MaplePrimes - answers and comments on Question, Ascii converting help please

readbytes

alec — Sun, 05 Apr 2009 05:56:40 Z

writebytes("testing.txt","testing");

                                  7

close("testing.txt");
readbytes("testing.txt",infinity);

                 [116, 101, 115, 116, 105, 110, 103]

convert(%,bytes);

                              "testing"

Alec

question( In need of help badly)

Jabz — Sun, 05 Apr 2009 20:09:48 Z

These are the question i was asked

Q.1. Write a procedalure that takes a list of characters as input and returns a corresponding list of ASCII values as output

Q.2.i)Write a prcedure that takes as its 3 inputs 2 positive integers a and b and a list of numbers. Each element of the returned list should consist of the corresponding element of the input list, raised to the power of b and taken modulo a.

Q2. ii) Check that if your procedure is used to encrypt a list of numbers with parameters a=33 and b= 3 and then encrypt the result with parameters a=33 and b=3, the final list matches the original list.

Thank you

re

Jabz — Sun, 05 Apr 2009 18:57:13 Z

thank u for the post. I was really wondering how to convert the contents of a txt file without entering the content again.

For example

if i open a a file

filename := "C:\\Users\\x\\Desktop\\testing.txt":

Text[WriteLine]( filename, "FileTools example" );

what is the code that i have to type for maple to open the file read the data and convert into ascii and display it?

thank u

readbytes

alec — Mon, 06 Apr 2009 01:42:46 Z

close(filename);
readbytes(filename,18);

  [70, 105, 108, 101, 84, 111, 111, 108, 115, 32, 101, 120, 97, 109,

        112, 108, 101, 13]

Alec

Answers

alec — Mon, 06 Apr 2009 04:29:38 Z

Q.1. It is easier to convert a string,

convert("abc",bytes);

                             [97, 98, 99]

A list of characters can be converted using the following procedure,

f:=L->map(op@convert,L,bytes):

Another solution:

f:=curry(map,StringTools:-Ord);

For example,

L:=["a","b","c"]:
f(L);

                             [97, 98, 99]

Q.2.i)

F:=(a,b,L)->map(x->x&^b mod a,L):

Q2. ii)

L:=[$0..32];

  L := [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,

        18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]

L1:=F(33,3,L);

  L1 := [0, 1, 8, 27, 31, 26, 18, 13, 17, 3, 10, 11, 12, 19, 5, 9, 4,

        29, 24, 28, 14, 21, 22, 23, 30, 16, 20, 15, 7, 2, 6, 25, 32]

F(33,3,L1);

  [0, 1, 17, 15, 25, 20, 24, 19, 29, 27, 10, 11, 12, 28, 26, 3, 31, 2,

        30, 7, 5, 21, 22, 23, 6, 4, 14, 9, 13, 8, 18, 16, 32]

Nope. On the other hand,

F(33,7,L1);

  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,

        19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]

That matches the original list.

Alec

Yes it Works

Jabz — Mon, 06 Apr 2009 08:10:13 Z

Thank you so much now i can see clearly what's happenning.

much much appriciated