diff --git a/CMakeLists.txt b/CMakeLists.txt
index d16080c4..7674ff90 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -57,6 +57,7 @@ src/core/math.c
 src/core/native.c
 src/core/os.c
 src/core/string.c
+src/core/strtod.c
 src/core/struct.c
 src/core/symcache.c
 src/core/table.c
@@ -83,7 +84,6 @@ src/mainclient/line.h
 set(PARSER_SOURCES
 src/parser/ast.c
 src/parser/parse.c
-src/parser/strtod.c
 )
 
 set(TESTLIB_SOURCES
diff --git a/src/compiler/stl.c b/src/compiler/stl.c
index b89ef8b8..abd06413 100644
--- a/src/compiler/stl.c
+++ b/src/compiler/stl.c
@@ -37,8 +37,12 @@ static const DstReg cfuns[] = {
     {"string", dst_core_string},
     {"symbol", dst_core_symbol},
     {"buffer", dst_core_buffer},
+    {"format", dst_core_format},
     {"table", dst_core_table},
     {"array", dst_core_array},
+    {"scan-number", dst_core_scannumber},
+    {"scan-integer", dst_core_scaninteger},
+    {"scan-real", dst_core_scanreal},
     {"tuple", dst_core_tuple},
     {"struct", dst_core_struct},
     {"buffer", dst_core_buffer},
diff --git a/src/core/array.c b/src/core/array.c
index f5afef6e..c54e6e70 100644
--- a/src/core/array.c
+++ b/src/core/array.c
@@ -218,15 +218,20 @@ static int cfun_concat(DstArgs args) {
     return dst_return(args, args.v[0]);
 }
 
+static const DstReg cfuns[] = {
+    {"array-pop", cfun_pop},
+    {"array-peek", cfun_peek},
+    {"array-push", cfun_push},
+    {"array-setcount", cfun_setcount},
+    {"array-ensure", cfun_ensure},
+    {"array-slice", cfun_slice},
+    {"array-concat", cfun_concat},
+    {NULL, NULL}
+};
+
 /* Load the array module */
 int dst_lib_array(DstArgs args) {
     DstTable *env = dst_env_arg(args);
-    dst_env_def(env, "array-pop", dst_wrap_cfunction(cfun_pop));
-    dst_env_def(env, "array-peek", dst_wrap_cfunction(cfun_peek));
-    dst_env_def(env, "array-push", dst_wrap_cfunction(cfun_push));
-    dst_env_def(env, "array-setcount", dst_wrap_cfunction(cfun_setcount));
-    dst_env_def(env, "array-ensure", dst_wrap_cfunction(cfun_ensure));
-    dst_env_def(env, "array-slice", dst_wrap_cfunction(cfun_slice));
-    dst_env_def(env, "array-concat", dst_wrap_cfunction(cfun_concat));
+    dst_env_cfuns(env, cfuns);
     return 0;
 }
diff --git a/src/core/corelib.c b/src/core/corelib.c
index df0e5b09..a059e054 100644
--- a/src/core/corelib.c
+++ b/src/core/corelib.c
@@ -95,6 +95,82 @@ int dst_core_buffer(DstArgs args) {
     return dst_return(args, dst_wrap_buffer(b));
 }
 
+int dst_core_format(DstArgs args) {
+    const uint8_t *format;
+    int32_t i, len, n;
+    DstBuffer buf;
+    dst_minarity(args, 1);
+    dst_arg_bytes(format, len, args, 0);
+    n = 1;
+    dst_buffer_init(&buf, len);
+    for (i = 0; i < len; i++) {
+        uint8_t c = format[i];
+        if (c != '%') {
+            dst_buffer_push_u8(&buf, c);
+        } else {
+            if (++i == len) break;
+            c = format[i];
+            switch (c) {
+                default:
+                    dst_buffer_push_u8(&buf, c);
+                    break;
+                case 's':
+                {
+                    if (n >= args.n) goto noarg;
+                    dst_buffer_push_string(&buf, dst_to_string(args.v[n++]));
+                    break;
+                }
+            }
+        }
+    }
+    *args.ret = dst_wrap_string(dst_string(buf.data, buf.count));
+    dst_buffer_deinit(&buf);
+    return 0;
+noarg:
+    dst_buffer_deinit(&buf);
+    return dst_throw(args, "not enough arguments to format");
+}
+
+int dst_core_scannumber(DstArgs args) {
+    const uint8_t *data;
+    Dst x;
+    int32_t len;
+    dst_fixarity(args, 1);
+    dst_arg_bytes(data, len, args, 0);
+    x = dst_scan_number(data, len);
+    if (!dst_checktype(x, DST_INTEGER) && !dst_checktype(x, DST_REAL)) {
+        return dst_throw(args, "error parsing number");
+    }
+    return dst_return(args, x);
+}
+
+int dst_core_scaninteger(DstArgs args) {
+    const uint8_t *data;
+    int32_t len, ret;
+    int err = 0;
+    dst_fixarity(args, 1);
+    dst_arg_bytes(data, len, args, 0);
+    ret = dst_scan_integer(data, len, &err);
+    if (err) {
+        return dst_throw(args, "error parsing integer");
+    }
+    return dst_return(args, dst_wrap_integer(ret));
+}
+
+int dst_core_scanreal(DstArgs args) {
+    const uint8_t *data;
+    int32_t len;
+    double ret;
+    int err = 0;
+    dst_fixarity(args, 1);
+    dst_arg_bytes(data, len, args, 0);
+    ret = dst_scan_real(data, len, &err);
+    if (err) {
+        return dst_throw(args, "error parsing real");
+    }
+    return dst_return(args, dst_wrap_real(ret));
+}
+
 int dst_core_tuple(DstArgs args) {
     return dst_return(args, dst_wrap_tuple(dst_tuple_n(args.v, args.n)));
 }
@@ -137,7 +213,7 @@ int dst_core_gensym(DstArgs args) {
 }
 
 int dst_core_length(DstArgs args) {
-    dst_checkmany(args, 0, DST_TFLAG_LENGTHABLE);
+    dst_fixarity(args, 1);
     return dst_return(args, dst_wrap_integer(dst_length(args.v[0])));
 }
 
diff --git a/src/parser/strtod.c b/src/core/strtod.c
similarity index 98%
rename from src/parser/strtod.c
rename to src/core/strtod.c
index bfb21f65..b94e64aa 100644
--- a/src/parser/strtod.c
+++ b/src/core/strtod.c
@@ -211,7 +211,7 @@ static struct DstScanRes dst_scan_impl(
             /* underscores are ignored - can be used for separator */
         } else {
             int digit = digit_lookup[*str & 0x7F];
-            if (digit >= res.base) goto error;
+            if (*str > 127 || digit >= res.base) goto error;
             if (res.seenpoint) res.ex--;
             if (res.mant > 0x00ffffffffffffff)
                 res.ex++;
@@ -242,7 +242,7 @@ static struct DstScanRes dst_scan_impl(
         while (str < end && *str == '0') str++;
         while (str < end && ee < (INT32_MAX / 40)) {
             int digit = digit_lookup[*str & 0x7F];
-            if (digit >= res.base) goto error;
+            if (*str > 127 || digit >= res.base) goto error;
             ee = res.base * ee + digit;
             str++;
             seenadigit = 1;
diff --git a/src/include/dst/dst.h b/src/include/dst/dst.h
index 60e64b6e..8bb29efa 100644
--- a/src/include/dst/dst.h
+++ b/src/include/dst/dst.h
@@ -36,6 +36,11 @@ extern "C" {
 
 #include "dsttypes.h"
 
+/* Number scanning */
+Dst dst_scan_number(const uint8_t *src, int32_t len);
+int32_t dst_scan_integer(const uint8_t *str, int32_t len, int *err);
+double dst_scan_real(const uint8_t *str, int32_t len, int *err);
+
 /* Array functions */
 DstArray *dst_array(int32_t capacity);
 DstArray *dst_array_init(DstArray *array, int32_t capacity);
@@ -250,6 +255,13 @@ int dst_typeabstract_err(DstArgs args, int32_t n, DstAbstractType *at);
     dst_check(A, N, TYPE);\
     DEST = dst_unwrap_##NAME((A).v[(N)]); } while (0)
 
+#define dst_arg_bytes(DESTBYTES, DESTLEN, A, N) do {\
+    if ((A).n <= (N)) return dst_typemany_err(A, N, DST_TFLAG_BYTES);\
+    if (dst_chararray_view((A).v[(N)], &(DESTBYTES), &(DESTLEN))) {\
+        dst_typemany_err(A, N, DST_TFLAG_BYTES);\
+    }\
+} while (0)
+
 #define dst_arg_fiber(DEST, A, N) _dst_arg(DST_FIBER, fiber, DEST, A, N)
 #define dst_arg_integer(DEST, A, N) _dst_arg(DST_INTEGER, integer, DEST, A, N)
 #define dst_arg_real(DEST, A, N) _dst_arg(DST_REAL, real, DEST, A, N)
diff --git a/src/include/dst/dstcorelib.h b/src/include/dst/dstcorelib.h
index 838d362a..9b9473a2 100644
--- a/src/include/dst/dstcorelib.h
+++ b/src/include/dst/dstcorelib.h
@@ -84,6 +84,10 @@ int dst_core_describe(DstArgs args);
 int dst_core_string(DstArgs args);
 int dst_core_symbol(DstArgs args);
 int dst_core_buffer(DstArgs args);
+int dst_core_format(DstArgs args);
+int dst_core_scannumber(DstArgs args);
+int dst_core_scaninteger(DstArgs args);
+int dst_core_scanreal(DstArgs args);
 int dst_core_tuple(DstArgs args);
 int dst_core_array(DstArgs args);
 int dst_core_table(DstArgs args);
diff --git a/src/include/dst/dstparse.h b/src/include/dst/dstparse.h
index 7d7ef0d9..c9e08d6a 100644
--- a/src/include/dst/dstparse.h
+++ b/src/include/dst/dstparse.h
@@ -38,11 +38,6 @@ Dst dst_ast_unwrap(Dst x);
 typedef struct DstParseState DstParseState;
 typedef struct DstParser DstParser;
 
-/* Number scanning */
-Dst dst_scan_number(const uint8_t *src, int32_t len);
-int32_t dst_scan_integer(const uint8_t *str, int32_t len, int *err);
-double dst_scan_real(const uint8_t *str, int32_t len, int *err);
-
 enum DstParserStatus {
     DST_PARSE_ROOT,
     DST_PARSE_ERROR,
diff --git a/src/include/dst/dsttypes.h b/src/include/dst/dsttypes.h
index 022120eb..fed092d9 100644
--- a/src/include/dst/dsttypes.h
+++ b/src/include/dst/dsttypes.h
@@ -102,7 +102,7 @@ typedef enum DstType {
 #define DST_TFLAG_BOOLEAN (DST_TFLAG_TRUE | DST_TFLAG_FALSE)
 #define DST_TFLAG_NUMBER (DST_TFLAG_REAL | DST_TFLAG_INTEGER)
 #define DST_TFLAG_CALLABLE (DST_TFLAG_FUNCTION | DST_TFLAG_CFUNCTION)
-#define DST_TFLAG_CHARS (DST_TFLAG_STRING | DST_TFLAG_SYMBOL | DST_TFLAG_BUFFER)
+#define DST_TFLAG_BYTES (DST_TFLAG_STRING | DST_TFLAG_SYMBOL | DST_TFLAG_BUFFER)
 #define DST_TFLAG_INDEXED (DST_TFLAG_ARRAY | DST_TFLAG_TUPLE)
 #define DST_TFLAG_DICTIONARY (DST_TFLAG_TABLE | DST_TFLAG_STRUCT)
 #define DST_TFLAG_LENGTHABLE (DST_TFLAG_CHARS | DST_TFLAG_INDEXED | DST_TFLAG_DICTIONARY)
diff --git a/src/parser/parse.c b/src/parser/parse.c
index 8956a8aa..244fc199 100644
--- a/src/parser/parse.c
+++ b/src/parser/parse.c
@@ -86,7 +86,7 @@ The table contains 256 bits, where each bit is 1
 if the corresponding ascci code is a symbol char, and 0
 if not. The upper characters are also considered symbol
 chars and are then checked for utf-8 compliance. */
-static uint32_t symchars[8] = {
+static const uint32_t symchars[8] = {
 	0x00000000, 0xF7ffec72, 0xd7ffffff, 0x57fffffe,
 	0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff
 };
@@ -703,49 +703,6 @@ static int cfun_node(DstArgs args) {
     return dst_return(args, dst_wrap_tuple(dst_tuple_end(tup)));
 }
 
-static int cfun_parsenumber(DstArgs args) {
-    const uint8_t *data;
-    Dst x;
-    int32_t len;
-    if (args.n != 1) return dst_throw(args, "expected string or buffer");
-    if (!dst_chararray_view(args.v[0], &data, &len))
-        return dst_throw(args, "expected string or buffer");
-    x = dst_scan_number(data, len);
-    if (!dst_checktype(x, DST_INTEGER) && !dst_checktype(x, DST_REAL)) {
-        return dst_throw(args, "error parsing number");
-    }
-    return dst_return(args, x);
-}
-
-static int cfun_parseint(DstArgs args) {
-    const uint8_t *data;
-    int32_t len, ret;
-    int err = 0;
-    if (args.n != 1) return dst_throw(args, "expected string or buffer");
-    if (!dst_chararray_view(args.v[0], &data, &len))
-        return dst_throw(args, "expected string or buffer");
-    ret = dst_scan_integer(data, len, &err);
-    if (err) {
-        return dst_throw(args, "error parsing integer");
-    }
-    return dst_return(args, dst_wrap_integer(ret));
-}
-
-static int cfun_parsereal(DstArgs args) {
-    const uint8_t *data;
-    int32_t len;
-    double ret;
-    int err = 0;
-    if (args.n != 1) return dst_throw(args, "expected string or buffer");
-    if (!dst_chararray_view(args.v[0], &data, &len))
-        return dst_throw(args, "expected string or buffer");
-    ret = dst_scan_real(data, len, &err);
-    if (err) {
-        return dst_throw(args, "error parsing real");
-    }
-    return dst_return(args, dst_wrap_real(ret));
-}
-
 static const DstReg cfuns[] = {
     {"parser", cfun_parser},
     {"parser-produce", cfun_produce},
@@ -757,9 +714,6 @@ static const DstReg cfuns[] = {
     {"ast-unwrap1", cfun_unwrap1},
     {"ast-wrap", cfun_wrap},
     {"ast-node", cfun_node},
-    {"parse-number", cfun_parsenumber},
-    {"parse-int", cfun_parseint},
-    {"parse-real", cfun_parsereal},
     {NULL, NULL}
 };