diff --git a/pil_analyzer/src/expression_processor.rs b/pil_analyzer/src/expression_processor.rs
new file mode 100644
index 000000000..089add6cd
--- /dev/null
+++ b/pil_analyzer/src/expression_processor.rs
@@ -0,0 +1,181 @@
+use std::collections::HashMap;
+
+use ast::{
+    analyzed::{Expression, PolynomialReference, Reference, RepeatedArray},
+    parsed::{
+        self, ArrayExpression, ArrayLiteral, LambdaExpression, MatchArm, MatchPattern,
+        NamespacedPolynomialReference, SelectedExpressions,
+    },
+};
+use number::DegreeType;
+
+/// The ExpressionProcessor turns parsed expressions into analyzed expressions.
+/// Its main job is to resolve references:
+/// It turns simple references into fully namespaced references and resolves local function variables.
+/// It also evaluates expressions that are required to be compile-time constant.
+pub struct ExpressionProcessor<R: ReferenceResolver> {
+    resolver: R,
+    local_variables: HashMap<String, u64>,
+}
+
+pub trait ReferenceResolver {
+    /// Turns a reference to a name with an optional namespace to an absolute name.
+    fn resolve(&self, namespace: &Option<String>, name: &str) -> String;
+}
+
+impl<R: ReferenceResolver> ExpressionProcessor<R> {
+    pub fn new(resolver: R) -> Self {
+        Self {
+            resolver,
+            local_variables: Default::default(),
+        }
+    }
+
+    pub fn process_selected_expression<T>(
+        &mut self,
+        expr: SelectedExpressions<parsed::Expression<T>>,
+    ) -> SelectedExpressions<Expression<T>> {
+        SelectedExpressions {
+            selector: expr.selector.map(|e| self.process_expression(e)),
+            expressions: self.process_expressions(expr.expressions),
+        }
+    }
+
+    pub fn process_array_expression<T>(
+        &mut self,
+        array_expression: ::ast::parsed::ArrayExpression<T>,
+        size: DegreeType,
+    ) -> Vec<RepeatedArray<T>> {
+        match array_expression {
+            ArrayExpression::Value(expressions) => {
+                let values = self.process_expressions(expressions);
+                let size = values.len() as DegreeType;
+                vec![RepeatedArray::new(values, size)]
+            }
+            ArrayExpression::RepeatedValue(expressions) => {
+                if size == 0 {
+                    vec![]
+                } else {
+                    vec![RepeatedArray::new(
+                        self.process_expressions(expressions),
+                        size,
+                    )]
+                }
+            }
+            ArrayExpression::Concat(left, right) => self
+                .process_array_expression(*left, size)
+                .into_iter()
+                .chain(self.process_array_expression(*right, size))
+                .collect(),
+        }
+    }
+
+    pub fn process_expressions<T>(
+        &mut self,
+        exprs: Vec<parsed::Expression<T>>,
+    ) -> Vec<Expression<T>> {
+        exprs
+            .into_iter()
+            .map(|e| self.process_expression(e))
+            .collect()
+    }
+
+    pub fn process_expression<T>(&mut self, expr: parsed::Expression<T>) -> Expression<T> {
+        use parsed::Expression as PExpression;
+        match expr {
+            PExpression::Reference(poly) => Expression::Reference(self.process_reference(poly)),
+            PExpression::PublicReference(name) => Expression::PublicReference(name),
+            PExpression::Number(n) => Expression::Number(n),
+            PExpression::String(value) => Expression::String(value),
+            PExpression::Tuple(items) => Expression::Tuple(self.process_expressions(items)),
+            PExpression::ArrayLiteral(ArrayLiteral { items }) => {
+                Expression::ArrayLiteral(ArrayLiteral {
+                    items: self.process_expressions(items),
+                })
+            }
+            PExpression::LambdaExpression(LambdaExpression { params, body }) => {
+                let body = Box::new(self.process_function(&params, *body));
+                Expression::LambdaExpression(LambdaExpression { params, body })
+            }
+            PExpression::BinaryOperation(left, op, right) => Expression::BinaryOperation(
+                Box::new(self.process_expression(*left)),
+                op,
+                Box::new(self.process_expression(*right)),
+            ),
+            PExpression::UnaryOperation(op, value) => {
+                Expression::UnaryOperation(op, Box::new(self.process_expression(*value)))
+            }
+            PExpression::IndexAccess(index_access) => {
+                Expression::IndexAccess(parsed::IndexAccess {
+                    array: Box::new(self.process_expression(*index_access.array)),
+                    index: Box::new(self.process_expression(*index_access.index)),
+                })
+            }
+            PExpression::FunctionCall(c) => Expression::FunctionCall(parsed::FunctionCall {
+                function: Box::new(self.process_expression(*c.function)),
+                arguments: self.process_expressions(c.arguments),
+            }),
+            PExpression::MatchExpression(scrutinee, arms) => Expression::MatchExpression(
+                Box::new(self.process_expression(*scrutinee)),
+                arms.into_iter()
+                    .map(|MatchArm { pattern, value }| MatchArm {
+                        pattern: match pattern {
+                            MatchPattern::CatchAll => MatchPattern::CatchAll,
+                            MatchPattern::Pattern(e) => {
+                                MatchPattern::Pattern(self.process_expression(e))
+                            }
+                        },
+                        value: self.process_expression(value),
+                    })
+                    .collect(),
+            ),
+            PExpression::FreeInput(_) => panic!(),
+        }
+    }
+
+    fn process_reference(&mut self, reference: NamespacedPolynomialReference) -> Reference {
+        if reference.namespace.is_none() && self.local_variables.contains_key(&reference.name) {
+            let id = self.local_variables[&reference.name];
+            Reference::LocalVar(id, reference.name.to_string())
+        } else {
+            Reference::Poly(self.process_namespaced_polynomial_reference(reference))
+        }
+    }
+
+    pub fn process_function<T>(
+        &mut self,
+        params: &[String],
+        expression: ::ast::parsed::Expression<T>,
+    ) -> Expression<T> {
+        let previous_local_vars = std::mem::take(&mut self.local_variables);
+
+        assert!(self.local_variables.is_empty());
+        self.local_variables = params
+            .iter()
+            .enumerate()
+            .map(|(i, p)| (p.clone(), i as u64))
+            .collect();
+        // Re-add the outer local variables if we do not overwrite them
+        // and increase their index by the number of parameters.
+        // TODO re-evaluate if this mechanism makes sense as soon as we properly
+        // support nested functions and closures.
+        for (name, index) in &previous_local_vars {
+            self.local_variables
+                .entry(name.clone())
+                .or_insert(index + params.len() as u64);
+        }
+        let processed_value = self.process_expression(expression);
+        self.local_variables = previous_local_vars;
+        processed_value
+    }
+
+    pub fn process_namespaced_polynomial_reference(
+        &mut self,
+        poly: ::ast::parsed::NamespacedPolynomialReference,
+    ) -> PolynomialReference {
+        PolynomialReference {
+            name: self.resolver.resolve(&poly.namespace, &poly.name),
+            poly_id: None,
+        }
+    }
+}
diff --git a/pil_analyzer/src/lib.rs b/pil_analyzer/src/lib.rs
index 9ce37c432..1d654f89e 100644
--- a/pil_analyzer/src/lib.rs
+++ b/pil_analyzer/src/lib.rs
@@ -2,6 +2,7 @@
 
 mod condenser;
 pub mod evaluator;
+pub mod expression_processor;
 pub mod pil_analyzer;
 
 use std::path::Path;
diff --git a/pil_analyzer/src/pil_analyzer.rs b/pil_analyzer/src/pil_analyzer.rs
index 402e37196..1dd59684a 100644
--- a/pil_analyzer/src/pil_analyzer.rs
+++ b/pil_analyzer/src/pil_analyzer.rs
@@ -6,19 +6,18 @@ use analysis::MacroExpander;
 
 use ast::parsed::visitor::ExpressionVisitable;
 use ast::parsed::{
-    self, ArrayExpression, ArrayLiteral, FunctionDefinition, LambdaExpression, MatchArm,
-    MatchPattern, NamespacedPolynomialReference, PilStatement, PolynomialName, SelectedExpressions,
+    self, FunctionDefinition, LambdaExpression, PilStatement, PolynomialName, SelectedExpressions,
 };
 use number::{DegreeType, FieldElement};
 
 use ast::analyzed::{
     AlgebraicExpression, Analyzed, Expression, FunctionValueDefinition, Identity, IdentityKind,
-    PolynomialReference, PolynomialType, PublicDeclaration, Reference, RepeatedArray, SourceRef,
-    StatementIdentifier, Symbol, SymbolKind,
+    PolynomialType, PublicDeclaration, SourceRef, StatementIdentifier, Symbol, SymbolKind,
 };
 
 use crate::evaluator::EvalError;
-use crate::{condenser, evaluator};
+use crate::expression_processor::ReferenceResolver;
+use crate::{condenser, evaluator, expression_processor::ExpressionProcessor};
 
 pub fn process_pil_file<T: FieldElement>(path: &Path) -> Analyzed<T> {
     let mut analyzer = PILAnalyzer::new();
@@ -258,25 +257,28 @@ impl<T: FieldElement> PILAnalyzer<T> {
             PilStatement::PlookupIdentity(start, key, haystack) => (
                 start,
                 IdentityKind::Plookup,
-                ExpressionProcessor::new(self).process_selected_expression(key),
-                ExpressionProcessor::new(self).process_selected_expression(haystack),
+                self.expression_processor().process_selected_expression(key),
+                self.expression_processor()
+                    .process_selected_expression(haystack),
             ),
             PilStatement::PermutationIdentity(start, left, right) => (
                 start,
                 IdentityKind::Permutation,
-                ExpressionProcessor::new(self).process_selected_expression(left),
-                ExpressionProcessor::new(self).process_selected_expression(right),
+                self.expression_processor()
+                    .process_selected_expression(left),
+                self.expression_processor()
+                    .process_selected_expression(right),
             ),
             PilStatement::ConnectIdentity(start, left, right) => (
                 start,
                 IdentityKind::Connect,
                 SelectedExpressions {
                     selector: None,
-                    expressions: ExpressionProcessor::new(self).process_expressions(left),
+                    expressions: self.expression_processor().process_expressions(left),
                 },
                 SelectedExpressions {
                     selector: None,
-                    expressions: ExpressionProcessor::new(self).process_expressions(right),
+                    expressions: self.expression_processor().process_expressions(right),
                 },
             ),
             // TODO at some point, these should all be caught by the type checker.
@@ -376,7 +378,7 @@ impl<T: FieldElement> PILAnalyzer<T> {
             FunctionDefinition::Query(params, expr) => {
                 assert!(!have_array_size);
                 assert_eq!(symbol_kind, SymbolKind::Poly(PolynomialType::Committed));
-                let body = Box::new(ExpressionProcessor::new(self).process_function(&params, expr));
+                let body = Box::new(self.expression_processor().process_function(&params, expr));
                 FunctionValueDefinition::Query(Expression::LambdaExpression(LambdaExpression {
                     params,
                     body,
@@ -384,8 +386,9 @@ impl<T: FieldElement> PILAnalyzer<T> {
             }
             FunctionDefinition::Array(value) => {
                 let size = value.solve(self.polynomial_degree.unwrap());
-                let expression =
-                    ExpressionProcessor::new(self).process_array_expression(value, size);
+                let expression = self
+                    .expression_processor()
+                    .process_array_expression(value, size);
                 assert_eq!(
                     expression.iter().map(|e| e.size()).sum::<DegreeType>(),
                     self.polynomial_degree.unwrap()
@@ -412,8 +415,9 @@ impl<T: FieldElement> PILAnalyzer<T> {
         index: parsed::Expression<T>,
     ) {
         let id = self.public_declarations.len() as u64;
-        let polynomial =
-            ExpressionProcessor::new(self).process_namespaced_polynomial_reference(poly);
+        let polynomial = self
+            .expression_processor()
+            .process_namespaced_polynomial_reference(poly);
         let array_index = array_index.map(|i| {
             let index = self.evaluate_expression(i).unwrap().to_degree();
             assert!(index <= usize::MAX as u64);
@@ -445,186 +449,30 @@ impl<T: FieldElement> PILAnalyzer<T> {
         format!("{}.{name}", self.namespace)
     }
 
-    pub fn namespaced_ref_to_absolute(&self, namespace: &Option<String>, name: &str) -> String {
-        if name.starts_with('%') || self.definitions.contains_key(&name.to_string()) {
-            assert!(namespace.is_none());
-            // Constants are not namespaced
-            name.to_string()
-        } else {
-            format!("{}.{name}", namespace.as_ref().unwrap_or(&self.namespace))
-        }
-    }
-
     fn evaluate_expression(&self, expr: ::ast::parsed::Expression<T>) -> Result<T, EvalError> {
         evaluator::evaluate_expression(&self.process_expression(expr), &self.definitions)?
             .try_to_number()
     }
 
+    fn expression_processor(&self) -> ExpressionProcessor<PILResolver<T>> {
+        ExpressionProcessor::new(PILResolver(self))
+    }
+
     fn process_expression(&self, expr: ::ast::parsed::Expression<T>) -> Expression<T> {
-        ExpressionProcessor::new(self).process_expression(expr)
+        self.expression_processor().process_expression(expr)
     }
 }
 
-/// The ExpressionProcessor turns parsed expressions into analyzed expressions.
-/// Its main job is to resolve references:
-/// It turns simple references into fully namespaced references and resolves local function variables.
-/// It also evaluates expressions that are required to be compile-time constant.
-struct ExpressionProcessor<'a, T> {
-    analyzer: &'a PILAnalyzer<T>,
-    local_variables: HashMap<String, u64>,
-}
+struct PILResolver<'a, T>(&'a PILAnalyzer<T>);
 
-impl<'a, T: FieldElement> ExpressionProcessor<'a, T> {
-    fn new(analyzer: &'a PILAnalyzer<T>) -> Self {
-        Self {
-            analyzer,
-            local_variables: Default::default(),
-        }
-    }
-
-    pub fn process_selected_expression(
-        &mut self,
-        expr: SelectedExpressions<parsed::Expression<T>>,
-    ) -> SelectedExpressions<Expression<T>> {
-        SelectedExpressions {
-            selector: expr.selector.map(|e| self.process_expression(e)),
-            expressions: self.process_expressions(expr.expressions),
-        }
-    }
-
-    pub fn process_array_expression(
-        &mut self,
-        array_expression: ::ast::parsed::ArrayExpression<T>,
-        size: DegreeType,
-    ) -> Vec<RepeatedArray<T>> {
-        match array_expression {
-            ArrayExpression::Value(expressions) => {
-                let values = self.process_expressions(expressions);
-                let size = values.len() as DegreeType;
-                vec![RepeatedArray::new(values, size)]
-            }
-            ArrayExpression::RepeatedValue(expressions) => {
-                if size == 0 {
-                    vec![]
-                } else {
-                    vec![RepeatedArray::new(
-                        self.process_expressions(expressions),
-                        size,
-                    )]
-                }
-            }
-            ArrayExpression::Concat(left, right) => self
-                .process_array_expression(*left, size)
-                .into_iter()
-                .chain(self.process_array_expression(*right, size))
-                .collect(),
-        }
-    }
-
-    pub fn process_expressions(&mut self, exprs: Vec<parsed::Expression<T>>) -> Vec<Expression<T>> {
-        exprs
-            .into_iter()
-            .map(|e| self.process_expression(e))
-            .collect()
-    }
-
-    pub fn process_expression(&mut self, expr: parsed::Expression<T>) -> Expression<T> {
-        use parsed::Expression as PExpression;
-        match expr {
-            PExpression::Reference(poly) => Expression::Reference(self.process_reference(poly)),
-            PExpression::PublicReference(name) => Expression::PublicReference(name),
-            PExpression::Number(n) => Expression::Number(n),
-            PExpression::String(value) => Expression::String(value),
-            PExpression::Tuple(items) => Expression::Tuple(self.process_expressions(items)),
-            PExpression::ArrayLiteral(ArrayLiteral { items }) => {
-                Expression::ArrayLiteral(ArrayLiteral {
-                    items: self.process_expressions(items),
-                })
-            }
-            PExpression::LambdaExpression(LambdaExpression { params, body }) => {
-                let body = Box::new(self.process_function(&params, *body));
-                Expression::LambdaExpression(LambdaExpression { params, body })
-            }
-            PExpression::BinaryOperation(left, op, right) => Expression::BinaryOperation(
-                Box::new(self.process_expression(*left)),
-                op,
-                Box::new(self.process_expression(*right)),
-            ),
-            PExpression::UnaryOperation(op, value) => {
-                Expression::UnaryOperation(op, Box::new(self.process_expression(*value)))
-            }
-            PExpression::IndexAccess(index_access) => {
-                Expression::IndexAccess(parsed::IndexAccess {
-                    array: Box::new(self.process_expression(*index_access.array)),
-                    index: Box::new(self.process_expression(*index_access.index)),
-                })
-            }
-            PExpression::FunctionCall(c) => Expression::FunctionCall(parsed::FunctionCall {
-                function: Box::new(self.process_expression(*c.function)),
-                arguments: self.process_expressions(c.arguments),
-            }),
-            PExpression::MatchExpression(scrutinee, arms) => Expression::MatchExpression(
-                Box::new(self.process_expression(*scrutinee)),
-                arms.into_iter()
-                    .map(|MatchArm { pattern, value }| MatchArm {
-                        pattern: match pattern {
-                            MatchPattern::CatchAll => MatchPattern::CatchAll,
-                            MatchPattern::Pattern(e) => {
-                                MatchPattern::Pattern(self.process_expression(e))
-                            }
-                        },
-                        value: self.process_expression(value),
-                    })
-                    .collect(),
-            ),
-            PExpression::FreeInput(_) => panic!(),
-        }
-    }
-
-    fn process_reference(&mut self, reference: NamespacedPolynomialReference) -> Reference {
-        if reference.namespace.is_none() && self.local_variables.contains_key(&reference.name) {
-            let id = self.local_variables[&reference.name];
-            Reference::LocalVar(id, reference.name.to_string())
+impl<'a, T: FieldElement> ReferenceResolver for PILResolver<'a, T> {
+    fn resolve(&self, namespace: &Option<String>, name: &str) -> String {
+        if name.starts_with('%') || self.0.definitions.contains_key(&name.to_string()) {
+            assert!(namespace.is_none());
+            // Constants are not namespaced
+            name.to_string()
         } else {
-            Reference::Poly(self.process_namespaced_polynomial_reference(reference))
-        }
-    }
-
-    fn process_function(
-        &mut self,
-        params: &[String],
-        expression: ::ast::parsed::Expression<T>,
-    ) -> Expression<T> {
-        let previous_local_vars = std::mem::take(&mut self.local_variables);
-
-        assert!(self.local_variables.is_empty());
-        self.local_variables = params
-            .iter()
-            .enumerate()
-            .map(|(i, p)| (p.clone(), i as u64))
-            .collect();
-        // Re-add the outer local variables if we do not overwrite them
-        // and increase their index by the number of parameters.
-        for (name, index) in &previous_local_vars {
-            self.local_variables
-                .entry(name.clone())
-                .or_insert(index + params.len() as u64);
-        }
-        let processed_value = self.process_expression(expression);
-        self.local_variables = previous_local_vars;
-        processed_value
-    }
-
-    pub fn process_namespaced_polynomial_reference(
-        &mut self,
-        poly: ::ast::parsed::NamespacedPolynomialReference,
-    ) -> PolynomialReference {
-        let name = self
-            .analyzer
-            .namespaced_ref_to_absolute(&poly.namespace, &poly.name);
-        PolynomialReference {
-            name,
-            poly_id: None,
+            format!("{}.{name}", namespace.as_ref().unwrap_or(&self.0.namespace))
         }
     }
 }