diff --git a/src/core/string.c b/src/core/string.c
index 063525c3..6c95390f 100644
--- a/src/core/string.c
+++ b/src/core/string.c
@@ -164,7 +164,7 @@ static void integer_to_string_b(JanetBuffer *buffer, int32_t x) {
 #define HEX(i) (((uint8_t *) janet_base64)[(i)])
 
 /* Returns a string description for a pointer. Truncates
- * title to 12 characters */
+ * title to 32 characters */
 static int32_t string_description_impl(uint8_t *buf, const char *title, void *pointer) {
     uint8_t *c = buf;
     int32_t i;
@@ -607,7 +607,7 @@ JanetBuffer *janet_pretty(JanetBuffer *buffer, int depth, Janet x) {
 }
 
 /* Helper function for formatting strings. Useful for generating error messages and the like.
- * Similiar to printf, but specialized for operating with janet. */
+ * Similar to printf, but specialized for operating with janet. */
 const uint8_t *janet_formatc(const char *format, ...) {
     va_list args;
     int32_t len = 0;
@@ -1246,7 +1246,7 @@ static const JanetReg cfuns[] = {
     },
     {"string/replace", cfun_replace,
         "(string/replace patt subst str)\n\n"
-        "Replace the first occurrence of patt with subst in the the string str. "
+        "Replace the first occurrence of patt with subst in the string str. "
         "Will return the new string if patt is found, otherwise returns str."
     },
     {"string/replace-all", cfun_replaceall,
@@ -1287,7 +1287,7 @@ static const JanetReg cfuns[] = {
     },
     {"string/pretty", cfun_pretty,
         "(string/pretty x [,depth=4 [,buffer=@\"\"]])\n\n"
-        "Pretty prints a value to a buffer. Optionally allwos setting max "
+        "Pretty prints a value to a buffer. Optionally allows setting max "
         "recursion depth, as well as writing to a buffer. Returns the buffer."
     },
     {NULL, NULL, NULL}
diff --git a/src/core/strtod.c b/src/core/strtod.c
index 2f2a4f83..f3aa13bc 100644
--- a/src/core/strtod.c
+++ b/src/core/strtod.c
@@ -104,7 +104,8 @@ static void bignat_append(struct BigNat *mant, uint32_t dig) {
 }
 
 /* Multiply the mantissa mant by a factor and the add a term
- * in one operation. Both factor and term will be between 2 and 36. */
+ * in one operation. factor will be between 2 and 36^4, 
+ * term will be between 0 and 36. */
 static void bignat_muladd(struct BigNat *mant, uint32_t factor, uint32_t term) {
     int32_t i;
     uint64_t carry = ((uint64_t) mant->first_digit) * factor + term;
@@ -215,10 +216,9 @@ static double convert(
      * Get exponent to zero while holding X constant. */
 
     /* Positive exponents are simple */
-    while (exponent > 0) {
-        bignat_muladd(mant, base, 0);
-        exponent--;
-    }
+    for (;exponent > 3; exponent -= 4) bignat_muladd(mant, base * base * base * base, 0);
+    for (;exponent > 1; exponent -= 2) bignat_muladd(mant, base * base, 0);
+    for (;exponent > 0; exponent -= 1) bignat_muladd(mant, base, 0);
 
     /* Negative exponents are tricky - we don't want to loose bits
      * from integer division, so we need to premultiply. */
@@ -226,10 +226,9 @@ static double convert(
         int32_t shamt = 5 - exponent / 4;
         bignat_lshift_n(mant, shamt);
         exponent2 -= shamt * BIGNAT_NBIT;
-        while (exponent < 0) {
-            bignat_div(mant, base);
-            exponent++;
-        }
+        for (;exponent < -3; exponent += 4) bignat_div(mant, base * base * base * base);
+        for (;exponent < -2; exponent += 2) bignat_div(mant, base * base);
+        for (;exponent <  0; exponent += 1) bignat_div(mant, base);
     }
 
     return negative