Create demo application

CMakeLists.txt

@@ -3,6 +3,7 @@ cmake_minimum_required(VERSION 3.15)
 project(imp LANGUAGES C)
 
 option(TESTS "Build tests" ON)
+option(DEMO "Build demo" ON)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
@@ -23,3 +24,7 @@ if (${TESTS})
   add_subdirectory(dep/unity)
   add_subdirectory(tests)
 endif()
+
+if (${DEMO})
+  add_subdirectory(demo)
+endif()

demo/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_executable(repl
+  main.c
+)
+configure_target(repl)
+target_link_libraries(repl PRIVATE imp)

demo/main.c

@@ -0,0 +1,9 @@
+#include "repl.h"
+
+static repl_t repl;
+
+int main(void)
+{
+	repl_init(&repl);
+	return repl_run(&repl);
+}

lib/CMakeLists.txt

@@ -1,8 +1,14 @@
 add_library(imp
   am.c
   env.c
+  eval.c
+  expr.c
   memory_stream.c
   parse.c
+  prim.c
+  print.c
+  read.c
+  repl.c
   store.c
   token.c
 )

lib/am.c

@@ -1,5 +1,8 @@
 #include "am.h"
 
+#include "env.h"
+#include "store.h"
+
 #include <assert.h>
 #include <string.h>
 
@@ -7,6 +10,8 @@ void am_init(am_t *am)
 {
 	memset(am, 0, sizeof(am_t));
 	am->sp = am->stack + AM_STACK_SIZE - 1;
+	store_init(am);
+	env_init(am);
 }
 
 void am_push(am_t *am)

lib/env.c

@@ -1,5 +1,7 @@
 #include "env.h"
 
+#include "prim.h"
+
 #include <assert.h>
 #include <string.h>
 
@@ -47,11 +49,10 @@ static expr_t **lookup(am_t *am, bool *found)
 	return &prev->pair.cdr;
 }
 
-void env_init(am_t *am, store_t *store)
+void env_init(am_t *am)
 {
-	am->env = store_alloc(store);
+	am->env = expr_empty_list(am);
-	am->env->is_atom = true;
+	prim_load(am);
-	am->env->atom.type = ATOM_TYPE_EMPTY_LIST;
 }
 
 void env_fetch(am_t *am)
@@ -61,7 +62,7 @@ void env_fetch(am_t *am)
 	am->val = found ? val : NULL;
 }
 
-void env_set(am_t *am, store_t *store)
+void env_set(am_t *am)
 {
 	bool found;
 	expr_t **loc = lookup(am, &found);
@@ -69,12 +70,7 @@ void env_set(am_t *am, store_t *store)
 		*loc = am->val;
 	} else {
 		(*loc)->is_atom = false;
-		(*loc)->pair.cdr = store_alloc(store);
+		(*loc)->pair.cdr = expr_empty_list(am);
-		(*loc)->pair.cdr->is_atom = true;
+		(*loc)->pair.car = expr_pair(am, am->expr, am->val);
-		(*loc)->pair.cdr->atom.type = ATOM_TYPE_EMPTY_LIST;
-
-		expr_t *entry = (*loc)->pair.car = store_alloc(store);
-		entry->pair.car = am->expr;
-		entry->pair.cdr = am->val;
 	}
 }

lib/eval.c

@@ -0,0 +1,42 @@
+#include "eval.h"
+
+#include "env.h"
+
+#include <assert.h>
+
+static void eval_atom(am_t *am)
+{
+	switch (am->expr->atom.type) {
+	case ATOM_TYPE_EMPTY_LIST:
+	case ATOM_TYPE_INTEGER:
+	case ATOM_TYPE_PRIM_PROC:
+		am->val = am->expr;
+		break;
+	case ATOM_TYPE_SYMBOL:
+		env_fetch(am);
+		break;
+	}
+}
+
+static void eval_list(am_t *am)
+{
+	am->argl = am->expr->pair.cdr;
+	am->expr = am->expr->pair.car;
+
+	assert(am->expr->is_atom);
+	assert(am->expr->atom.type == ATOM_TYPE_SYMBOL);
+	env_fetch(am);
+
+	assert(am->val->is_atom);
+	assert(am->val->atom.type == ATOM_TYPE_PRIM_PROC);
+	assert(am->val->atom.prim_proc != NULL);
+	am->val->atom.prim_proc(am);
+}
+
+void eval(am_t *am)
+{
+	if (am->expr->is_atom)
+		eval_atom(am);
+	else
+		eval_list(am);
+}

lib/expr.c

@@ -0,0 +1,56 @@
+#include "expr.h"
+
+#include "am.h"
+
+#include <string.h>
+
+expr_t *expr_integer(am_t *am, int64_t value)
+{
+	expr_t *expr = store_alloc(am);
+	expr->is_atom = true;
+	expr->atom.type = ATOM_TYPE_INTEGER;
+	expr->atom.integer = value;
+	return expr;
+}
+
+expr_t *expr_symbol(am_t *am, const symbol_t *symbol)
+{
+	expr_t *expr = store_alloc(am);
+	expr->is_atom = true;
+	expr->atom.type = ATOM_TYPE_SYMBOL;
+	memcpy(&expr->atom.symbol, symbol, sizeof(symbol_t));
+	return expr;
+}
+
+expr_t *expr_str_symbol(am_t *am, const char *str)
+{
+	symbol_t symbol = { .len = strlen(str) };
+	memcpy(symbol.buf, str, symbol.len);
+	return expr_symbol(am, &symbol);
+}
+
+expr_t *expr_empty_list(am_t *am)
+{
+	expr_t *expr = store_alloc(am);
+	expr->is_atom = true;
+	expr->atom.type = ATOM_TYPE_EMPTY_LIST;
+	return expr;
+}
+
+expr_t *expr_pair(am_t *am, expr_t *car, expr_t *cdr)
+{
+	expr_t *expr = store_alloc(am);
+	expr->is_atom = false;
+	expr->pair.car = car;
+	expr->pair.cdr = cdr;
+	return expr;
+}
+
+expr_t *expr_prim_proc(am_t *am, prim_proc_t prim_proc)
+{
+	expr_t *expr = store_alloc(am);
+	expr->is_atom = true;
+	expr->atom.type = ATOM_TYPE_PRIM_PROC;
+	expr->atom.prim_proc = prim_proc;
+	return expr;
+}

lib/include/am.h

@@ -2,12 +2,14 @@
 #define AM_H
 
 #include "expr.h"
+#include "store.h"
 
 #define AM_STACK_SIZE 128U
 
-typedef struct {
+typedef struct am {
-	expr_t *env, *expr, *val;
+	expr_t *argl, *env, *expr, *val;
 	expr_t **sp, *stack[AM_STACK_SIZE];
+	store_t store;
 } am_t;
 
 void am_init(am_t *am);

lib/include/env.h

@@ -2,10 +2,9 @@
 #define ENV_H
 
 #include "am.h"
-#include "store.h"
 
-void env_init(am_t *am, store_t *store);
+void env_init(am_t *am);
 void env_fetch(am_t *am);
-void env_set(am_t *am, store_t *store);
+void env_set(am_t *am);
 
 #endif

lib/include/eval.h

@@ -0,0 +1,8 @@
+#ifndef EVAL_H
+#define EVAL_H
+
+#include "am.h"
+
+void eval(am_t *am);
+
+#endif

lib/include/expr.h

@@ -7,15 +7,20 @@
 #include <stddef.h>
 #include <stdint.h>
 
+struct am;
+
 typedef struct {
 	char buf[MAX_SYMBOL_LEN];
 	size_t len;
 } symbol_t;
 
+typedef void (*prim_proc_t)(struct am *am);
+
 typedef enum {
 	ATOM_TYPE_EMPTY_LIST,
 	ATOM_TYPE_INTEGER,
 	ATOM_TYPE_SYMBOL,
+	ATOM_TYPE_PRIM_PROC,
 } atom_type_t;
 
 typedef struct {
@@ -23,6 +28,7 @@ typedef struct {
 	union {
 		int64_t integer;
 		symbol_t symbol;
+		prim_proc_t prim_proc;
 	};
 } atom_t;
 
@@ -40,4 +46,11 @@ typedef struct expr {
 	};
 } expr_t;
 
+expr_t *expr_integer(struct am *am, int64_t value);
+expr_t *expr_symbol(struct am *am, const symbol_t *symbol);
+expr_t *expr_str_symbol(struct am *am, const char *str);
+expr_t *expr_empty_list(struct am *am);
+expr_t *expr_pair(struct am *am, expr_t *car, expr_t *cdr);
+expr_t *expr_prim_proc(struct am *am, prim_proc_t prim_proc);
+
 #endif

lib/include/parse.h

@@ -2,7 +2,6 @@
 #define PARSE_H
 
 #include "am.h"
-#include "store.h"
 #include "token.h"
 
 #define PARSE_MAX_DEPTH 128U
@@ -21,7 +20,7 @@ typedef struct {
 	parse_state_t *sp, stack[PARSE_MAX_DEPTH];
 } parse_ctx_t;
 
-void parse_init(am_t *am, store_t *store, parse_ctx_t *out);
+void parse_init(am_t *am, parse_ctx_t *out);
 parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token);
 
 #endif

lib/include/prim.h

@@ -0,0 +1,9 @@
+#ifndef PRIM_H
+#define PRIM_H
+
+#include "am.h"
+#include "expr.h"
+
+void prim_load(am_t *am);
+
+#endif

lib/include/print.h

@@ -0,0 +1,8 @@
+#ifndef PRINT_H
+#define PRINT_H
+
+#include "am.h"
+
+size_t print(am_t *am, char *buffer, size_t buffer_size);
+
+#endif

lib/include/read.h

@@ -0,0 +1,9 @@
+#ifndef READ_H
+#define READ_H
+
+#include "am.h"
+#include "stream.h"
+
+void read(am_t *am, stream_t *stream);
+
+#endif

lib/include/repl.h

@@ -0,0 +1,16 @@
+#ifndef REPL_H
+#define REPL_H
+
+#include "am.h"
+
+#define REPL_IO_BUFFER_SIZE 256U
+
+typedef struct {
+	am_t am;
+	char io_buffer[REPL_IO_BUFFER_SIZE];
+} repl_t;
+
+void repl_init(repl_t *repl);
+int repl_run(repl_t *repl);
+
+#endif

lib/include/store.h

@@ -5,12 +5,14 @@
 
 #define STORE_SIZE 256U
 
-typedef struct {
+typedef struct store {
 	expr_t *free;
 	expr_t buffer[STORE_SIZE];
 } store_t;
 
-void store_init(store_t *store);
+struct am;
-expr_t *store_alloc(store_t *store);
+
+void store_init(struct am *am);
+expr_t *store_alloc(struct am *am);
 
 #endif

lib/parse.c

@@ -3,10 +3,9 @@
 #include <assert.h>
 #include <string.h>
 
-void parse_init(am_t *am, store_t *store, parse_ctx_t *out)
+void parse_init(am_t *am, parse_ctx_t *out)
 {
 	out->am = am;
-	out->store = store;
 	out->state = PARSE_STATE_INIT;
 	out->sp = out->stack + PARSE_MAX_DEPTH - 1;
 }
@@ -23,33 +22,16 @@ static parse_state_t pop_state(parse_ctx_t *ctx)
 	return *++ctx->sp;
 }
 
-static void load_integer(parse_ctx_t *ctx, expr_t **expr, int64_t integer)
+static void append(parse_ctx_t *ctx, expr_t *expr)
 {
-	*expr = store_alloc(ctx->store);
+	expr_t *list = ctx->am->expr;
-	(*expr)->is_atom = true;
+	while (!list->is_atom)
-	(*expr)->atom.type = ATOM_TYPE_INTEGER;
+		list = list->pair.cdr;
-	(*expr)->atom.integer = integer;
+	assert(list->atom.type == ATOM_TYPE_EMPTY_LIST);
-}
 
-static void
+	list->is_atom = false;
-load_symbol(parse_ctx_t *ctx, expr_t **expr, const symbol_t *symbol)
+	list->pair.car = expr;
-{
+	list->pair.cdr = expr_empty_list(ctx->am);
-	*expr = store_alloc(ctx->store);
-	(*expr)->is_atom = true;
-	(*expr)->atom.type = ATOM_TYPE_SYMBOL;
-	memcpy(&(*expr)->atom.symbol, symbol, sizeof(symbol_t));
-}
-
-static expr_t **append(parse_ctx_t *ctx, expr_t *expr)
-{
-	while (!expr->is_atom)
-		expr = expr->pair.cdr;
-	assert(expr->atom.type == ATOM_TYPE_EMPTY_LIST);
-	expr->is_atom = false;
-	expr->pair.cdr = store_alloc(ctx->store);
-	expr->pair.cdr->is_atom = true;
-	expr->pair.cdr->atom.type = ATOM_TYPE_EMPTY_LIST;
-	return &expr->pair.car;
 }
 
 parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
@@ -58,18 +40,16 @@ parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 	case PARSE_STATE_INIT:
 		switch (token->type) {
 		case TOKEN_TYPE_INTEGER:
-			load_integer(ctx, &ctx->am->expr, token->integer);
+			ctx->am->expr = expr_integer(ctx->am, token->integer);
 			ctx->state = PARSE_STATE_DONE;
 			break;
 		case TOKEN_TYPE_SYMBOL:
-			load_symbol(ctx, &ctx->am->expr, &token->symbol);
+			ctx->am->expr = expr_symbol(ctx->am, &token->symbol);
 			ctx->state = PARSE_STATE_DONE;
 			break;
 		case TOKEN_TYPE_OPEN_PAREN:
 			push_state(ctx, PARSE_STATE_DONE);
-			ctx->am->expr = store_alloc(ctx->store);
+			ctx->am->expr = expr_empty_list(ctx->am);
-			ctx->am->expr->is_atom = true;
-			ctx->am->expr->atom.type = ATOM_TYPE_EMPTY_LIST;
 			ctx->state = PARSE_STATE_LIST;
 			break;
 		case TOKEN_TYPE_CLOSE_PAREN:
@@ -80,21 +60,16 @@ parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 
 	case PARSE_STATE_LIST:
 		switch (token->type) {
-			expr_t **end_car;
 		case TOKEN_TYPE_INTEGER:
-			end_car = append(ctx, ctx->am->expr);
+			append(ctx, expr_integer(ctx->am, token->integer));
-			load_integer(ctx, end_car, token->integer);
 			break;
 		case TOKEN_TYPE_SYMBOL:
-			end_car = append(ctx, ctx->am->expr);
+			append(ctx, expr_symbol(ctx->am, &token->symbol));
-			load_symbol(ctx, end_car, &token->symbol);
 			break;
 		case TOKEN_TYPE_OPEN_PAREN:
 			am_push(ctx->am);
 			push_state(ctx, PARSE_STATE_LIST);
-			ctx->am->expr = store_alloc(ctx->store);
+			ctx->am->expr = expr_empty_list(ctx->am);
-			ctx->am->expr->is_atom = true;
-			ctx->am->expr->atom.type = ATOM_TYPE_EMPTY_LIST;
 			ctx->state = PARSE_STATE_LIST;
 			break;
 		case TOKEN_TYPE_CLOSE_PAREN:
@@ -102,8 +77,7 @@ parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 			if (ctx->state == PARSE_STATE_LIST) {
 				expr_t *expr = ctx->am->expr;
 				am_pop(ctx->am);
-				end_car = append(ctx, ctx->am->expr);
+				append(ctx, expr);
-				*end_car = expr;
 			}
 			break;
 		}

lib/prim.c

@@ -0,0 +1,74 @@
+#include "prim.h"
+
+#include "env.h"
+
+#include <assert.h>
+
+#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
+
+typedef struct {
+	const char *name;
+	prim_proc_t prim_proc;
+} prim_table_entry_t;
+
+static void add(am_t *am)
+{
+	assert(am->argl);
+
+	int64_t total = 0;
+	for (expr_t *list = am->argl; !list->is_atom; list = list->pair.cdr) {
+		assert(list->pair.car->is_atom);
+		assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
+		total += list->pair.car->atom.integer;
+	}
+	am->val = expr_integer(am, total);
+}
+
+static void mul(am_t *am)
+{
+	assert(am->argl);
+
+	int64_t total = 1;
+	for (expr_t *list = am->argl; !list->is_atom; list = list->pair.cdr) {
+		assert(list->pair.car->is_atom);
+		assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
+		total *= list->pair.car->atom.integer;
+	}
+	am->val = expr_integer(am, total);
+}
+
+static void sub(am_t *am)
+{
+	assert(am->argl);
+	assert(!am->argl->is_atom);
+	assert(am->argl->pair.car->is_atom);
+	assert(am->argl->pair.car->atom.type == ATOM_TYPE_INTEGER);
+
+	int64_t total = am->argl->pair.car->atom.integer;
+	if (!am->argl->is_atom && am->argl->pair.cdr->is_atom) {
+		total *= -1;
+	} else {
+		for (expr_t *list = am->argl->pair.cdr; !list->is_atom;
+		     list = list->pair.cdr) {
+			assert(list->pair.car->is_atom);
+			assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
+			total -= list->pair.car->atom.integer;
+		}
+	}
+	am->val = expr_integer(am, total);
+}
+
+static const prim_table_entry_t prim_table[] = {
+	{ "+", add },
+	{ "*", mul },
+	{ "-", sub },
+};
+
+void prim_load(am_t *am)
+{
+	for (unsigned i = 0; i < NELEMS(prim_table); ++i) {
+		am->expr = expr_str_symbol(am, prim_table[i].name);
+		am->val = expr_prim_proc(am, prim_table[i].prim_proc);
+		env_set(am);
+	}
+}

lib/print.c

@@ -0,0 +1,26 @@
+#include "print.h"
+
+#include <assert.h>
+
+size_t print(am_t *am, char *buffer, size_t buffer_size)
+{
+	assert(am->val->is_atom);
+	assert(am->val->atom.type == ATOM_TYPE_INTEGER);
+
+	int64_t value = am->val->atom.integer;
+	int divisor = 10;
+	while (divisor <= value)
+		divisor *= 10;
+
+	size_t i = 0;
+	do {
+		divisor /= 10;
+		const int digit = value / divisor;
+		value = value % divisor;
+
+		assert(i < buffer_size);
+		buffer[i++] = '0' + (char)digit;
+	} while (divisor > 1);
+
+	return i;
+}

lib/read.c

@@ -0,0 +1,22 @@
+#include "read.h"
+
+#include "parse.h"
+#include "token.h"
+
+#include <assert.h>
+
+void read(am_t *am, stream_t *stream)
+{
+	parse_ctx_t ctx;
+	token_t token;
+
+	parse_init(am, &ctx);
+
+	while (ctx.state != PARSE_STATE_DONE) {
+		const token_status_t token_status = token_read(stream, &token);
+		assert(token_status == TOKEN_OK);
+
+		parse_proc(&ctx, &token);
+		assert(ctx.state != PARSE_STATE_ERROR);
+	}
+}

lib/repl.c

@@ -0,0 +1,58 @@
+#include "repl.h"
+
+#include "eval.h"
+#include "memory_stream.h"
+#include "print.h"
+#include "read.h"
+
+#include <assert.h>
+#include <stdio.h>
+
+#define PROMPT "> "
+
+static int read_line(char buffer[REPL_IO_BUFFER_SIZE])
+{
+	for (unsigned i = 0; i < REPL_IO_BUFFER_SIZE; ++i) {
+		const int c = getchar();
+		switch (c) {
+		case EOF:
+			return EOF;
+		case '\n':
+			return (int)i;
+		default:
+			buffer[i] = (char)c;
+			break;
+		}
+	}
+	assert(false);
+	return -2;
+}
+
+void repl_init(repl_t *repl)
+{
+	am_init(&repl->am);
+}
+
+int repl_run(repl_t *repl)
+{
+	int len;
+	memory_stream_t input;
+
+	while (true) {
+		fputs(PROMPT, stdout);
+
+		len = read_line(repl->io_buffer);
+		if (len < 0) {
+			fputc('\n', stdout);
+			return 0;
+		}
+		memory_stream_init(&input, (const uint8_t *)repl->io_buffer, len);
+		read(&repl->am, (stream_t *)&input);
+
+		eval(&repl->am);
+
+		len = print(&repl->am, repl->io_buffer, REPL_IO_BUFFER_SIZE - 1);
+		repl->io_buffer[len] = '\n';
+		fwrite(repl->io_buffer, 1, len + 1, stdout);
+	}
+}

lib/store.c

@@ -1,14 +1,16 @@
 #include "store.h"
 
+#include "am.h"
+
 #include <string.h>
 
-void store_init(store_t *store)
+void store_init(am_t *am)
 {
-	memset(store, 0, sizeof(store_t));
+	memset(&am->store, 0, sizeof(store_t));
-	store->free = store->buffer;
+	am->store.free = am->store.buffer;
 }
 
-expr_t *store_alloc(store_t *store)
+expr_t *store_alloc(am_t *am)
 {
-	return store->free++;
+	return am->store.free++;
 }

tests/CMakeLists.txt

@@ -11,7 +11,13 @@ endfunction()
 add_test_suites(
   am_tests.c
   env_tests.c
+  eval_tests.c
+  expr_tests.c
+  integration_tests.c
   parse_tests.c
+  prim_tests.c
+  print_tests.c
+  read_tests.c
   store_tests.c
   token_tests.c
 )

tests/env_tests.c

@@ -4,31 +4,10 @@
 #include <string.h>
 
 static am_t am;
-static store_t store;
-
-static expr_t *integer(int64_t value)
-{
-	expr_t *expr = store_alloc(&store);
-	expr->is_atom = true;
-	expr->atom.type = ATOM_TYPE_INTEGER;
-	expr->atom.integer = value;
-	return expr;
-}
-
-static expr_t *symbol(const char *s)
-{
-	expr_t *expr = store_alloc(&store);
-	expr->is_atom = true;
-	expr->atom.type = ATOM_TYPE_SYMBOL;
-	memcpy(expr->atom.symbol.buf, s, strlen(s));
-	return expr;
-}
 
 void setUp(void)
 {
 	am_init(&am);
-	store_init(&store);
-	env_init(&am, &store);
 }
 
 void tearDown(void)
@@ -37,11 +16,11 @@ void tearDown(void)
 
 static void test_set_foo_to_42_then_fetch(void)
 {
-	am.expr = symbol("foo");
+	am.expr = expr_str_symbol(&am, "foo");
-	am.val = integer(42);
+	am.val = expr_integer(&am, 42);
-	env_set(&am, &store);
+	env_set(&am);
 
-	am.expr = symbol("foo");
+	am.expr = expr_str_symbol(&am, "foo");
 	am.val = NULL;
 	env_fetch(&am);
 
@@ -53,13 +32,13 @@ static void test_set_foo_to_42_then_fetch(void)
 
 static void test_update_foo_from_123_to_456_then_fetch(void)
 {
-	am.expr = symbol("foo");
+	am.expr = expr_str_symbol(&am, "foo");
-	am.val = integer(123);
+	am.val = expr_integer(&am, 123);
-	env_set(&am, &store);
+	env_set(&am);
-	am.val = integer(456);
+	am.val = expr_integer(&am, 456);
-	env_set(&am, &store);
+	env_set(&am);
 
-	am.expr = symbol("foo");
+	am.expr = expr_str_symbol(&am, "foo");
 	am.val = NULL;
 	env_fetch(&am);
 

tests/eval_tests.c

@@ -0,0 +1,100 @@
+#include "am.h"
+#include "env.h"
+#include "eval.h"
+#include "unity.h"
+
+static am_t am;
+
+void test_prim_proc(am_t *am)
+{
+	(void)am;
+}
+
+void setUp(void)
+{
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_42_self_evals(void)
+{
+	am.expr = expr_integer(&am, 42);
+
+	eval(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(42, am.val->atom.integer);
+}
+
+static void test_empty_list_self_evals(void)
+{
+	am.expr = expr_empty_list(&am);
+
+	eval(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_EMPTY_LIST, am.val->atom.type);
+}
+
+static void test_prim_proc_self_evals(void)
+{
+	am.expr = expr_prim_proc(&am, test_prim_proc);
+
+	eval(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+	TEST_ASSERT_EQUAL(test_prim_proc, am.val->atom.prim_proc);
+}
+
+static void test_foo_evals_to_42_when_set_in_env(void)
+{
+	am.expr = expr_str_symbol(&am, "foo");
+	am.val = expr_integer(&am, 42);
+	env_set(&am);
+	am.val = NULL;
+
+	eval(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(42, am.val->atom.integer);
+}
+
+static void test_add_1_2_3_evals_to_6(void)
+{
+	am.expr = expr_pair(
+	    &am, expr_str_symbol(&am, "+"),
+	    expr_pair(
+	        &am, expr_integer(&am, 1),
+	        expr_pair(
+	            &am, expr_integer(&am, 2),
+	            expr_pair(
+	                &am, expr_integer(&am, 3), expr_empty_list(&am)))));
+
+	eval(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(6, am.val->atom.integer);
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_42_self_evals);
+	RUN_TEST(test_empty_list_self_evals);
+	RUN_TEST(test_prim_proc_self_evals);
+	RUN_TEST(test_foo_evals_to_42_when_set_in_env);
+	RUN_TEST(test_add_1_2_3_evals_to_6);
+	return UNITY_END();
+}

tests/expr_tests.c

@@ -0,0 +1,123 @@
+#include "am.h"
+#include "expr.h"
+#include "unity.h"
+
+static am_t am;
+
+void test_prim_proc(am_t *am)
+{
+	(void)am;
+}
+
+void setUp(void)
+{
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_expr_integer_123(void)
+{
+	expr_t *expr = expr_integer(&am, 123);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, expr->atom.type);
+	TEST_ASSERT_EQUAL(123, expr->atom.integer);
+}
+
+static void test_expr_integer_456(void)
+{
+	expr_t *expr = expr_integer(&am, 456);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, expr->atom.type);
+	TEST_ASSERT_EQUAL(456, expr->atom.integer);
+}
+
+static void test_expr_symbol_foo(void)
+{
+	const symbol_t symbol = { .buf = "foo", .len = 3 };
+	expr_t *expr = expr_symbol(&am, &symbol);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, expr->atom.type);
+	TEST_ASSERT_EQUAL(3, expr->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("foo", expr->atom.symbol.buf, 3);
+}
+
+static void test_expr_symbol_quux(void)
+{
+	const symbol_t symbol = { .buf = "quux", .len = 4 };
+	expr_t *expr = expr_symbol(&am, &symbol);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, expr->atom.type);
+	TEST_ASSERT_EQUAL(4, expr->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("quux", expr->atom.symbol.buf, 4);
+}
+
+static void test_expr_str_symbol_foo(void)
+{
+	expr_t *expr = expr_str_symbol(&am, "foo");
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, expr->atom.type);
+	TEST_ASSERT_EQUAL(3, expr->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("foo", expr->atom.symbol.buf, 3);
+}
+
+static void test_expr_str_symbol_quux(void)
+{
+	expr_t *expr = expr_str_symbol(&am, "quux");
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, expr->atom.type);
+	TEST_ASSERT_EQUAL(4, expr->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("quux", expr->atom.symbol.buf, 4);
+}
+
+static void test_expr_empty_list(void)
+{
+	expr_t *expr = expr_empty_list(&am);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_EMPTY_LIST, expr->atom.type);
+}
+
+static void test_expr_pair(void)
+{
+	expr_t *car = expr_integer(&am, 123);
+	expr_t *cdr = expr_integer(&am, 456);
+	expr_t *expr = expr_pair(&am, car, cdr);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_FALSE(expr->is_atom);
+	TEST_ASSERT_EQUAL(car, expr->pair.car);
+	TEST_ASSERT_EQUAL(cdr, expr->pair.cdr);
+}
+
+static void test_expr_prim_proc(void)
+{
+
+	expr_t *expr = expr_prim_proc(&am, test_prim_proc);
+	TEST_ASSERT_NOT_NULL(expr);
+	TEST_ASSERT_TRUE(expr->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, expr->atom.type);
+	TEST_ASSERT_EQUAL(test_prim_proc, expr->atom.prim_proc);
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_expr_integer_123);
+	RUN_TEST(test_expr_integer_456);
+	RUN_TEST(test_expr_symbol_foo);
+	RUN_TEST(test_expr_symbol_quux);
+	RUN_TEST(test_expr_str_symbol_foo);
+	RUN_TEST(test_expr_str_symbol_quux);
+	RUN_TEST(test_expr_empty_list);
+	RUN_TEST(test_expr_pair);
+	RUN_TEST(test_expr_prim_proc);
+	return UNITY_END();
+}

tests/integration_tests.c

@@ -0,0 +1,48 @@
+#include "eval.h"
+#include "memory_stream.h"
+#include "print.h"
+#include "read.h"
+#include "unity.h"
+
+#include <string.h>
+
+#define BUFFER_SIZE 256U
+
+static am_t am;
+static char buffer[BUFFER_SIZE];
+
+static const char *read_eval_print(const char *input)
+{
+	memory_stream_t stream;
+	memory_stream_init(&stream, (const uint8_t *)input, strlen(input));
+	read(&am, (stream_t *)&stream);
+
+	eval(&am);
+
+	memset(buffer, 0, sizeof(buffer));
+	print(&am, buffer, BUFFER_SIZE - 1);
+	return buffer;
+}
+
+void setUp(void)
+{
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_unnested_arithmetic(void)
+{
+	TEST_ASSERT_EQUAL_STRING("10", read_eval_print("(+ 1 2 3 4)"));
+	TEST_ASSERT_EQUAL_STRING("42", read_eval_print("(* 2 21)"));
+	TEST_ASSERT_EQUAL_STRING("64", read_eval_print("(- 100 36)"));
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_unnested_arithmetic);
+	return UNITY_END();
+}

tests/parse_tests.c

@@ -1,7 +1,6 @@
 #include "parse.h"
 #include "unity.h"
 
-static store_t store;
 static am_t am;
 static parse_ctx_t ctx;
 
@@ -9,9 +8,8 @@ static parse_ctx_t ctx;
 
 void setUp(void)
 {
-	store_init(&store);
 	am_init(&am);
-	parse_init(&am, &store, &ctx);
+	parse_init(&am, &ctx);
 }
 
 void tearDown(void)

tests/prim_tests.c

@@ -0,0 +1,140 @@
+#include "env.h"
+#include "prim.h"
+#include "unity.h"
+
+static am_t am;
+
+void setUp(void)
+{
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_add_empty_list_is_0(void)
+{
+	am.expr = expr_str_symbol(&am, "+");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_empty_list(&am);
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(0, am.val->atom.integer);
+}
+
+static void test_add_1_2_3_is_6(void)
+{
+	am.expr = expr_str_symbol(&am, "+");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_pair(
+	    &am, expr_integer(&am, 1),
+	    expr_pair(
+	        &am, expr_integer(&am, 2),
+	        expr_pair(&am, expr_integer(&am, 3), expr_empty_list(&am))));
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(6, am.val->atom.integer);
+}
+
+static void test_mul_empty_list_is_1(void)
+{
+	am.expr = expr_str_symbol(&am, "*");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_empty_list(&am);
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(1, am.val->atom.integer);
+}
+
+static void test_mul_2_3_4_is_24(void)
+{
+	am.expr = expr_str_symbol(&am, "*");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_pair(
+	    &am, expr_integer(&am, 2),
+	    expr_pair(
+	        &am, expr_integer(&am, 3),
+	        expr_pair(&am, expr_integer(&am, 4), expr_empty_list(&am))));
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(24, am.val->atom.integer);
+}
+
+static void test_sub_1_is_minus_1(void)
+{
+	am.expr = expr_str_symbol(&am, "-");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_pair(&am, expr_integer(&am, 1), expr_empty_list(&am));
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(-1, am.val->atom.integer);
+}
+
+static void test_sub_5_4_3_is_minus_2(void)
+{
+	am.expr = expr_str_symbol(&am, "-");
+	env_fetch(&am);
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_PRIM_PROC, am.val->atom.type);
+
+	am.argl = expr_pair(
+	    &am, expr_integer(&am, 5),
+	    expr_pair(
+	        &am, expr_integer(&am, 4),
+	        expr_pair(&am, expr_integer(&am, 3), expr_empty_list(&am))));
+	am.val->atom.prim_proc(&am);
+
+	TEST_ASSERT_NOT_NULL(am.val);
+	TEST_ASSERT_TRUE(am.val->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, am.val->atom.type);
+	TEST_ASSERT_EQUAL(-2, am.val->atom.integer);
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_add_empty_list_is_0);
+	RUN_TEST(test_add_1_2_3_is_6);
+	RUN_TEST(test_mul_empty_list_is_1);
+	RUN_TEST(test_mul_2_3_4_is_24);
+	RUN_TEST(test_sub_1_is_minus_1);
+	RUN_TEST(test_sub_5_4_3_is_minus_2);
+	return UNITY_END();
+}

tests/print_tests.c

@@ -0,0 +1,61 @@
+#include "print.h"
+#include "unity.h"
+
+#include <string.h>
+
+#define BUFFER_SIZE 256U
+
+static am_t am;
+static char buffer[BUFFER_SIZE];
+
+void setUp(void)
+{
+	memset(buffer, 0, BUFFER_SIZE);
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_integer_5(void)
+{
+	am.val = expr_integer(&am, 5);
+	const size_t len = print(&am, buffer, BUFFER_SIZE);
+	TEST_ASSERT_EQUAL(1, len);
+	TEST_ASSERT_EQUAL_MEMORY("5", buffer, 1);
+}
+
+static void test_integer_1234(void)
+{
+	am.val = expr_integer(&am, 1234);
+	const size_t len = print(&am, buffer, BUFFER_SIZE);
+	TEST_ASSERT_EQUAL(4, len);
+	TEST_ASSERT_EQUAL_MEMORY("1234", buffer, 4);
+}
+
+static void test_integer_0(void)
+{
+	am.val = expr_integer(&am, 0);
+	const size_t len = print(&am, buffer, BUFFER_SIZE);
+	TEST_ASSERT_EQUAL(1, len);
+	TEST_ASSERT_EQUAL_MEMORY("0", buffer, 1);
+}
+
+static void test_integer_10(void)
+{
+	am.val = expr_integer(&am, 10);
+	const size_t len = print(&am, buffer, BUFFER_SIZE);
+	TEST_ASSERT_EQUAL(2, len);
+	TEST_ASSERT_EQUAL_MEMORY("10", buffer, 2);
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_integer_5);
+	RUN_TEST(test_integer_1234);
+	RUN_TEST(test_integer_0);
+	RUN_TEST(test_integer_10);
+	return UNITY_END();
+}

tests/read_tests.c

@@ -0,0 +1,98 @@
+#include "memory_stream.h"
+#include "read.h"
+#include "unity.h"
+
+#include <string.h>
+
+#define CAR(expr) (expr->pair.car)
+#define CDR(expr) (expr->pair.cdr)
+#define CADR(expr) CAR(CDR(expr))
+#define CDDR(expr) CDR(CDR(expr))
+#define CADDR(expr) CAR(CDDR(expr))
+#define CDDDR(expr) CDR(CDDR(expr))
+#define CAADDR(expr) CAR(CADDR(expr))
+#define CDADDR(expr) CDR(CADDR(expr))
+#define CADADDR(expr) CAR(CDADDR(expr))
+#define CDDADDR(expr) CDR(CDADDR(expr))
+#define CADDADDR(expr) CAR(CDDADDR(expr))
+#define CDDDADDR(expr) CDR(CDDADDR(expr))
+
+static am_t am;
+
+void setUp(void)
+{
+	am_init(&am);
+}
+
+void tearDown(void)
+{
+}
+
+static void test_nested_expression(void)
+{
+	const char *input = "(+ 1 (* 2 3))";
+	memory_stream_t stream;
+	memory_stream_init(&stream, (const uint8_t *)input, strlen(input));
+
+	read(&am, (stream_t *)&stream);
+
+	TEST_ASSERT_NOT_NULL(am.expr);
+	TEST_ASSERT_FALSE(am.expr->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CAR(am.expr));
+	TEST_ASSERT_TRUE(CAR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, CAR(am.expr)->atom.type);
+	TEST_ASSERT_EQUAL(1, CAR(am.expr)->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("+", CAR(am.expr)->atom.symbol.buf, 1);
+
+	TEST_ASSERT_NOT_NULL(CDR(am.expr));
+	TEST_ASSERT_FALSE(CDR(am.expr)->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CADR(am.expr));
+	TEST_ASSERT_TRUE(CADR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, CADR(am.expr)->atom.type);
+	TEST_ASSERT_EQUAL(1, CADR(am.expr)->atom.integer);
+
+	TEST_ASSERT_NOT_NULL(CDDR(am.expr));
+	TEST_ASSERT_FALSE(CDDR(am.expr)->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CADDR(am.expr));
+	TEST_ASSERT_FALSE(CADDR(am.expr)->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CAADDR(am.expr));
+	TEST_ASSERT_TRUE(CAADDR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_SYMBOL, CAADDR(am.expr)->atom.type);
+	TEST_ASSERT_EQUAL(1, CAADDR(am.expr)->atom.symbol.len);
+	TEST_ASSERT_EQUAL_MEMORY("*", CAADDR(am.expr)->atom.symbol.buf, 1);
+
+	TEST_ASSERT_NOT_NULL(CDADDR(am.expr));
+	TEST_ASSERT_FALSE(CDADDR(am.expr)->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CADADDR(am.expr));
+	TEST_ASSERT_TRUE(CADADDR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, CADADDR(am.expr)->atom.type);
+	TEST_ASSERT_EQUAL(2, CADADDR(am.expr)->atom.integer);
+
+	TEST_ASSERT_NOT_NULL(CDDADDR(am.expr));
+	TEST_ASSERT_FALSE(CDDADDR(am.expr)->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CADDADDR(am.expr));
+	TEST_ASSERT_TRUE(CADDADDR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, CADDADDR(am.expr)->atom.type);
+	TEST_ASSERT_EQUAL(3, CADDADDR(am.expr)->atom.integer);
+
+	TEST_ASSERT_NOT_NULL(CDDDADDR(am.expr));
+	TEST_ASSERT_TRUE(CDDDADDR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_EMPTY_LIST, CDDDADDR(am.expr)->atom.type);
+
+	TEST_ASSERT_NOT_NULL(CDDDR(am.expr));
+	TEST_ASSERT_TRUE(CDDDR(am.expr)->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_EMPTY_LIST, CDDDR(am.expr)->atom.type);
+}
+
+int main(void)
+{
+	UNITY_BEGIN();
+	RUN_TEST(test_nested_expression);
+	return UNITY_END();
+}

tests/store_tests.c

@@ -1,11 +1,11 @@
-#include "store.h"
+#include "am.h"
 #include "unity.h"
 
-static store_t store;
+static am_t am;
 
 void setUp(void)
 {
-	store_init(&store);
+	am_init(&am);
 }
 
 void tearDown(void)
@@ -14,14 +14,14 @@ void tearDown(void)
 
 static void test_alloc_returns_non_null_after_init(void)
 {
-	const expr_t *const expr = store_alloc(&store);
+	const expr_t *const expr = store_alloc(&am);
 	TEST_ASSERT_NOT_NULL(expr);
 }
 
 static void test_two_calls_to_alloc_return_distinct(void)
 {
-	const expr_t *const a = store_alloc(&store);
+	const expr_t *const a = store_alloc(&am);
-	const expr_t *const b = store_alloc(&store);
+	const expr_t *const b = store_alloc(&am);
 	TEST_ASSERT_NOT_EQUAL(a, b);
 }