allocator: rework alloc_delete

Added a switch case at start of alloc_delete to only run it on
container (read: heap allocated) types.

If adding to free vector, iterate through free vector first to ensure
we've not added it already.  Reset the object before adding it, so
reuse is trivial.

Makefile

@@ -5,7 +5,7 @@ OUT=$(DIST)/alisp.out
 TEST=$(DIST)/test.out
 
 LDFLAGS=
-GFLAGS=-Wall -Wextra -Wpedantic -Werror -std=c23 -I./include/
+GFLAGS=-Wall -Wextra -Wswitch-enum -Wpedantic -Werror -std=c23 -I./include/
 DFLAGS=-ggdb -fsanitize=address -fsanitize=undefined
 RFLAGS=-O3
 
@@ -19,8 +19,8 @@ CFLAGS=$(GFLAGS) $(DFLAGS) -DVERBOSE_LOGS=2 -DTEST_VERBOSE=1
 endif
 
 # Units to compile
-UNITS=src/sv.c src/vec.c src/stream.c src/symtable.c src/lisp.c src/allocator.c \
-		src/sys.c src/reader.c
+UNITS=src/sv.c src/vec.c src/string.c src/stream.c src/symtable.c src/lisp.c \
+		src/allocator.c src/sys.c src/reader.c
 OBJECTS:=$(patsubst src/%.c, $(DIST)/%.o, $(UNITS))
 
 TEST_UNITS=test/main.c

include/alisp/allocator.h

@@ -15,10 +15,14 @@
 
 typedef struct
 {
+  u64 padding : 56;
+  tag_t tag   : 8;
   u64 references;
-  tag_t tag : 8;
 } alloc_metadata_t;
 
+static_assert(sizeof(alloc_metadata_t) == 16,
+              "16 byte metadata required for alignment purposes");
+
 typedef struct
 {
   alloc_metadata_t metadata;

include/alisp/lisp.h

@@ -10,7 +10,7 @@
 
 #include <stdio.h>
 
-#include <alisp/symtable.h>
+#include <alisp/string.h>
 #include <alisp/vec.h>
 
 #define NIL 0
@@ -26,59 +26,50 @@ typedef struct
 /// Tagging system
 typedef enum Tag
 {
-  TAG_NIL  = 0b00000000, // Start of atomic types
-  TAG_INT  = 0b00000001, // Special tag so we can encode 63 bit integers
-  TAG_SYM  = 0b00000100,
-  TAG_CONS = 0b00000010, // Start of container types
-  TAG_VEC  = 0b00000110,
-  NUM_TAGS = 5,
+  TAG_SMI  = 0b00000001, // Atomic types
+  TAG_SYM  = 0b00000011,
+  TAG_NIL  = 0b00000000, // Container types (0 LSB)
+  TAG_CONS = 0b00000010,
+  TAG_VEC  = 0b00000100,
+  TAG_STR  = 0b00000110,
+  NUM_TAGS = 6,
 } tag_t;
 
-static_assert(NUM_TAGS == 5, "Expected NUM_TAGS == 5 for enum SHIFT");
-enum Shift
-{
-  SHIFT_INT  = 1,
-  SHIFT_SYM  = 8,
-  SHIFT_CONS = 8,
-  SHIFT_VEC  = 8,
-};
-
-static_assert(NUM_TAGS == 5, "Expected NUM_TAGS == 5 for enum MASK");
-enum Mask
-{
-  MASK_INT  = 0b00000001,
-  MASK_SYM  = 0b11111111,
-  MASK_CONS = 0b11111111,
-  MASK_VEC  = 0b11111111,
-};
-
 // Some helper macros for tagging
-#define TAG(PTR, TYPE)    ((lisp_t *)(((PTR) << SHIFT_##TYPE) | TAG_##TYPE))
-#define IS_TAG(PTR, TYPE) (((u64)(PTR) & MASK_##TYPE) == TAG_##TYPE)
-#define UNTAG(PTR, TYPE)  (((u64)PTR) >> SHIFT_##TYPE)
+#define SHIFT_TAG (8)
+#define MASK_TAG  ((1 << SHIFT_TAG) - 1)
 
-#define INT_MAX ((((i64)1) << 62) - 1)
-#define INT_MIN (-(((i64)1) << 62))
+#define TAG(PTR, TYPE)    ((lisp_t *)((((u64)(PTR)) << SHIFT_TAG) | TAG_##TYPE))
+#define UNTAG(PTR)        (((u64)PTR) >> SHIFT_TAG)
+#define GET_TAG(PTR)      ((tag_t)(((u64)(PTR)) & MASK_TAG))
+#define IS_TAG(PTR, TYPE) (GET_TAG(PTR) == TAG_##TYPE)
 
-tag_t get_tag(const lisp_t *);
-lisp_t *tag_int(const i64);
+#define INT_BITS ((sizeof(i64) * 8) - SHIFT_TAG)
+#define INT_MAX  ((((i64)1) << (INT_BITS - 1)) - 1)
+#define INT_MIN  (-(INT_MAX + 1))
+
+tag_t tag_get(const lisp_t *);
+u64 tag_sizeof(tag_t);
+u64 lisp_sizeof(lisp_t *);
+lisp_t *lisp_reset(lisp_t *);
+void lisp_print(FILE *, lisp_t *);
+
+lisp_t *tag_smi(const i64);
 lisp_t *tag_sym(const char *);
 lisp_t *tag_cons(const cons_t *);
 lisp_t *tag_vec(const vec_t *);
+lisp_t *tag_str(const str_t *);
 lisp_t *tag_generic(void *, tag_t);
 
-i64 as_int(lisp_t *);
+i64 as_smi(lisp_t *);
 char *as_sym(lisp_t *);
 cons_t *as_cons(lisp_t *);
 vec_t *as_vec(lisp_t *);
+str_t *as_str(lisp_t *);
 
 #define CAR(L) (as_cons(L)->car)
 #define CDR(L) (as_cons(L)->cdr)
 
-void lisp_print(FILE *, lisp_t *);
-u64 tag_sizeof(tag_t);
-u64 lisp_sizeof(lisp_t *);
-
 #endif
 
 /* Copyright (C) 2026 Aryadev Chavali

include/alisp/reader.h

@@ -17,6 +17,7 @@ typedef enum
   READ_ERR_EOF,
   READ_ERR_EXPECTED_CLOSED_BRACE,
   READ_ERR_EXPECTED_CLOSED_SQUARE_BRACKET,
+  READ_ERR_EXPECTED_CLOSING_SPEECHMARKS,
   READ_ERR_UNEXPECTED_CLOSED_BRACE,
   READ_ERR_UNEXPECTED_CLOSED_SQUARE_BRACKET,
   READ_ERR_UNKNOWN_CHAR,

include/alisp/string.h

@@ -0,0 +1,35 @@
+/* string.h: String library
+ * Created: 2026-03-05
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef STRING_H
+#define STRING_H
+
+#include <alisp/sv.h>
+#include <alisp/vec.h>
+
+typedef struct
+{
+  vec_t data;
+} str_t;
+
+str_t string_make(sv_t sv);
+sv_t string_sv(str_t *);
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

include/alisp/sys.h

@@ -10,6 +10,7 @@
 
 #include <alisp/allocator.h>
 #include <alisp/lisp.h>
+#include <alisp/symtable.h>
 
 /// System context
 typedef struct
@@ -20,6 +21,7 @@ typedef struct
 
 void sys_init(sys_t *);
 lisp_t *sys_alloc(sys_t *, tag_t type);
+void sys_delete(sys_t *, lisp_t *);
 void sys_free(sys_t *);
 
 // Debugging function: provides total memory usage from system.
@@ -27,15 +29,17 @@ u64 sys_cost(sys_t *);
 
 /// Constructors and general Lisp API
 lisp_t *make_int(i64);
-lisp_t *make_vec(sys_t *, u64);
 lisp_t *intern(sys_t *, sv_t);
 lisp_t *cons(sys_t *, lisp_t *, lisp_t *);
+lisp_t *make_list(sys_t *, lisp_t **, u64);
+lisp_t *make_vec(sys_t *, u64);
+lisp_t *make_str(sys_t *, u64);
 
 lisp_t *car(lisp_t *);
 lisp_t *cdr(lisp_t *);
 
-void lisp_free(lisp_t *);
-void lisp_free_rec(lisp_t *);
+void lisp_free(sys_t *, lisp_t *);
+void lisp_free_rec(sys_t *, lisp_t *);
 
 #endif
 

include/alisp/vec.h

@@ -31,9 +31,12 @@ static_assert(sizeof(vec_t) == 64, "vec_t has to be 64 bytes as part of SBO");
 
 #define VEC_GET(V, I, T) (((T *)vec_data(V))[I])
 #define VEC_SIZE(V, T)   ((V)->size / (sizeof(T)))
+#define FOR_VEC(INDEX, V, T) \
+  for (size_t INDEX = 0; INDEX < VEC_SIZE(V, T); ++INDEX)
 
 void vec_init(vec_t *, u64);
 void vec_free(vec_t *);
+void vec_reset(vec_t *);
 u8 *vec_data(vec_t *);
 
 // Append, possibly reallocating memory

src/allocator.c

@@ -23,6 +23,8 @@ alloc_node_t *make_node(page_t *page, tag_t type)
 {
   alloc_node_t *node = NULL;
   u64 size           = sizeof(*node);
+
+  static_assert(NUM_TAGS == 6);
   switch (type)
   {
   case TAG_CONS:
@@ -31,8 +33,11 @@ alloc_node_t *make_node(page_t *page, tag_t type)
   case TAG_VEC:
     size += sizeof(vec_t);
     break;
+  case TAG_STR:
+    size += sizeof(str_t);
+    break;
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -52,7 +57,9 @@ alloc_node_t *make_node(page_t *page, tag_t type)
 alloc_node_t *lisp_to_node(lisp_t *lisp)
 {
   void *raw_ptr = NULL;
-  switch (get_tag(lisp))
+
+  static_assert(NUM_TAGS == 6);
+  switch (tag_get(lisp))
   {
   case TAG_CONS:
     raw_ptr = as_cons(lisp);
@@ -60,8 +67,11 @@ alloc_node_t *lisp_to_node(lisp_t *lisp)
   case TAG_VEC:
     raw_ptr = as_vec(lisp);
     break;
+  case TAG_STR:
+    raw_ptr = as_str(lisp);
+    break;
   case TAG_NIL: // These shouldn't be allocated
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -74,13 +84,15 @@ alloc_node_t *lisp_to_node(lisp_t *lisp)
 
 lisp_t *alloc_make(alloc_t *alloc, tag_t type)
 {
+  static_assert(NUM_TAGS == 6);
   switch (type)
   {
   case TAG_CONS:
   case TAG_VEC:
+  case TAG_STR:
     break;
   case TAG_NIL: // These shouldn't be allocated
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -123,7 +135,7 @@ lisp_t *alloc_make(alloc_t *alloc, tag_t type)
 
   // We couldn't get anything from the free vector, so try to allocate a fresh
   // one against one of the pages.
-  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  FOR_VEC(i, &alloc->pages, page_t *)
   {
     page_t *page = VEC_GET(&alloc->pages, i, page_t *);
     node         = make_node(page, type);
@@ -146,15 +158,42 @@ end:
 
 void alloc_delete(alloc_t *alloc, lisp_t *lisp)
 {
+  switch (tag_get(lisp))
+  {
+  case TAG_CONS:
+  case TAG_VEC:
+  case TAG_STR:
+    break;
+  case TAG_NIL: // These can't be deleted (not allocated)
+  case TAG_SMI:
+  case TAG_SYM:
+  default:
+    FAIL("Unreachable");
+    return;
+  }
+
   alloc_node_t *node = lisp_to_node(lisp);
   assert(node && node->metadata.references == 0);
+
+  // If already present in the free vector, stop.
+  FOR_VEC(i, &alloc->free_vec, alloc_node_t *)
+  {
+    alloc_node_t *other = VEC_GET(&alloc->pages, i, alloc_node_t *);
+    if (other == node)
+    {
+      return;
+    }
+  }
+
+  // Otherwise, add to the free vector.
+  lisp_reset(lisp);
   vec_append(&alloc->free_vec, &node, sizeof(node));
 }
 
 u64 alloc_cost(alloc_t *alloc)
 {
   u64 total_size = alloc->pages.size;
-  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  FOR_VEC(i, &alloc->pages, page_t *)
   {
     page_t *page = VEC_GET(&alloc->pages, i, page_t *);
     total_size += page->data.size;
@@ -164,14 +203,16 @@ u64 alloc_cost(alloc_t *alloc)
 
 void alloc_free(alloc_t *alloc)
 {
-  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  FOR_VEC(i, &alloc->pages, page_t *)
   {
     page_t *page = VEC_GET(&alloc->pages, i, page_t *);
-    // Iterate through every alloc_node in this page
+    // Iterate through every alloc_node in this page (dynamic walk)
     for (u64 j = 0; j < VEC_SIZE(&page->data, u8);)
     {
       alloc_node_t *node = (alloc_node_t *)(vec_data(&page->data) + j);
       u64 next           = sizeof(*node) + tag_sizeof(node->metadata.tag);
+
+      static_assert(NUM_TAGS == 6);
       switch (node->metadata.tag)
       {
       case TAG_CONS:
@@ -180,8 +221,11 @@ void alloc_free(alloc_t *alloc)
       case TAG_VEC:
         vec_free((vec_t *)node->data);
         break;
+      case TAG_STR:
+        vec_free(&((str_t *)node->data)->data);
+        break;
       case TAG_NIL:
-      case TAG_INT:
+      case TAG_SMI:
       case TAG_SYM:
       default:
         FAIL("Unreachable");

src/lisp.c

@@ -10,98 +10,107 @@
 
 #include <alisp/lisp.h>
 
-lisp_t *tag_int(i64 i)
+lisp_t *tag_smi(i64 i)
 {
-  return TAG((u64)i, INT);
+  return TAG(i, SMI);
 }
 
 lisp_t *tag_sym(const char *str)
 {
-  return TAG((u64)str, SYM);
+  return TAG(str, SYM);
 }
 
 lisp_t *tag_vec(const vec_t *vec)
 {
-  return TAG((u64)vec, VEC);
+  return TAG(vec, VEC);
+}
+
+lisp_t *tag_str(const str_t *str)
+{
+  return TAG(str, STR);
 }
 
 lisp_t *tag_cons(const cons_t *cons)
 {
-  return TAG((u64)cons, CONS);
+  return TAG(cons, CONS);
 }
 
 lisp_t *tag_generic(void *ptr, tag_t type)
 {
+  static_assert(NUM_TAGS == 6);
   switch (type)
   {
   case TAG_NIL:
-    return NIL;
-  case TAG_INT:
-    return tag_int((i64)ptr);
+    return TAG(ptr, NIL);
+  case TAG_SMI:
+    return tag_smi((i64)ptr);
   case TAG_SYM:
     return tag_sym(ptr);
   case TAG_CONS:
     return tag_cons(ptr);
   case TAG_VEC:
     return tag_vec(ptr);
+  case TAG_STR:
+    return tag_str(ptr);
   default:
     FAIL("Unreachable");
     return NIL;
   }
 }
 
-tag_t get_tag(const lisp_t *lisp)
+tag_t tag_get(const lisp_t *lisp)
 {
-  static_assert(NUM_TAGS == 5);
-  if (!lisp)
-    return TAG_NIL;
-  else if (IS_TAG(lisp, INT))
-    return TAG_INT;
-
-  return (u64)lisp & 0xFF;
+  return GET_TAG(lisp);
 }
 
-i64 as_int(lisp_t *obj)
+i64 as_smi(lisp_t *obj)
 {
-  assert(IS_TAG(obj, INT));
-  u64 p_obj = (u64)obj;
-  return UNTAG(p_obj, INT) |               // Delete the tag
-         (NTH_BYTE(p_obj, 7) & 0x80) << 56 // duplicate the MSB (preserve sign)
-      ;
+  assert(IS_TAG(obj, SMI));
+  u64 raw_obj = UNTAG(obj);
+  u64 msb     = (NTH_BYTE(raw_obj, 6) & 0x80) >> 7;
+  msb         = ((1LU << 8) - msb) << 56;
+  return (i64)(raw_obj | msb);
 }
 
 char *as_sym(lisp_t *obj)
 {
   assert(IS_TAG(obj, SYM));
-  return (char *)UNTAG(obj, SYM);
+  return (char *)UNTAG(obj);
 }
 
 cons_t *as_cons(lisp_t *obj)
 {
   assert(IS_TAG(obj, CONS));
-  return (cons_t *)UNTAG(obj, CONS);
+  return (cons_t *)UNTAG(obj);
+}
+
+str_t *as_str(lisp_t *obj)
+{
+  assert(IS_TAG(obj, STR));
+  return (str_t *)UNTAG(obj);
 }
 
 vec_t *as_vec(lisp_t *obj)
 {
   assert(IS_TAG(obj, VEC));
-  return (vec_t *)UNTAG(obj, VEC);
+  return (vec_t *)UNTAG(obj);
 }
 
 void lisp_print(FILE *fp, lisp_t *lisp)
 {
   if (!fp)
     return;
-  switch (get_tag(lisp))
+  static_assert(NUM_TAGS == 6);
+  switch (tag_get(lisp))
   {
   case TAG_NIL:
     fprintf(fp, "NIL");
     break;
-  case TAG_INT:
+  case TAG_SMI:
 #if VERBOSE_LOGS == 2
     fprintf(fp, "INT[");
 #endif
-    fprintf(fp, "%ld", as_int(lisp));
+    fprintf(fp, "%ld", as_smi(lisp));
 #if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #endif
@@ -161,11 +170,11 @@ void lisp_print(FILE *fp, lisp_t *lisp)
 #endif
 
     vec_t *vec = as_vec(lisp);
-    for (u64 i = 1; i <= VEC_SIZE(vec, lisp_t *); ++i)
+    FOR_VEC(i, vec, lisp_t *)
     {
-      lisp_t *item = VEC_GET(vec, i - 1, lisp_t *);
+      lisp_t *item = VEC_GET(vec, i, lisp_t *);
       lisp_print(fp, item);
-      if (i != VEC_SIZE(vec, lisp_t *))
+      if (i < VEC_SIZE(vec, lisp_t *) - 1)
       {
         fprintf(fp, " ");
       }
@@ -178,7 +187,24 @@ void lisp_print(FILE *fp, lisp_t *lisp)
 #endif
     break;
   }
-  case NUM_TAGS:
+  case TAG_STR:
+  {
+#if VERBOSE_LOGS == 2
+    fprintf(fp, "STR[");
+#else
+    fprintf(fp, "\"");
+#endif
+
+    sv_t sv = string_sv(as_str(lisp));
+    fprintf(fp, PR_SV, SV_FMT(sv));
+
+#if VERBOSE_LOGS == 2
+    fprintf(fp, "]");
+#else
+    fprintf(fp, "\"");
+#endif
+    break;
+  }
   default:
     FAIL("Unreachable");
     break;
@@ -187,18 +213,20 @@ void lisp_print(FILE *fp, lisp_t *lisp)
 
 u64 tag_sizeof(tag_t tag)
 {
+  static_assert(NUM_TAGS == 6);
   switch (tag)
   {
   case TAG_NIL:
     return 0;
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
     return sizeof(lisp_t *);
   case TAG_CONS:
     return sizeof(cons_t);
   case TAG_VEC:
     return sizeof(vec_t);
-  case NUM_TAGS:
+  case TAG_STR:
+    return sizeof(str_t);
   default:
     FAIL("Unreachable");
     return 0;
@@ -207,7 +235,41 @@ u64 tag_sizeof(tag_t tag)
 
 u64 lisp_sizeof(lisp_t *lisp)
 {
-  return tag_sizeof(get_tag(lisp));
+  return tag_sizeof(tag_get(lisp));
+}
+
+lisp_t *lisp_reset(lisp_t *lisp)
+{
+  switch (tag_get(lisp))
+  {
+  case TAG_NIL:
+  case TAG_SMI:
+  case TAG_SYM:
+    // Nothing to "reset" here.
+    return lisp;
+  case TAG_CONS:
+  {
+    // Make `car` and `cons` NIL
+    CAR(lisp) = NIL;
+    CDR(lisp) = NIL;
+    return lisp;
+  }
+  case TAG_VEC:
+  {
+    vec_reset(as_vec(lisp));
+    return lisp;
+  }
+  case TAG_STR:
+  {
+    vec_reset(&as_str(lisp)->data);
+    return lisp;
+  }
+  default:
+  {
+    FAIL("Unreachable");
+    return lisp;
+  }
+  }
 }
 
 /* Copyright (C) 2025, 2026 Aryadev Chavali

src/main.c

@@ -45,10 +45,10 @@ int main(int argc, char *argv[])
       VEC_SIZE(&ast, lisp_t *) == 1 ? "expr" : "exprs");
 
   {
-    for (u64 i = 0; i < VEC_SIZE(&ast, lisp_t *); ++i)
+    FOR_VEC(i, &ast, lisp_t *)
     {
-      lisp_t *expr = VEC_GET(&ast, i, lisp_t *);
 #if VERBOSE_LOGS
+      lisp_t *expr = VEC_GET(&ast, i, lisp_t *);
       printf("\t[%lu]: ", i);
       lisp_print(stdout, expr);
       printf("\n");

src/reader.c

@@ -20,11 +20,12 @@ const char *read_err_to_cstr(read_err_t err)
     return "EOF";
   case READ_ERR_UNKNOWN_CHAR:
     return "UNKNOWN_CHAR";
-    break;
   case READ_ERR_EXPECTED_CLOSED_BRACE:
     return "EXPECTED_CLOSED_BRACE";
   case READ_ERR_EXPECTED_CLOSED_SQUARE_BRACKET:
     return "EXPECTED_CLOSED_SQUARE_BRACKET";
+  case READ_ERR_EXPECTED_CLOSING_SPEECHMARKS:
+    return "EXPECTED_CLOSING_SPEECHMARKS";
   case READ_ERR_UNEXPECTED_CLOSED_BRACE:
     return "UNEXPECTED_CLOSED_BRACE";
   case READ_ERR_UNEXPECTED_CLOSED_SQUARE_BRACKET:
@@ -37,7 +38,7 @@ const char *read_err_to_cstr(read_err_t err)
 // Accepted characters for symbols.
 static const char *SYMBOL_CHARS =
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!$%&*+,-./"
-    ":<=>?@\\^_`{|}~0123456789";
+    ":<=>?@\\^_{|}~0123456789";
 
 // Little predicate using SYMBOL_CHARS
 bool is_sym(char c)
@@ -76,9 +77,9 @@ read_err_t read_int(sys_t *sys, stream_t *stream, lisp_t **ret)
     return read_sym(sys, stream, ret);
   }
 
-  if (digits_sv.size > 19)
+  if (digits_sv.size >= 18)
   {
-    TODO("alisp doesn't support big integers (bigger than 63 bits) yet");
+    TODO("alisp doesn't support big integers (bigger than 56 bits) yet");
   }
 
   i64 n = 0;
@@ -92,7 +93,7 @@ read_err_t read_int(sys_t *sys, stream_t *stream, lisp_t **ret)
     // => i > (INT_MAX - digit) / 10
     if (n > (INT_MAX - digit) / 10)
     {
-      TODO("alisp doesn't support big integers (bigger than 63 bits) yet");
+      TODO("alisp doesn't support big integers (bigger than 56 bits) yet");
     }
 
     n *= 10;
@@ -111,9 +112,7 @@ read_err_t read_negative(sys_t *sys, stream_t *stream, lisp_t **ret)
     read_err_t err = read_int(sys, stream, ret);
     if (err)
       return err;
-    i64 n = as_int(*ret);
-    n *= -1;
-    *ret = make_int(n);
+    *ret = make_int(as_smi(*ret) * -1);
     return READ_ERR_OK;
   }
   else if (is_sym(c) || isspace(c))
@@ -122,11 +121,14 @@ read_err_t read_negative(sys_t *sys, stream_t *stream, lisp_t **ret)
     return read_sym(sys, stream, ret);
   }
   else
+  {
     return READ_ERR_UNKNOWN_CHAR;
+  }
 }
 
 read_err_t read_list(sys_t *sys, stream_t *stream, lisp_t **ret)
 {
+  u64 old_pos = stream->position;
   // skip past the open parentheses '('
   (void)stream_next(stream);
 
@@ -138,7 +140,7 @@ read_err_t read_list(sys_t *sys, stream_t *stream, lisp_t **ret)
     read_err_t err = read(sys, stream, &item);
     if (err == READ_ERR_EOF)
     {
-      return READ_ERR_EXPECTED_CLOSED_BRACE;
+      goto no_close_brace;
     }
     else if (err)
     {
@@ -157,16 +159,23 @@ read_err_t read_list(sys_t *sys, stream_t *stream, lisp_t **ret)
   }
 
   if (stream_peek(stream) != ')')
-    return READ_ERR_EXPECTED_CLOSED_BRACE;
+  {
+    goto no_close_brace;
+  }
 
   stream_next(stream);
   *ret = top;
   return READ_ERR_OK;
+no_close_brace:
+  stream->position = old_pos;
+  return READ_ERR_EXPECTED_CLOSED_BRACE;
 }
 
 read_err_t read_vec(sys_t *sys, stream_t *stream, lisp_t **ret)
 {
+  u64 old_pos = stream->position;
   (void)stream_next(stream);
+
   lisp_t *container = make_vec(sys, 0);
   while (!stream_eoc(stream) && stream_peek(stream) != ']')
   {
@@ -174,7 +183,7 @@ read_err_t read_vec(sys_t *sys, stream_t *stream, lisp_t **ret)
     read_err_t err = read(sys, stream, &item);
     if (err == READ_ERR_EOF)
     {
-      return READ_ERR_EXPECTED_CLOSED_BRACE;
+      goto no_close_square_bracket;
     }
     else if (err)
     {
@@ -187,10 +196,33 @@ read_err_t read_vec(sys_t *sys, stream_t *stream, lisp_t **ret)
   }
 
   if (stream_peek(stream) != ']')
-    return READ_ERR_EXPECTED_CLOSED_SQUARE_BRACKET;
+    goto no_close_square_bracket;
+
   stream_next(stream);
   *ret = container;
   return READ_ERR_OK;
+no_close_square_bracket:
+  stream->position = old_pos;
+  return READ_ERR_EXPECTED_CLOSED_SQUARE_BRACKET;
+}
+
+read_err_t read_str(sys_t *sys, stream_t *stream, lisp_t **ret)
+{
+  u64 old_pos = stream->position;
+
+  (void)stream_next(stream);
+  sv_t contents = stream_till(stream, "\"");
+  if (stream_eoc(stream) || stream_peek(stream) != '\"')
+  {
+    stream->position = old_pos;
+    return READ_ERR_EXPECTED_CLOSING_SPEECHMARKS;
+  }
+
+  stream_next(stream);
+  lisp_t *lisp = make_str(sys, contents.size);
+  vec_append(&as_str(lisp)->data, contents.data, contents.size);
+  *ret = lisp;
+  return READ_ERR_OK;
 }
 
 read_err_t read_quote(sys_t *sys, stream_t *stream, lisp_t **ret)
@@ -200,8 +232,8 @@ read_err_t read_quote(sys_t *sys, stream_t *stream, lisp_t **ret)
   read_err_t err = read(sys, stream, &to_quote);
   if (err)
     return err;
-  *ret = cons(sys, to_quote, NIL);
-  *ret = cons(sys, intern(sys, SV_AUTO("quote")), *ret);
+  lisp_t *items[] = {intern(sys, SV_AUTO("quote")), to_quote};
+  *ret            = make_list(sys, items, ARRSIZE(items));
   return READ_ERR_OK;
 }
 
@@ -243,6 +275,8 @@ read_err_t read(sys_t *sys, stream_t *stream, lisp_t **ret)
     return read_vec(sys, stream, ret);
   else if (c == ']')
     return READ_ERR_UNEXPECTED_CLOSED_SQUARE_BRACKET;
+  else if (c == '\"')
+    return read_str(sys, stream, ret);
 
   return READ_ERR_UNKNOWN_CHAR;
 }

src/string.c

@@ -0,0 +1,44 @@
+/* string.c: String library implementation
+ * Created: 2026-03-05
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <string.h>
+
+#include <alisp/string.h>
+
+str_t string_make(sv_t sv)
+{
+  str_t string = {0};
+  if (sv.size)
+  {
+    vec_init(&string.data, sv.size);
+    if (sv.data)
+    {
+      memcpy(vec_data(&string.data), sv.data, sv.size);
+    }
+  }
+  return string;
+}
+
+sv_t string_sv(str_t *str)
+{
+  if (!str)
+    return SV(NULL, 0);
+  return SV((char *)vec_data(&str->data), str->data.size);
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/sys.c

@@ -17,14 +17,16 @@ void sys_init(sys_t *sys)
 
 lisp_t *sys_alloc(sys_t *sys, tag_t type)
 {
+  static_assert(NUM_TAGS == 6);
   switch (type)
   {
   case TAG_CONS:
   case TAG_VEC:
+  case TAG_STR:
     return alloc_make(&sys->memory, type);
   // Shouldn't be allocated
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
   default:
     FAIL("Unreachable");
@@ -32,6 +34,11 @@ lisp_t *sys_alloc(sys_t *sys, tag_t type)
   return NIL;
 }
 
+void sys_delete(sys_t *sys, lisp_t *lisp)
+{
+  alloc_delete(&sys->memory, lisp);
+}
+
 u64 sys_cost(sys_t *sys)
 {
   return alloc_cost(&sys->memory) + sym_table_cost(&sys->symtable);
@@ -46,7 +53,7 @@ void sys_free(sys_t *sys)
 
 lisp_t *make_int(i64 i)
 {
-  return tag_int(i);
+  return tag_smi(i);
 }
 
 lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
@@ -57,6 +64,17 @@ lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
   return cons;
 }
 
+lisp_t *make_list(sys_t *sys, lisp_t **lisps, u64 size)
+{
+  lisp_t *root = NIL;
+  for (u64 i = size; i > 0; --i)
+  {
+    lisp_t *node = lisps[i - 1];
+    root         = cons(sys, node, root);
+  }
+  return root;
+}
+
 lisp_t *make_vec(sys_t *sys, u64 capacity)
 {
   lisp_t *vec = sys_alloc(sys, TAG_VEC);
@@ -64,6 +82,13 @@ lisp_t *make_vec(sys_t *sys, u64 capacity)
   return vec;
 }
 
+lisp_t *make_str(sys_t *sys, u64 capacity)
+{
+  lisp_t *str = sys_alloc(sys, TAG_STR);
+  vec_init(&as_str(str)->data, capacity);
+  return str;
+}
+
 lisp_t *intern(sys_t *sys, sv_t sv)
 {
   const char *str = sym_table_find(&sys->symtable, sv);
@@ -86,57 +111,56 @@ lisp_t *cdr(lisp_t *lsp)
     return CDR(lsp);
 }
 
-void lisp_free(lisp_t *item)
+void lisp_free(sys_t *sys, lisp_t *lisp)
 {
-  switch (get_tag(item))
+  static_assert(NUM_TAGS == 6);
+  switch (tag_get(lisp))
   {
-  case TAG_CONS:
-    // Delete the cons
-    free(as_cons(item));
-    break;
+  case TAG_STR:
   case TAG_VEC:
-  {
-    vec_t *vec = as_vec(item);
-    vec_free(vec);
-    free(vec);
+  case TAG_CONS:
+    // Delete the underlying data
+    alloc_delete(&sys->memory, lisp);
     break;
-  }
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
-  case NUM_TAGS:
     // shouldn't be dealt with (either constant or dealt with elsewhere)
     break;
   }
 }
 
-void lisp_free_rec(lisp_t *item)
+void lisp_free_rec(sys_t *sys, lisp_t *item)
 {
-  switch (get_tag(item))
+  static_assert(NUM_TAGS == 6);
+  switch (tag_get(item))
   {
   case TAG_CONS:
   {
-    lisp_free_rec(car(item));
-    lisp_free_rec(cdr(item));
-    free(as_cons(item));
+    lisp_free_rec(sys, car(item));
+    lisp_free_rec(sys, cdr(item));
+    lisp_free(sys, item);
     break;
   }
   case TAG_VEC:
   {
     vec_t *vec = as_vec(item);
-    for (size_t i = 0; i < VEC_SIZE(vec, lisp_t **); ++i)
+    FOR_VEC(i, vec, lisp_t *)
     {
       lisp_t *allocated = VEC_GET(vec, i, lisp_t *);
-      lisp_free_rec(allocated);
+      lisp_free_rec(sys, allocated);
     }
-    vec_free(vec);
-    free(vec);
+    lisp_free(sys, item);
+    break;
+  }
+  case TAG_STR:
+  {
+    lisp_free(sys, item);
     break;
   }
   case TAG_NIL:
-  case TAG_INT:
+  case TAG_SMI:
   case TAG_SYM:
-  case NUM_TAGS:
     // shouldn't be dealt with (either constant or dealt with elsewhere)
     break;
   }

src/vec.c

@@ -38,6 +38,14 @@ void vec_free(vec_t *vec)
   memset(vec, 0, sizeof(*vec));
 }
 
+void vec_reset(vec_t *vec)
+{
+  if (!vec)
+    return;
+  memset(vec_data(vec), 0, vec->capacity);
+  vec->size = 0;
+}
+
 u8 *vec_data(vec_t *vec)
 {
   return vec->not_inlined ? vec->ptr : vec->inlined;

test/test_lisp_api.c

@@ -23,7 +23,7 @@ void smi_test(void)
   {
     i64 in       = ints[i];
     lisp_t *lisp = make_int(in);
-    i64 out      = as_int(lisp);
+    i64 out      = as_smi(lisp);
 
     TEST(in == out, "%ld == %ld", in, out);
   }
@@ -47,7 +47,7 @@ void smi_oob_test(void)
   {
     i64 in       = ints[i];
     lisp_t *lisp = make_int(in);
-    i64 out      = as_int(lisp);
+    i64 out      = as_smi(lisp);
 
     TEST(in != out, "%ld != %ld", in, out);
   }