WebliminalBlog

These topics came up in my CPSC 220 class today.
The course deals with C++ and we’ve worked with the string class.

Converting from ASCII to integer and from integer to ASCII
need to work with C strings rather than C++ strings.
The conversion is easy, though.
For this discussion suppose we have the declarations
#include
string si, sj;
int i, j;
si = “1234”; sj = “-3458”;

We can convert these strings to integers by using the function atoi as follows.

i = atoi(si.c_str()); j = atoi(sj.c_str());

We need to use the method c_str() of the string class, because atoi expects an argument of type char *.

To convert a decimal integer to a string, it’s easy if you
use sprintf as follows
i = 123;
sprintf(si.c_str(),”%d”,i);

The integer i is stored as a decimal (%d) integer and stored
in the string si.

For more info on these take a look at
http://www.iota-six.co.uk/c/g3_atoi_itoa_sprintf_sscanf.asp

Converting characters to their ASCII equivalent can be done
with an explicit cast as in
int i;
string si = “1234”;
i = int(si[3]);

In the case above i gets the value 52 which is the ASCII value
for ‘4’.

Converting the other way is quite natural as in
si[3] = char (i);

In this case s[3] has the same value as it started with.
That is,

si[3] = char ( int (si[3]) );