Question

Hello again, I hope you can help me with this. I don't quite understand the difference between the functions build_coder and build_encoder in ps4. Can someone explain it to me? Thanks.

Answer 1

Judging by the response, we're all too lazy to find the code so that we can help. Post the functions.

Answer 2

Sure, there's no code, but this are the guidelines provided in the PS. I don't quite understand the difference between both.

After reading the guidelines again, I'm thinking that I could just define build_encoder to be a call to build_coder and return the dictionary built by the coder function.

def build_coder(shift):
"""
Returns a dict that can apply a Caesar cipher to a letter.
The cipher is defined by the shift value. Ignores non-letter characters
like punctuation and numbers.

shift: -27 < int < 27
returns: dict

Example:
>>> build_coder(3)
{' ': 'c', 'A': 'D', 'C': 'F', 'B': 'E', 'E': 'H', 'D': 'G', 'G': 'J',
'F': 'I', 'I': 'L', 'H': 'K', 'K': 'N', 'J': 'M', 'M': 'P', 'L': 'O',
'O': 'R', 'N': 'Q', 'Q': 'T', 'P': 'S', 'S': 'V', 'R': 'U', 'U': 'X',
'T': 'W', 'W': 'Z', 'V': 'Y', 'Y': 'A', 'X': ' ', 'Z': 'B', 'a': 'd',
'c': 'f', 'b': 'e', 'e': 'h', 'd': 'g', 'g': 'j', 'f': 'i', 'i': 'l',
'h': 'k', 'k': 'n', 'j': 'm', 'm': 'p', 'l': 'o', 'o': 'r', 'n': 'q',
'q': 't', 'p': 's', 's': 'v', 'r': 'u', 'u': 'x', 't': 'w', 'w': 'z',
'v': 'y', 'y': 'a', 'x': ' ', 'z': 'b'}
(The order of the key-value pairs may be different.)
"""
### TODO.

def build_encoder(shift):
"""
Returns a dict that can be used to encode a plain text. For example, you
could encrypt the plain text by calling the following commands
>>>encoder = build_encoder(shift)
>>>encrypted_text = apply_coder(plain_text, encoder)

The cipher is defined by the shift value. Ignores non-letter characters
like punctuation and numbers.

shift: 0 <= int < 27
returns: dict

Example:
>>> build_encoder(3)
{' ': 'c', 'A': 'D', 'C': 'F', 'B': 'E', 'E': 'H', 'D': 'G', 'G': 'J',
'F': 'I', 'I': 'L', 'H': 'K', 'K': 'N', 'J': 'M', 'M': 'P', 'L': 'O',
'O': 'R', 'N': 'Q', 'Q': 'T', 'P': 'S', 'S': 'V', 'R': 'U', 'U': 'X',
'T': 'W', 'W': 'Z', 'V': 'Y', 'Y': 'A', 'X': ' ', 'Z': 'B', 'a': 'd',
'c': 'f', 'b': 'e', 'e': 'h', 'd': 'g', 'g': 'j', 'f': 'i', 'i': 'l',
'h': 'k', 'k': 'n', 'j': 'm', 'm': 'p', 'l': 'o', 'o': 'r', 'n': 'q',
'q': 't', 'p': 's', 's': 'v', 'r': 'u', 'u': 'x', 't': 'w', 'w': 'z',
'v': 'y', 'y': 'a', 'x': ' ', 'z': 'b'}
(The order of the key-value pairs may be different.)

HINT : Use build_coder.
"""
### TODO.

Answer 3

Those outputs do appear to be identical, but the real proof is the Python code for each of those functions.

Answer 4

I noticed another problem with this problem set..
The dictionary example given is not correct, from memory I think there's two issues:
1) the encoded letters has an extra ' ' and missing a 'c'.
2) if the plaintext letters are listed [" ", a-z, A-Z]. Then a shift of 3 will not result in the order given in the example.