08-04-24.html

08-04-24.mw

> currentdir();

(1)

> currentdir("/tmp");

(2)

> currentdir();

(3)

> plainfile:="/home/scott/www/mat331.spr08/problems/424-plain.txt";

(4)

> myFile:=fopen(plainfile, READ);

(5)

> line:=readline(myFile);

(6)

> line:=readline(myFile);

(7)

> line:=readline(myFile);

(8)

> line:=readline(myFile);

(9)

> line:=readline(myFile);

(10)

> fclose(myFile);

> myFile2:=fopen("aux.txt",WRITE);

(11)

> writeline(myFile2,"here is some stuff to put in the file. it could be a variable if we want.");

(12)

> fclose(myFile2);

> writeFile:= proc(nameFile::string, outFile::string)
local myFile, myOutput,line;
myFile:=fopen(nameFile,READ,TEXT);
myOutput:=fopen(outFile, WRITE,TEXT);
line:= readline(myFile);
while(line<>0)do
writeline(myOutput, line);
line:=readline(myFile);
od;
fclose(myFile);
fclose(myOutput);
end:

> with(StringTools):

> Alphabet:=cat(op(select( IsPrintable, [seq( convert([i],bytes), i=1..255)])));

?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~" align="center" border="0">
?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~" align="center" border="0">
?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~" align="center" border="0"> (13)

> StringToList := proc(text::string)
global Alphabet;
return(
[seq( SearchText(text[i], Alphabet) ,i=1..length(text))] );
end:

> ListToString := proc( numlist :: list(posint))
global Alphabet;
seq( Alphabet[numlist[i]], i=1..nops(numlist) );
end:

> AffineEncode := proc( plain::string, shift::integer, a::integer)
local nums,crypt, i;
global Alphabet;
nums := StringToList(plain);
crypt := ListToString(   [ seq(
                              modp(a*nums[i] + shift -1, length(Alphabet)) +1,
                              i=1..nops(nums)) ] );
return(cat(crypt));
end:

> encodeFile:= proc(nameFile::string, outFile::string, shift::integer, a::integer)
local myFile, myOutput,line;
myFile:=fopen(nameFile,READ,TEXT);
myOutput:=fopen(outFile, WRITE,TEXT);
line:= readline(myFile);
while(line<>0)do
line:=AffineEncode(line,shift,a);
writeline(myOutput, line);
line:=readline(myFile);
od;
fclose(myFile);
fclose(myOutput);
end: