diff --git a/src/Makefile.am b/src/Makefile.am
index c6bc49b..f6bba9f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,6 +4,7 @@ lib_LIBRARIES = libapfl.a
 
 libapfl_a_SOURCES =
 libapfl_a_SOURCES += error.c
+libapfl_a_SOURCES += eval.c
 libapfl_a_SOURCES += expr.c
 libapfl_a_SOURCES += internal.c
 libapfl_a_SOURCES += position.c
@@ -13,6 +14,7 @@ libapfl_a_SOURCES += token.c
 libapfl_a_SOURCES += tokenizer.c
 libapfl_a_SOURCES += parser.c
 libapfl_a_SOURCES += source_readers.c
+libapfl_a_SOURCES += value.c
 
 apfl_internal_headers =
 apfl_internal_headers += common.h
diff --git a/src/apfl.h b/src/apfl.h
index a27557f..b279fa8 100644
--- a/src/apfl.h
+++ b/src/apfl.h
@@ -473,6 +473,83 @@ struct apfl_error apfl_parser_get_error(apfl_parser_ptr);
  */
 struct apfl_expr apfl_parser_get_expr(apfl_parser_ptr);
 
+
+struct apfl_ctx_data;
+typedef struct apfl_ctx_data *apfl_ctx;
+
+typedef unsigned apfl_refcount;
+
+struct apfl_list {
+    // TODO: Not sure if it's a good idea to expose this struct?
+
+    apfl_refcount refcount;
+    struct apfl_value *items;
+    size_t len;
+    size_t cap;
+};
+
+
+enum apfl_value_type {
+    APFL_VALUE_NIL,
+    APFL_VALUE_BOOLEAN,
+    APFL_VALUE_NUMBER,
+    APFL_VALUE_STRING,
+    APFL_VALUE_LIST,
+    // TODO: dict, functions/closures
+};
+
+struct apfl_value {
+    enum apfl_value_type type;
+    union {
+        bool boolean;
+        apfl_number number;
+        struct apfl_string string;
+        struct apfl_list *list;
+    };
+};
+
+bool apfl_value_copy(struct apfl_value *dst, struct apfl_value src);
+void apfl_value_print(struct apfl_value, FILE *);
+void apfl_value_deinit(struct apfl_value *);
+
+enum apfl_function_response_type {
+    APFL_FUNCTION_RESPONSE_OK,
+    APFL_FUNCTION_RESPONSE_ERROR,
+};
+
+struct apfl_function_response {
+    enum apfl_function_response_type type;
+    struct apfl_value value;
+};
+
+typedef struct apfl_function_response (*apfl_user_function_cb)(apfl_ctx, struct apfl_list arguments, void *);
+
+struct apfl_user_function {
+    apfl_user_function_cb cb;
+    void *opaque;
+};
+
+
+enum apfl_result_type {
+    APFL_RESULT_OK,
+    APFL_RESULT_ERR,
+    APFL_RESULT_ERR_FATAL,
+};
+
+struct apfl_result {
+    enum apfl_result_type type;
+    struct apfl_value value;
+    // TODO: No further details are yet provided on (fatal) error. Not quite
+    //       sure what to return / how errors/exceptions should work. Maybe a
+    //       value + a backtrace?
+};
+
+apfl_ctx apfl_ctx_new(void);
+
+void apfl_ctx_destroy(apfl_ctx);
+
+struct apfl_result apfl_eval(apfl_ctx, struct apfl_expr);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/eval.c b/src/eval.c
new file mode 100644
index 0000000..a71cc88
--- /dev/null
+++ b/src/eval.c
@@ -0,0 +1,188 @@
+#include <assert.h>
+
+#include "apfl.h"
+#include "internal.h"
+#include "resizable.h"
+
+struct apfl_ctx_data {
+    char nothing_here_yet;
+};
+
+static struct apfl_result evaluate(apfl_ctx, struct apfl_expr *);
+
+apfl_ctx
+apfl_ctx_new()
+{
+    apfl_ctx ctx = ALLOC(struct apfl_ctx_data);
+    if (ctx == NULL) {
+        return NULL;
+    }
+
+    return ctx;
+}
+
+void
+apfl_ctx_destroy(apfl_ctx ctx)
+{
+    free(ctx);
+}
+
+static struct apfl_value
+evaluate_constant(struct apfl_expr_const constant)
+{
+    struct apfl_string str = apfl_string_blank();
+
+    switch (constant.type) {
+    case APFL_EXPR_CONST_NIL:
+        return (struct apfl_value) {
+            .type = APFL_VALUE_NIL,
+        };
+    case APFL_EXPR_CONST_BOOLEAN:
+        return (struct apfl_value) {
+            .type = APFL_VALUE_BOOLEAN,
+            .boolean = constant.boolean,
+        };
+    case APFL_EXPR_CONST_STRING:
+        assert(apfl_string_copy(&str, apfl_string_view_from(constant.string))); // TODO: This can fail!
+        return (struct apfl_value) {
+            .type = APFL_VALUE_STRING,
+            .string = str,
+        };
+    case APFL_EXPR_CONST_NUMBER:
+        return (struct apfl_value) {
+            .type = APFL_VALUE_NUMBER,
+            .number = constant.number,
+        };
+    }
+
+    assert(false);
+}
+
+static struct apfl_result
+evaluate_list_expr_to_list(apfl_ctx ctx, struct apfl_expr *expr, struct apfl_list *out)
+{
+    struct apfl_result result = evaluate(ctx, expr);
+    if (result.type != APFL_RESULT_OK) {
+        return result;
+    }
+
+    if (result.value.type != APFL_VALUE_LIST) {
+        apfl_value_deinit(&result.value);
+        return (struct apfl_result) { .type = APFL_RESULT_ERR };
+    }
+
+    struct apfl_list *list = result.value.list;
+
+    if (!apfl_resizable_ensure_cap_for_more_elements(
+        sizeof(struct apfl_value),
+        (void **)&out->items,
+        out->len,
+        &out->cap,
+        list->len
+    )) {
+        apfl_value_deinit(&result.value);
+        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+    }
+
+    for (size_t i = 0; i < list->len; i++) {
+        if (!apfl_value_copy(&out->items[out->len], list->items[i])) {
+            apfl_value_deinit(&result.value);
+            return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+        }
+        out->len++;
+    }
+
+    apfl_value_deinit(&result.value);
+    return (struct apfl_result) { .type = APFL_RESULT_OK, .value.type = APFL_VALUE_NIL };
+}
+
+static struct apfl_result
+evaluate_expr_list_into_list(apfl_ctx ctx, struct apfl_expr_list *list, struct apfl_list *out)
+{
+    for (size_t i = 0; i < list->len; i++) {
+        struct apfl_expr_list_item *item = &list->items[i];
+
+        if (item->expand) {
+            struct apfl_result result = evaluate_list_expr_to_list(ctx, item->expr, out);
+            if (result.type != APFL_RESULT_OK) {
+                return result;
+            }
+        } else {
+            struct apfl_result result = evaluate(ctx, item->expr);
+            if (result.type != APFL_RESULT_OK) {
+                return result;
+            }
+
+            if (!apfl_resizable_append(
+                sizeof(struct apfl_value),
+                (void **)&out->items,
+                &out->len,
+                &out->cap,
+                &result.value,
+                1
+            )) {
+                apfl_value_deinit(&result.value);
+                return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+            }
+        }
+    }
+
+    return (struct apfl_result) { .type = APFL_RESULT_OK, .value.type = APFL_VALUE_NIL };
+}
+
+static struct apfl_result
+evaluate_list(apfl_ctx ctx, struct apfl_expr_list *list)
+{
+    struct apfl_list *out = apfl_list_new();
+    if (out == NULL) {
+        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+    }
+
+    struct apfl_result result = evaluate_expr_list_into_list(ctx, list, out);
+    if (result.type != APFL_RESULT_OK) {
+        DESTROY(out, apfl_list_deinit);
+        return result;
+    }
+
+    return (struct apfl_result) {
+        .type = APFL_RESULT_OK,
+        .value = {
+            .type = APFL_VALUE_LIST,
+            .list = out,
+        },
+    };
+}
+
+static struct apfl_result
+evaluate(apfl_ctx ctx, struct apfl_expr *expr)
+{
+    (void)ctx;
+    switch (expr->type) {
+    case APFL_EXPR_CONSTANT:
+        return (struct apfl_result) {
+            .type = APFL_RESULT_OK,
+            .value = evaluate_constant(expr->constant),
+        };
+    case APFL_EXPR_LIST:
+        return evaluate_list(ctx, &expr->list);
+    case APFL_EXPR_VAR:
+    case APFL_EXPR_CALL:
+    case APFL_EXPR_DICT:
+    case APFL_EXPR_SIMPLE_FUNC:
+    case APFL_EXPR_COMPLEX_FUNC:
+    case APFL_EXPR_ASSIGNMENT:
+    case APFL_EXPR_DOT:
+    case APFL_EXPR_AT:
+        break; // Not implemented yet
+    }
+
+    return (struct apfl_result) { .type = APFL_RESULT_ERR };
+}
+
+struct apfl_result
+apfl_eval(apfl_ctx ctx, struct apfl_expr expr)
+{
+    struct apfl_result result = evaluate(ctx, &expr);
+    apfl_expr_deinit(&expr);
+    return result;
+}
diff --git a/src/internal.h b/src/internal.h
index da40a92..aa3cb9b 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -45,6 +45,9 @@ extern "C" {
 // Internal use only functions
 
 void apfl_print_indented(unsigned indent, FILE *, const char* fmt, ...);
+struct apfl_list *apfl_list_new(void);
+void apfl_list_deinit(struct apfl_list *);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/value.c b/src/value.c
new file mode 100644
index 0000000..c136516
--- /dev/null
+++ b/src/value.c
@@ -0,0 +1,133 @@
+#include <assert.h>
+
+#include "apfl.h"
+#include "internal.h"
+
+/**
+ * Decrease a refererence count. Returns true, if the object should be freed.
+ */
+static bool
+dec_refcount(unsigned *rc)
+{
+    if (rc == 0) {
+        return false;
+    }
+    return --(*rc) == 0;
+}
+
+static void
+print(unsigned indent, FILE *out, struct apfl_value value)
+{
+    switch (value.type) {
+    case APFL_VALUE_NIL:
+        apfl_print_indented(indent, out, "nil\n");
+        return;
+    case APFL_VALUE_BOOLEAN:
+        apfl_print_indented(indent, out, value.boolean ? "true\n" : "false\n");
+        return;
+    case APFL_VALUE_NUMBER:
+        apfl_print_indented(indent, out, "%f\n", value.number);
+        return;
+    case APFL_VALUE_STRING:
+        apfl_print_indented(indent, out, "\"" APFL_STR_FMT "\"\n", APFL_STR_FMT_ARGS(value.string));
+        return;
+    case APFL_VALUE_LIST:
+        apfl_print_indented(indent, out, "[\n");
+        for (size_t i = 0; i < value.list->len; i++) {
+            print(indent+1, out, value.list->items[i]);
+        }
+        apfl_print_indented(indent, out, "]\n");
+        return;
+    }
+
+    fprintf(out, "Unknown value? (%d)\n", (int)value.type);
+}
+
+bool
+apfl_value_copy(struct apfl_value *dst, struct apfl_value src)
+{
+    struct apfl_string string;
+
+    *dst = src;
+
+    switch (src.type) {
+    case APFL_VALUE_NIL:
+    case APFL_VALUE_BOOLEAN:
+    case APFL_VALUE_NUMBER:
+        // Nothing to do
+        goto ok;
+    case APFL_VALUE_STRING:
+        string = apfl_string_blank();
+        if (!apfl_string_copy(&string, apfl_string_view_from(src.string))) {
+            return false;
+        }
+        dst->string = string;
+        goto ok;
+    case APFL_VALUE_LIST:
+        assert(src.list != NULL);
+        assert(dst->list == src.list);
+        src.list->refcount++;
+        goto ok;
+    }
+
+    assert(false);
+
+ok:
+    return true;
+}
+
+void
+apfl_value_print(struct apfl_value value, FILE *out)
+{
+    print(0, out, value);
+}
+
+struct apfl_list *
+apfl_list_new(void)
+{
+    struct apfl_list *list = ALLOC(struct apfl_list);
+    if (list == NULL) {
+        return NULL;
+    }
+
+    *list = (struct apfl_list) {
+        .refcount = 1,
+        .items = NULL,
+        .len = 0,
+        .cap = 0,
+    };
+
+    return list;
+}
+
+void
+apfl_list_deinit(struct apfl_list *list)
+{
+    DEINIT_LIST(list->items, list->len, apfl_value_deinit);
+    list->refcount = 0;
+    list->cap = 0;
+}
+
+void
+apfl_value_deinit(struct apfl_value *value)
+{
+    switch (value->type) {
+    case APFL_VALUE_NIL:
+    case APFL_VALUE_BOOLEAN:
+    case APFL_VALUE_NUMBER:
+        goto ok;
+    case APFL_VALUE_STRING:
+        apfl_string_deinit(&value->string);
+        goto ok;
+    case APFL_VALUE_LIST:
+        if (dec_refcount(&value->list->refcount)) {
+            DESTROY(value->list, apfl_list_deinit);
+        }
+        goto ok;
+    }
+
+    assert(false);
+
+ok:
+    value->type = APFL_VALUE_NIL;
+}
diff --git a/src/value.h b/src/value.h
deleted file mode 100644
index e69de29..0000000