7.7 Returning multiple values

7.7 Returning multiple values

Subroutines and functions often need to return more than one value, even simple ones. For example, a return value and error conditions. "C" uses pass by value for its function calls. This means that to get more than one value returned you need to pass the address of where you want the return value if you have more then one.

In this lab I want you to go quite a bit further than you did in lab 7.4: Numbers/Character Processing. I want you to write a program that returns (as its return value) the next number received as characters into its standard input.

The signed numbers can be in several formats:

If there is a "-" directly prior to the number it is a negative number.

zero binary and zero hexadecimal number respectively.

Numbers are terminated by any character that is not part of their set of characters. For example, an octal number is terminated by a 8 or a 9 and a binary number would be terminated by a 2. This terminating character should be "put back" with a call to ungetchar() so it can be used in the next number. For example, 0123456789 will first return a octal number of 1234567₈ and then a decimal value of 89₁₀.

A hexadecimal number can be terminated by any lower case letter.

Spaces, new lines, tabs, G-Z, and a-z terminate all numbers. Any special character or non-printing character also terminate all numbers.

The function prototype should look something like this:

int getnumber(int *radix, int *characters_read);

read from the input minus any put back.

At the start of your program print out:

• Your name
• CIS265 Louis Taber
• Lab: 7.7: Multiple return values

Write a program that process an input data doing the following:

• Process the input, looking for numbers, until the end-of-file condition occurs.
• For each number it finds it need to print out the following:
  • The decimal value of the number.
  • The input radix of the number.
• At the end of the program print out the sum of:
  1. All numbers.
  2. All numbers of a given radix.
  3. The number of characters processed.

Given the following example input.

abcde 0b0101 -012 123 0x05A -123

This output should be in (about) the following format:

Your name
CIS265  Louis Taber
Lab: 7.7: Multiple return values

Binary                      5
Octal                     -10
Decimal                   123
Hexadecimal                90
Decimal                  -123

EOF reached  ****************
Binary total                5
Octal total               -10
Decimal total               0
Hexadecimal total          90
Grand total                85
Total characters read      35

Test your program with the following sample data set.

This is the test data for the multiple returns lab.
If you have sixteen bit integers, create your own file.

0b11111 037 31 0x1F  Four thirty ones
-0b11111 -037 -31 -0x1F  Four negative thirty ones
2147483647 Decimal max
-2147483647 Almost decimal min  (sum now zero)

Run together numbers.
0b12 (Binary one, decimal two)
078  (Octal seven, decimal eight)
0xA0b10 (Hexadecimal One Hundred sixty, decimal ten)
This is the last line, no numbers

It is available by anonymous FTP at
ftp://lt.tucson.az.us/pub/c/return.dat.

Extra credit: Handle INT_MIN (-2147483648) correctly.

Turn in a copy of your program and its output when used with the above test data marked with:

• Your name
• TABER CIS265
• Lab 7.7: Returning multiple values
• The compiler and OS that you used.

Please turn your lab in to me, Louis Taber, during class, or slide it under the door of Santa Rita Building room A-115 (my office).

7.7 Returning multiple values