Hi Hugo,

You're correct, and I've updated the header file.

Cheers

Arran

"Hugo Smith" [email protected] wrote:

Hi Arran,

I found this function declaration in crypto.h

void vigenere_decrypt(char range_low, char range_high, int key, const char * cipher_text, char * plain_text);

can I assume that the key is supposed to be passed as a string instead of an int?

void vigenere_decrypt(char range_low, char range_high, const char * key, const char * cipher_text, char * plain_text);

Hi Taylah,

No, that's not a typo. Typically in related functions, we put input and output parameters in a consistent order. In the encryption function, cipher_text is an output. But in the decryption function, plain_text is the input, and cipher_text is the output. You can tell, because an input parameter is normally marked const, to indicate that it shouldn't be changed, whereas the output parameter is not (it's just a plain char *).

In some of the C library function, output parameters come first – e.g. memcpy, which has the prototype void *memcpy(void *dest, const void *src, size_t n). I'm not sure what the reasoning is, but in my code (and a lot of other C code I've seen), the output parameters tend to go at the end.

I hope that clarifies things! Let me know if you have any other questions.

cheers,

Arran

"Taylah Karran" [email protected] wrote:

Hey I think I've found another typo. In the pdf the caesar decrypt declaration has plain_text before cipher_text: void caesar_encrypt(char range_low, char range_high, int key, const char * plain_text, char * cipher_text); But crypto.h has them the other way around: void caesar_decrypt(char range_low, char range_high, int key, const char * cipher_text, char * plain_text);

Hi Arran,

Apologies, I copied the wrong function in my initial question, In the pdf the caesar decrypt declaration has plain_text before cipher_text:

void caesar_decrypt(char range_low, char range_high, int key, const char * plain_text, char * cipher_text);

But crypto.h has them the other way around:

void caesar_decrypt(char range_low, char range_high, int key, const char * cipher_text, char * plain_text);

So it throws an error when I go to compile.

Gotcha - the crypto.h version is the correct one (for the reasons I gave - the output parameter comes last).

So that's how you need to code your implementation - does that help?

Cheers

Arran

"Taylah Karran" [email protected] wrote:

Hi Arran,

Apologies, I copied the wrong function in my initial question, In the pdf the caesar decrypt declaration has plain_text before cipher_text:

void caesar_decrypt(char range_low, char range_high, int key, const char * plain_text, char * cipher_text);

But crypto.h has them the other way around:

void caesar_decrypt(char range_low, char range_high, int key, const char * cipher_text, char * plain_text);

So it throws an error when I go to compile.