to a B<BIGNUM> and stores it in **B<bn>. If *B<bn> is NULL, a new
B<BIGNUM> is created. If B<bn> is NULL, it only computes the number's
length in hexadecimal digits. If the string starts with '-', the
-number is negative. BN_dec2bn() is the same using the decimal system.
+number is negative.
+A "negative zero" is converted to zero.
+BN_dec2bn() is the same using the decimal system.
BN_print() and BN_print_fp() write the hexadecimal encoding of B<a>,
with a leading '-' for negative numbers, to the B<BIO> or B<FILE>
BN_bin2bn() returns the B<BIGNUM>, NULL on error.
BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL
-on error. BN_hex2bn() and BN_dec2bn() return the number's length in
-hexadecimal or decimal digits, and 0 on error.
+on error. BN_hex2bn() and BN_dec2bn() return the number of characters
+used in parsing, or 0 on error, in which
+case no new B<BIGNUM> will be created.
BN_print_fp() and BN_print() return 1 on success, 0 on write errors.