Add header files for all modules

20 files changed, 445 insertions, 235 deletions

diff --git a/src/bootstrap/environment.c b/src/bootstrap/environment.c
index d5e954b..3fe8be1 100644
--- a/src/bootstrap/environment.c
+++ b/src/bootstrap/environment.c
@@ -1,21 +1,6 @@
-typedef struct EnvEntry {
-    Object *symbol;
-    Object *value;
-} EnvEntry;
-
-typedef struct Environment {
-    struct Environment *parent;
-    EnvEntry *buf;
-    size_t size;
-    size_t cap;
-    bool marked;
-} Environment;
-
-static Environment *global_env;
-
-#define ENV_BUF_CAP 8
-
-Environment *alloc_env(void);
+#include "environment.h"
+#include "gc.h"
+#include "errors.h"
 
 Environment *
 env_create(Environment *parent) {
diff --git a/src/bootstrap/environment.h b/src/bootstrap/environment.h
new file mode 100644
index 0000000..cc13921
--- /dev/null
+++ b/src/bootstrap/environment.h
@@ -0,0 +1,34 @@
+#ifndef BDL_ENVIRONMENT_H
+#define BDL_ENVIRONMENT_H
+
+#include "objects.h"
+
+typedef struct EnvEntry {
+    Object *symbol;
+    Object *value;
+} EnvEntry;
+
+typedef struct Environment {
+    struct Environment *parent;
+    EnvEntry *buf;
+    size_t size;
+    size_t cap;
+    bool marked;
+} Environment;
+
+Environment * env_create(Environment *parent);
+void env_add_symbol(Environment *env, Object *symbol, Object *value);
+Object * env_lookup(Environment *env, Object *symbol);
+Object * env_update(Environment *env, Object *symbol, Object *value);
+ssize_t env_index_current(Environment *env, Object *symbol);
+void env_add_or_update_current(Environment *env, Object *symbol, Object *value);
+Environment * env_extend(Environment *parent, Environment *extra);
+
+#define MAKE_ENV_VAR(ENV,STR,VAR) \
+    (env_add_symbol((ENV), MAKE_SYM(STR), (VAR)))
+#define MAKE_ENV_PROC(ENV,STR,FUN) \
+    (env_add_symbol((ENV), MAKE_SYM(STR), make_procedure(FUN)))
+
+#define ENV_BUF_CAP 8
+
+#endif // BDL_ENVIRONMENT_H
diff --git a/src/bootstrap/errors.c b/src/bootstrap/errors.c
index c1d2879..d957cfa 100644
--- a/src/bootstrap/errors.c
+++ b/src/bootstrap/errors.c
@@ -1,32 +1,4 @@
-typedef enum ErrorType {
-    ERR_TYPE_LEXER,
-    ERR_TYPE_PARSER,
-    ERR_TYPE_RUNTIME,
-} ErrorType;
-
-typedef enum ErrorValue {
-    ERR_UNKNOWN = 0,
-    ERR_UNMATCHED_STRING,
-    ERR_UNBALANCED_PAREN,
-    ERR_NOT_IMPLEMENTED,
-    ERR_EOF_REACHED,
-    ERR_UNKNOWN_TOKEN,
-    ERR_UNKNOWN_OBJ_TYPE,
-    ERR_NOT_A_SYMBOL,
-    ERR_SYMBOL_NOT_FOUND,
-    ERR_OBJ_NOT_CALLABLE,
-    ERR_NOT_ENOUGH_ARGS,
-    ERR_TOO_MANY_ARGS,
-    ERR_WRONG_ARG_TYPE,
-    ERR_DIVISION_BY_ZERO,
-} ErrorValue;
-
-typedef struct Error {
-    ErrorType type;
-    ErrorValue value;
-    size_t line;
-    size_t col;
-} Error;
+#include "errors.h"
 
 static const char* error_msgs[] = {
     [ERR_UNKNOWN] = "error: something unexpected happened",
@@ -45,7 +17,6 @@ static const char* error_msgs[] = {
     [ERR_DIVISION_BY_ZERO] = "error: division by zero",
 };
 
-#define ERR_MAX_NUMBER 16
 static Error errors[ERR_MAX_NUMBER];
 static size_t errors_n = 0;
 static bool supress_errors = false;
diff --git a/src/bootstrap/errors.h b/src/bootstrap/errors.h
new file mode 100644
index 0000000..7916f4a
--- /dev/null
+++ b/src/bootstrap/errors.h
@@ -0,0 +1,38 @@
+#ifndef BDL_ERRORS_H
+#define BDL_ERRORS_H
+
+typedef enum ErrorType {
+    ERR_TYPE_LEXER,
+    ERR_TYPE_PARSER,
+    ERR_TYPE_RUNTIME,
+} ErrorType;
+
+typedef enum ErrorValue {
+    ERR_UNKNOWN = 0,
+    ERR_UNMATCHED_STRING,
+    ERR_UNBALANCED_PAREN,
+    ERR_NOT_IMPLEMENTED,
+    ERR_EOF_REACHED,
+    ERR_UNKNOWN_TOKEN,
+    ERR_UNKNOWN_OBJ_TYPE,
+    ERR_NOT_A_SYMBOL,
+    ERR_SYMBOL_NOT_FOUND,
+    ERR_OBJ_NOT_CALLABLE,
+    ERR_NOT_ENOUGH_ARGS,
+    ERR_TOO_MANY_ARGS,
+    ERR_WRONG_ARG_TYPE,
+    ERR_DIVISION_BY_ZERO,
+} ErrorValue;
+
+typedef struct Error {
+    ErrorType type;
+    ErrorValue value;
+    size_t line;
+    size_t col;
+} Error;
+
+void error_push(Error error);
+
+#define ERR_MAX_NUMBER 16
+
+#endif // BDL_ERRORS_H
diff --git a/src/bootstrap/gc.c b/src/bootstrap/gc.c
index 11a1f5a..473930a 100644
--- a/src/bootstrap/gc.c
+++ b/src/bootstrap/gc.c
@@ -1,48 +1,4 @@
-// Stack of root nodes.
-typedef struct RootNodes {
-    Object **buf;
-    size_t size;
-    size_t cap;
-} RootNodes;
-
-// Stack of active environments.
-typedef struct ActiveEnvs {
-    Environment **buf;
-    size_t size;
-    size_t cap;
-} ActiveEnvs;
-
-typedef struct Environments {
-    Environment *buf;
-    size_t size;
-    size_t cap;
-} Environments;
-
-typedef struct FreeList {
-    size_t *buf;
-    size_t size;
-    size_t cap;
-    size_t position;
-} FreeList;
-
-typedef struct GC {
-    RootNodes roots;
-    Environments envs;
-    Object *objects;
-    size_t obj_cap;
-    FreeList free_objects;
-    FreeList free_envs;
-    ActiveEnvs active_envs;
-} GC;
-
-#define GC_OBJS_CAP  1024 * 1024
-#define GC_ROOTS_CAP 1024
-#define GC_ENVS_CAP  1024 * 4
-
-static GC gc;
-
-void mark_and_sweep(void);
-void dump_gc(void);
+#include "gc.h"
 
 Environment *
 alloc_env(void) {
@@ -115,9 +71,9 @@ init_gc(void) {
             .cap = GC_ENVS_CAP,
         },
         .active_envs = (ActiveEnvs){
-            .buf = malloc(GC_ROOTS_CAP * sizeof(Environment*)),
+            .buf = malloc(GC_ACTIVE_ENVS_CAP * sizeof(Environment*)),
             .size = 0,
-            .cap = GC_ROOTS_CAP,
+            .cap = GC_ACTIVE_ENVS_CAP,
         },
     };
 
@@ -131,13 +87,6 @@ init_gc(void) {
     }
 }
 
-Object *
-get_obj(size_t offset) {
-    return &gc.objects[offset];
-}
-
-void mark_obj(Object *obj);
-
 void
 mark_environment(Environment *env) {
     if (env == NULL || env->marked) {
@@ -190,11 +139,15 @@ mark_and_sweep(void) {
         if (!obj->marked) {
             // Free heap allocated memory for this object if needed.
             if (obj->type == OBJ_TYPE_SYMBOL) {
-                free(obj->symbol);
+                if (obj->symbol != NULL) {
+                    free(obj->symbol);
+                }
                 obj->symbol = NULL;
                 obj->symbol_n = 0;
             } else if (obj->type == OBJ_TYPE_STRING) {
-                free(obj->string);
+                if (obj->symbol != NULL) {
+                    free(obj->string);
+                }
                 obj->string = NULL;
                 obj->string_n = 0;
             }
@@ -280,7 +233,7 @@ alloc_object(ObjectType type) {
     }
     size_t slot = gc.free_objects.buf[gc.free_objects.position++];
     gc.free_objects.size--;
-    Object *obj = get_obj(slot);
+    Object *obj = &gc.objects[slot];
     obj->type = type;
     obj->marked = false;
     return obj;
diff --git a/src/bootstrap/gc.h b/src/bootstrap/gc.h
new file mode 100644
index 0000000..038c820
--- /dev/null
+++ b/src/bootstrap/gc.h
@@ -0,0 +1,69 @@
+#ifndef BDL_GC_H
+#define BDL_GC_H
+
+#include "objects.h"
+#include "environment.h"
+
+// Stack of root nodes.
+typedef struct RootNodes {
+    Object **buf;
+    size_t size;
+    size_t cap;
+} RootNodes;
+
+// Stack of active environments.
+typedef struct ActiveEnvs {
+    Environment **buf;
+    size_t size;
+    size_t cap;
+} ActiveEnvs;
+
+typedef struct Environments {
+    Environment *buf;
+    size_t size;
+    size_t cap;
+} Environments;
+
+typedef struct FreeList {
+    size_t *buf;
+    size_t size;
+    size_t cap;
+    size_t position;
+} FreeList;
+
+typedef struct GC {
+    RootNodes roots;
+    Environments envs;
+    Object *objects;
+    size_t obj_cap;
+    FreeList free_objects;
+    FreeList free_envs;
+    ActiveEnvs active_envs;
+} GC;
+
+void init_gc(void);
+
+// Allocation functions for objects and environments.
+Object * alloc_object(ObjectType type);
+Environment * alloc_env(void);
+
+// Root and environment protector functions.
+void push_root(Object *obj);
+Object * pop_root(void);
+void push_active_env(Environment *env);
+Environment * pop_active_env(void);
+
+// Mark and sweep algorithm functions.
+void mark_environment(Environment *env);
+void mark_obj(Object *obj);
+void mark_and_sweep(void);
+
+// Debugging function to print out the contentes of some GC fields.
+void dump_gc(void);
+
+#define GC_OBJS_CAP  1024 * 1024
+#define GC_ROOTS_CAP 1024
+#define GC_ACTIVE_ENVS_CAP 2
+#define GC_ENVS_CAP  1024 * 4
+
+#endif // BDL_GC_H
diff --git a/src/bootstrap/lexer.c b/src/bootstrap/lexer.c
index ee387dd..05324eb 100644
--- a/src/bootstrap/lexer.c
+++ b/src/bootstrap/lexer.c
@@ -1,29 +1,4 @@
-typedef enum TokenType {
-    TOKEN_UNKNOWN = 0,
-    TOKEN_LPAREN,
-    TOKEN_RPAREN,
-    TOKEN_QUOTE,
-    TOKEN_TRUE,
-    TOKEN_FALSE,
-    TOKEN_NIL,
-    TOKEN_FIXNUM,
-    TOKEN_SYMBOL,
-    TOKEN_STRING,
-    TOKEN_EOF,
-} TokenType;
-
-typedef struct Token {
-    TokenType type;
-    StringView value;
-    size_t line;
-    size_t column;
-} Token;
-
-typedef struct Tokens {
-    Token *buf;
-    size_t size;
-    size_t cap;
-} Tokens;
+#include "lexer.h"
 
 void
 print_token(Token tok) {
@@ -69,8 +44,6 @@ print_token(Token tok) {
     printf("\n");
 }
 
-#define TOK_BUF_CAP 256
-
 void
 push_token(Tokens *tokens, Token tok) {
     if (tokens->buf == NULL) {
@@ -84,13 +57,6 @@ push_token(Tokens *tokens, Token tok) {
     tokens->buf[tokens->size++] = tok;
 }
 
-typedef struct Scanner {
-    StringView current;
-    size_t line_number;
-    size_t col_number;
-    size_t offset;
-} Scanner;
-
 char
 scan_next(Scanner *scanner) {
     char c = sv_next(&scanner->current);
@@ -157,7 +123,7 @@ is_delimiter(char c) {
 }
 
 TokenType
-find_primitive_type(StringView value) {
+find_primitive_type(const StringView value) {
     bool is_fixnum = true;
     for (size_t i = 0; i < value.n; i++) {
         char c = value.start[i];
diff --git a/src/bootstrap/lexer.h b/src/bootstrap/lexer.h
new file mode 100644
index 0000000..129fd9a
--- /dev/null
+++ b/src/bootstrap/lexer.h
@@ -0,0 +1,66 @@
+#ifndef BDL_LEXER_H
+#define BDL_LEXER_H
+
+typedef enum TokenType {
+    TOKEN_UNKNOWN = 0,
+    TOKEN_LPAREN,
+    TOKEN_RPAREN,
+    TOKEN_QUOTE,
+    TOKEN_TRUE,
+    TOKEN_FALSE,
+    TOKEN_NIL,
+    TOKEN_FIXNUM,
+    TOKEN_SYMBOL,
+    TOKEN_STRING,
+    TOKEN_EOF,
+} TokenType;
+
+typedef struct Token {
+    TokenType type;
+    StringView value;
+    size_t line;
+    size_t column;
+} Token;
+
+typedef struct Tokens {
+    Token *buf;
+    size_t size;
+    size_t cap;
+} Tokens;
+
+typedef struct Scanner {
+    StringView current;
+    size_t line_number;
+    size_t col_number;
+    size_t offset;
+} Scanner;
+
+// Print a token to standard output for debugging purposes.
+void print_token(Token tok);
+
+// Push a token to the token list.
+void push_token(Tokens *tokens, Token tok);
+
+// Same functionality as the ScanView pairs, but keeping track of line and
+// column numbers.
+char scan_next(Scanner *scanner);
+char scan_peek(const Scanner *scanner);
+
+// Check if the current scanner still have characters left.
+bool scan_has_next(const Scanner *scanner);
+
+// Advance the scanner until we ran out of whitespace.
+void skip_whitespace(Scanner *scanner);
+
+// Check if a given character is a delimiter.
+bool is_delimiter(char c);
+
+// Extract the token type from the current string.
+TokenType find_primitive_type(const StringView value);
+
+// Generate a list of tokens from the given string.
+Tokens tokenize(const StringView *sv);
+
+#define TOK_BUF_CAP 256
+
+#endif // BDL_LEXER_H
diff --git a/src/bootstrap/main.c b/src/bootstrap/main.c
index 2d24f92..cfad9f1 100755
--- a/src/bootstrap/main.c
+++ b/src/bootstrap/main.c
@@ -6,25 +6,17 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "string_view.c"
-#include "read_line.c"
+#include "singletons.c"
+
+#include "environment.c"
 #include "errors.c"
+#include "gc.c"
 #include "lexer.c"
 #include "objects.c"
 #include "parser.c"
-#include "environment.c"
-#include "gc.c"
 #include "primitives.c"
-
-//
-// Utility macros.
-//
-
-#define MAKE_SYM(STR) make_symbol((StringView){(STR), sizeof(STR) - 1})
-#define MAKE_ENV_VAR(ENV,STR,VAR) \
-    (env_add_symbol((ENV), MAKE_SYM(STR), (VAR)))
-#define MAKE_ENV_PROC(ENV,STR,FUN) \
-    (env_add_symbol((ENV), MAKE_SYM(STR), make_procedure(FUN)))
+#include "read_line.c"
+#include "string_view.c"
 
 void
 init(void) {
@@ -113,7 +105,7 @@ process_source(const StringView *source) {
         .current = 0,
     };
     while (has_next_token(&visitor) && peek_token(&visitor).type != TOKEN_EOF) {
-        // check the stack before parsing
+        // Check the root node stack size before parsing
         size_t root_stack_size = gc.roots.size;
         Object *root = parse_tree(&visitor);
         gc.roots.size = root_stack_size;
diff --git a/src/bootstrap/objects.c b/src/bootstrap/objects.c
index 09076db..359329b 100644
--- a/src/bootstrap/objects.c
+++ b/src/bootstrap/objects.c
@@ -1,70 +1,10 @@
-typedef enum ObjectType {
-    OBJ_TYPE_FIXNUM,
-    OBJ_TYPE_BOOL,
-    OBJ_TYPE_NIL,
-    OBJ_TYPE_SYMBOL,
-    OBJ_TYPE_STRING,
-    OBJ_TYPE_PAIR,
-    OBJ_TYPE_PROCEDURE,
-    OBJ_TYPE_LAMBDA,
-    OBJ_TYPE_ERR,
-} ObjectType;
-
-struct Environment;
-
-typedef struct Object {
-    ObjectType type;
-    bool marked;
-    union {
-        // OBJ_TYPE_FIXNUM
-        ssize_t fixnum;
-
-        // OBJ_TYPE_STRING
-        struct {
-            char *string;
-            size_t string_n;
-        };
-
-        // OBJ_TYPE_PAIR
-        struct {
-            struct Object *car;
-            struct Object *cdr;
-        };
-
-        // OBJ_TYPE_SYMBOL
-        struct {
-            char *symbol;
-            size_t symbol_n;
-        };
-
-        // OBJ_TYPE_PROCEDURE
-        struct Object *(*proc)(struct Environment *env, struct Object *args);
-
-        // OBJ_TYPE_LAMBDA
-        struct {
-            struct Object *params;
-            struct Object *body;
-            struct Environment *env;
-        };
-    };
-} Object;
-
-//
-// Singletons.
-//
-
-static Object *obj_nil;
-static Object *obj_true;
-static Object *obj_false;
-static Object *obj_err;
-static Object *obj_quote;
+#include "gc.h"
+#include "objects.h"
 
 //
 // Constructors.
 //
 
-Object * alloc_object(ObjectType);
-
 Object *
 make_fixnum(ssize_t num) {
     Object *obj = alloc_object(OBJ_TYPE_FIXNUM);
@@ -116,8 +56,6 @@ append_string(Object *obj, const StringView sv) {
     obj->string_n += sv.n;
 }
 
-void display(Object *root);
-
 void
 display_pair(Object *root) {
     display(root->car);
diff --git a/src/bootstrap/objects.h b/src/bootstrap/objects.h
new file mode 100644
index 0000000..56821eb
--- /dev/null
+++ b/src/bootstrap/objects.h
@@ -0,0 +1,77 @@
+#ifndef BDL_OBJECTS_H
+#define BDL_OBJECTS_H
+
+#include "string_view.h"
+
+typedef enum ObjectType {
+    OBJ_TYPE_FIXNUM,
+    OBJ_TYPE_BOOL,
+    OBJ_TYPE_NIL,
+    OBJ_TYPE_SYMBOL,
+    OBJ_TYPE_STRING,
+    OBJ_TYPE_PAIR,
+    OBJ_TYPE_PROCEDURE,
+    OBJ_TYPE_LAMBDA,
+    OBJ_TYPE_ERR,
+} ObjectType;
+
+struct Environment;
+
+typedef struct Object {
+    ObjectType type;
+    bool marked;
+    union {
+        // OBJ_TYPE_FIXNUM
+        ssize_t fixnum;
+
+        // OBJ_TYPE_STRING
+        struct {
+            char *string;
+            size_t string_n;
+        };
+
+        // OBJ_TYPE_PAIR
+        struct {
+            struct Object *car;
+            struct Object *cdr;
+        };
+
+        // OBJ_TYPE_SYMBOL
+        struct {
+            char *symbol;
+            size_t symbol_n;
+        };
+
+        // OBJ_TYPE_PROCEDURE
+        struct Object *(*proc)(struct Environment *env, struct Object *args);
+
+        // OBJ_TYPE_LAMBDA
+        struct {
+            struct Object *params;
+            struct Object *body;
+            struct Environment *env;
+        };
+    };
+} Object;
+
+// Object constructors.
+Object * make_fixnum(ssize_t num);
+Object * make_procedure(Object *(*proc)(struct Environment *, struct Object *args));
+Object * make_pair(Object *car, Object *cdr);
+Object * make_symbol(StringView sv);
+Object * make_string(void);
+void append_string(Object *obj, const StringView sv);
+
+// Object representation.
+void display(Object *root);
+void display_pair(Object *root);
+
+// Object comparison.
+bool obj_eq(Object *a, Object* b);
+
+// Utility macros.
+#define DEBUG_OBJ(MSG,OBJ) printf((MSG)); display(OBJ); printf("\n");
+#define PRINT_OBJ(OBJ) display(OBJ); printf("\n");
+#define MAKE_SYM(STR) make_symbol((StringView){(STR), sizeof(STR) - 1})
+
+#endif // BDL_OBJECTS_H
diff --git a/src/bootstrap/parser.c b/src/bootstrap/parser.c
index 77ece9d..5b0033a 100644
--- a/src/bootstrap/parser.c
+++ b/src/bootstrap/parser.c
@@ -1,7 +1,4 @@
-typedef struct Visitor {
-    Tokens tokens;
-    size_t current;
-} Visitor;
+#include "parser.h"
 
 Token
 peek_token(const Visitor *visitor) {
@@ -18,8 +15,6 @@ has_next_token(const Visitor *visitor) {
     return visitor->current < visitor->tokens.size;
 }
 
-void push_root(Object*);
-
 Object *
 parse_fixnum(Token tok) {
     ssize_t num = 0;
@@ -38,8 +33,6 @@ parse_fixnum(Token tok) {
     return obj;
 }
 
-Object * parse_tree(Visitor *vs);
-
 Object *
 parse_list(Visitor *vs) {
     Token tok = peek_token(vs);
diff --git a/src/bootstrap/parser.h b/src/bootstrap/parser.h
new file mode 100644
index 0000000..3bd17ef
--- /dev/null
+++ b/src/bootstrap/parser.h
@@ -0,0 +1,22 @@
+#ifndef BDL_PARSER_H
+#define BDL_PARSER_H
+
+typedef struct Visitor {
+    Tokens tokens;
+    size_t current;
+} Visitor;
+
+// Mimics the functionality in the Scanner functions, but for entire tokens.
+Token next_token(Visitor *visitor);
+Token peek_token(const Visitor *visitor);
+bool has_next_token(const Visitor *visitor);
+
+// Parse a token into a fixnum object.
+Object * parse_fixnum(Token tok);
+
+// Recursive descent parser. If an object is not a list the parsing is handled
+// by the parse_tree function.
+Object * parse_list(Visitor *vs);
+Object * parse_tree(Visitor *vs);
+
+#endif // BDL_PARSER_H
diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index 0c2a17d..0f1498d 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -1,5 +1,4 @@
-#define DEBUG_OBJ(MSG,OBJ) printf((MSG)); display(OBJ); printf("\n");
-static Object *proc_if;
+#include "primitives.h"
 
 Object *
 eval(Environment *env, Object *root) {
@@ -153,6 +152,7 @@ eval_lambda:
         .value = ERR_UNKNOWN_OBJ_TYPE,
     });
     return obj_err;
+
 eval_success:
     if (recursion_active) {
         // Remove stack protector.
diff --git a/src/bootstrap/primitives.h b/src/bootstrap/primitives.h
new file mode 100644
index 0000000..f874b17
--- /dev/null
+++ b/src/bootstrap/primitives.h
@@ -0,0 +1,60 @@
+#ifndef BDL_PRIMITIVES_H
+#define BDL_PRIMITIVES_H
+
+// Function evaluation.
+Object * eval(Environment *env, Object *root);
+
+// Evaluation functions.
+Object * proc_quote(Environment *env, Object *obj);
+Object * proc_eval(Environment *env, Object *obj);
+
+// Arithmetic.
+Object * proc_sum(Environment *env, Object *obj);
+Object * proc_sub(Environment *env, Object *obj);
+Object * proc_mul(Environment *env, Object *obj);
+Object * proc_div(Environment *env, Object *obj);
+Object * proc_mod(Environment *env, Object *obj);
+
+// Printing.
+Object * proc_display(Environment *env, Object *obj);
+Object * proc_print(Environment *env, Object *obj);
+Object * proc_newline(Environment *env, Object *obj);
+
+// Type checking.
+Object * proc_is_boolean(Environment *env, Object *obj);
+Object * proc_is_nil(Environment *env, Object *obj);
+Object * proc_is_symbol(Environment *env, Object *obj);
+Object * proc_is_string(Environment *env, Object *obj);
+Object * proc_is_fixnum(Environment *env, Object *obj);
+Object * proc_is_pair(Environment *env, Object *obj);
+Object * proc_is_procedure(Environment *env, Object *obj);
+Object * proc_is_error(Environment *env, Object *obj);
+
+// Logical operations.
+Object * proc_not(Environment *env, Object *obj);
+Object * proc_and(Environment *env, Object *obj);
+Object * proc_or(Environment *env, Object *obj);
+Object * proc_cond(Environment *env, Object *obj);
+Object * proc_num_less_than(Environment *env, Object *obj);
+Object * proc_num_greater_than(Environment *env, Object *obj);
+Object * proc_num_lesseq_than(Environment *env, Object *obj);
+Object * proc_num_greatereq_than(Environment *env, Object *obj);
+Object * proc_num_equal(Environment *env, Object *obj);
+Object * proc_equal(Environment *env, Object *obj);
+
+// List operations.
+Object * proc_car(Environment *env, Object *obj);
+Object * proc_cdr(Environment *env, Object *obj);
+Object * proc_cons(Environment *env, Object *obj);
+Object * proc_list(Environment *env, Object *obj);
+
+// Environment/variable manipulation.
+Object * proc_define(Environment *env, Object *obj);
+Object * proc_set(Environment *env, Object *obj);
+Object * proc_lambda(Environment *env, Object *obj);
+Object * proc_fun(Environment *env, Object *obj);
+
+// Runtinme configuration.
+Object * proc_supress_errors(Environment *env, Object *obj);
+
+#endif // BDL_PRIMITIVES_H
diff --git a/src/bootstrap/read_line.c b/src/bootstrap/read_line.c
index 603bfee..03146ad 100644
--- a/src/bootstrap/read_line.c
+++ b/src/bootstrap/read_line.c
@@ -1,4 +1,5 @@
-#define RL_BUF_SIZE 1024
+#include "read_line.h"
+
 static char readline_buf[RL_BUF_SIZE];
 
 StringView
diff --git a/src/bootstrap/read_line.h b/src/bootstrap/read_line.h
new file mode 100644
index 0000000..160bce0
--- /dev/null
+++ b/src/bootstrap/read_line.h
@@ -0,0 +1,10 @@
+#ifndef BDL_READ_LINE_H
+#define BDL_READ_LINE_H
+
+#include "string_view.h"
+
+StringView read_line(void);
+
+#define RL_BUF_SIZE 1024
+
+#endif // BDL_READ_LINE_H
diff --git a/src/bootstrap/singletons.c b/src/bootstrap/singletons.c
new file mode 100644
index 0000000..eb9c397
--- /dev/null
+++ b/src/bootstrap/singletons.c
@@ -0,0 +1,17 @@
+#include "environment.h"
+#include "gc.h"
+#include "objects.h"
+
+// Global garbage collector singleton.
+static GC gc;
+
+// Special singleton Objects.
+static Object *obj_nil;
+static Object *obj_true;
+static Object *obj_false;
+static Object *obj_err;
+static Object *obj_quote;
+static Object *proc_if;
+
+// Global environment.
+static Environment *global_env;
diff --git a/src/bootstrap/string_view.c b/src/bootstrap/string_view.c
index 13ba9e0..39fabe9 100644
--- a/src/bootstrap/string_view.c
+++ b/src/bootstrap/string_view.c
@@ -1,7 +1,4 @@
-typedef struct StringView {
-    char *start;
-    size_t n;
-} StringView;
+#include "string_view.h"
 
 char
 sv_next(StringView *sv) {
diff --git a/src/bootstrap/string_view.h b/src/bootstrap/string_view.h
new file mode 100644
index 0000000..42273ab
--- /dev/null
+++ b/src/bootstrap/string_view.h
@@ -0,0 +1,21 @@
+#ifndef BDL_STRINGVIEW_H
+#define BDL_STRINGVIEW_H
+
+typedef struct StringView {
+    char *start;
+    size_t n;
+} StringView;
+
+// Consume a character in the stream.
+char sv_next(StringView *sv);
+
+// Check what is the current character in the stream.
+char sv_peek(const StringView *sv);
+
+// Compare if the arguments are the same.
+bool sv_equal(const StringView *a, const StringView *b);
+
+// Write a character to the given output stream.
+void sv_write(const StringView *sv, FILE *file);
+
+#endif // BDL_STRINGVIEW_H