diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4372b92..8fe7bdd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,7 +8,14 @@ project(libabacus)
 
 add_compile_options(-pedantic -Wall)
 
+add_library(abacus STATIC src/lexer.c)
 add_executable(libabacus src/main.c)
+add_subdirectory(external/liblex)
 
+set_property(TARGET abacus PROPERTY C_STANDARD 90)
 set_property(TARGET libabacus PROPERTY C_STANDARD 90)
+target_include_directories(abacus PUBLIC include)
 target_include_directories(libabacus PUBLIC include)
+
+target_link_libraries(abacus lex)
+target_link_libraries(libabacus abacus)
diff --git a/include/lexer.h b/include/lexer.h
new file mode 100644
index 0000000..f816ce7
--- /dev/null
+++ b/include/lexer.h
@@ -0,0 +1,37 @@
+#ifndef LIBABACUS_LEXER_H
+#define LIBABACUS_LEXER_H
+
+#include "eval.h"
+#include "libabacus.h"
+
+/**
+ * The lexer used for reading
+ * a string and converting it into
+ * tokens.
+ */
+struct lexer {
+    /**
+     * The liblex configuration used
+     * to convert the string into tokens.
+     */
+    eval_config config;
+};
+
+typedef struct lexer lexer;
+
+/**
+ * Initializes the given lexer,
+ * placing the default tokens into it.
+ * @param lexer the lexer to intiailize.
+ * @return the result of the operation (can be MALLOC on failed allocation.)
+ */
+libab_result lexer_init(lexer* lexer);
+/**
+ * Releases the memory associated with the given lexer,
+ * removing all registered patterns from it.
+ * @param lexer the lexer to free.
+ * @return the result of the operation.
+ */
+libab_result lexer_free(lexer* lexer);
+
+#endif
diff --git a/include/libabacus.h b/include/libabacus.h
new file mode 100644
index 0000000..e74312d
--- /dev/null
+++ b/include/libabacus.h
@@ -0,0 +1,15 @@
+#ifndef LIBABACUS_H
+#define LIBABACUS_H
+
+/**
+ * An enum that represents the outcomes of
+ * libabacus functions that can fail.
+ */
+enum libab_result {
+    LIBAB_SUCCESS,
+    LIBAB_MALLOC
+};
+
+typedef enum libab_result libab_result;
+
+#endif
diff --git a/src/lexer.c b/src/lexer.c
new file mode 100644
index 0000000..723ab1d
--- /dev/null
+++ b/src/lexer.c
@@ -0,0 +1 @@
+#include "lexer.h"