::Parameter {
     }
 }
 
+impl<'ast> From<ast::FunctionName<'ast>> for types::FunctionName {
+    fn from(name: ast::FunctionName<'ast>) -> Self {
+        types::FunctionName(name.value)
+    }
+}
+
 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 function_name = types::FunctionName::from(function_definition.function_name);
         let parameters = function_definition
             .parameters
             .into_iter()
@@ -688,7 +694,7 @@ impl<'ast> From<ast::Function<'ast>> for types::Function {
             .collect();
 
         types::Function {
-            variable,
+            function_name,
             parameters,
             returns,
             statements,
@@ -710,7 +716,7 @@ impl<'ast> From<ast::File<'ast>> for types::Program {
         });
         file.functions.into_iter().for_each(|function_def| {
             functions.insert(
-                types::Variable::from(function_def.variable.clone()),
+                types::FunctionName::from(function_def.function_name.clone()),
                 types::Function::from(function_def),
             );
         });
diff --git a/src/ast.rs b/src/ast.rs
index 6fc9dbf50f..4539e63b9d 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -786,10 +786,19 @@ pub struct Parameter<'ast> {
     pub span: Span<'ast>,
 }
 
+#[derive(Clone, Debug, FromPest, PartialEq)]
+#[pest_ast(rule(Rule::function_name))]
+pub struct FunctionName<'ast> {
+    #[pest_ast(outer(with(span_into_string)))]
+    pub value: String,
+    #[pest_ast(outer())]
+    pub span: Span<'ast>,
+}
+
 #[derive(Clone, Debug, FromPest, PartialEq)]
 #[pest_ast(rule(Rule::function_definition))]
 pub struct Function<'ast> {
-    pub variable: Variable<'ast>,
+    pub function_name: FunctionName<'ast>,
     pub parameters: Vec<Parameter<'ast>>,
     pub returns: Vec<Type<'ast>>,
     pub statements: Vec<Statement<'ast>>,
diff --git a/src/language.pest b/src/language.pest
index e06adab820..dd2691ac6f 100644
--- a/src/language.pest
+++ b/src/language.pest
@@ -150,7 +150,9 @@ statement = {
 
 parameter = {visibility? ~ ty ~ variable}
 parameter_list = _{(parameter ~ ("," ~ parameter)*)?}
-function_definition = {"def" ~ variable ~ "(" ~ parameter_list ~ ")" ~ "->" ~ "(" ~ type_list ~ ")" ~ ":" ~ NEWLINE* ~ statement* }
+
+function_name = @{ ((!protected_name ~ ASCII_ALPHA) | (protected_name ~ (ASCII_ALPHANUMERIC | "_"))) ~ (ASCII_ALPHANUMERIC | "_")* }
+function_definition = {"def" ~ function_name ~ "(" ~ parameter_list ~ ")" ~ "->" ~ "(" ~ type_list ~ ")" ~ ":" ~ NEWLINE* ~ statement* }
 
 /// Utilities