Function Calls
So, I'm working on functions and I'm trying to get everything together but when I try to build the program I receive an error stating:
"error c3861: 'toDigits': identifier not found"
The line it mentions has the error is 60
Any insight or suggestions would be amazing!
"error c3861: 'toDigits': identifier not found"
The line it mentions has the error is 60
Any insight or suggestions would be amazing!
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The function readDials doesn't know what the toDigit function is. The function prototypes can be moved out of and before the main function.
But then - the function prototype for toDigits doesn't match up with the function definition in terms of the parameters sent. And you have it set to return a char, but it only returns -1 in its default case.
function prototype
function definition
And I'm not sure what's supposed to happen with d in the toDigit function. A local variable is declared but not initialized, then used to determine the switch case. Did you mean to use the parameters that were sent in by reference?
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But then - the function prototype for toDigits doesn't match up with the function definition in terms of the parameters sent. And you have it set to return a char, but it only returns -1 in its default case.
function prototype
char toDigits(char &d); function definition
char toDigits(char &d2, char &d3, char &d4, char &d5, char &d6, char &d7, char &d8)default: return -1;And I'm not sure what's supposed to happen with d in the toDigit function. A local variable is declared but not initialized, then used to determine the switch case. Did you mean to use the parameters that were sent in by reference?
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Errors are gone, but the program does not run as intended.
The desired result should be as explained below:
The desired result should be as explained below:
Pseudocode
Main Function
Declare the char variables for the 8 digits of the phone number
while true
Call the ReadDials function passing the 8 digits
by reference. ReadDials returns an error code by
value.
If the return value is -5, exit the do while loop
If the error code is -1, display the
error message "ERROR - An invalid character was entered".
If the error code is -2, display the
error message "ERROR - Phone number cannot begin with 0".
If the error code is -3, display the
error message "ERROR - Phone number cannot begin with 555".
If the error code is -4, display the
error message "ERROR - Hyphen is not in the correct position".
Otherwise, call the AcknowledgeCall function
End-While
ReadDials function
Input the first digit
If a Q was entered, return -5.
Input the rest of the phone number
Call the ToDigit function for each of the 7 digits
not for digit 4
If ToDigit returns -1, return -1
If digit 4 is not a hyphen, return -4.
If digit 1 is 0, return -2.
If digits 1 - 3 are 5, return -3
Otherwise, return 0
ToDigit function
Convert the digit to upper case
Use a switch statement to determine if the digit is valid
and convert the letters to digits
If the digit is invalid, return -1.
If the digit is valid, return 0.
AcknowledgeCall function
Display the Phone Number.
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Enter a phone number (Q to quit): 213-2121 Phone Number Dialed: 213-2121 Enter a phone number (Q to quit): asc-dfer Phone Number Dialed: 272-3337 Enter a phone number (Q to quit): 555-resw ERROR - Phone number cannot begin with 555 Enter a phone number (Q to quit): 098-8765 ERROR - Phone number cannot begin with 0 Enter a phone number (Q to quit): 12345678 ERROR - Hyphen is not in the correct position Enter a phone number (Q to quit): @34-*uyt ERROR - An invalid character was entered Enter a phone number (Q to quit): Q Press any key to continue . . . |
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Generally it's not a good idea to global variables - it's OK to pull the function prototypes out of main, but not variable declarations.
What are the program and individual functions supposed to be doing? Is there a description of the problem that you can copy here?
What are the program and individual functions supposed to be doing? Is there a description of the problem that you can copy here?
Write a program that simulates the dialing of a phone number.
A user will input an 8-place number, for example: 359-3177 (note that the hyphen is considered a digit).
The rules for entering phone numbers follow.
• 8 places
• It may have numbers, letters, or both.
• The phone number cannot begin with 555.
• The phone number cannot begin with 0 or 1.
• The hyphen must be in the 4th position.
• No other characters (@#$%^&*()_+=\|/><etc.) are allowed.
• If a letter is entered, its output will be a number (check your phone pad).
• Enter Q to Quit.
If all of the rules are met, you will output a message to the console that reads like the following.
Phone Number Dialed: UN9-3177 *the number entered
If all of the rules are not met, then you output one of the following error messages to the console.
• ERROR - Phone number cannot begin with 555
• ERROR - Phone number cannot begin with 0
• ERROR - Hyphen is not in the correct position
• ERROR - An invalid character was entered
It will then prompt the user to try again.
---More---
Step 1: Requirements: Phone-Dialing Program
Write a program that simulates the dialing of a phone number.
A user will input an 8-place number, for example: 359-3177 (note that the hyphen is considered a digit).
The rules for entering phone numbers follow.
• 8 places
• It may have numbers, letters, or both.
• The phone number cannot begin with 555.
• The phone number cannot begin with 0 or 1.
• The hyphen must be in the 4th position.
• No other characters (@#$%^&*()_+=\|/><etc.) are allowed.
• If a letter is entered, its output will be a number (check your phone pad).
• Enter Q to Quit.
If all of the rules are met, you will output a message to the console that reads like the following.
Phone Number Dialed: UN9-3177 *the number entered
If all of the rules are not met, then you output one of the following error messages to the console.
• ERROR - Phone number cannot begin with 555
• ERROR - Phone number cannot begin with 0
• ERROR - Hyphen is not in the correct position
• ERROR - An invalid character was entered
It will then prompt the user to try again.
This should be a lot of fun!
Here are some great things to think about as you begin your program!
Define a function named ReadDials() that reads each digit and letter dialed into 8 separate char variables (DO NOT USE ARRAYS). All the digits are sent back through parameters by reference.
Then, for each digit, the program will use a function named ToDigit(), which receives a single char argument (pass by reference) that may be a number or a letter of one of the digits dialed.
If it is a number, then return 0 by value indicating that it is a valid digit. If the digit is a letter, then the number corresponding to the letter is returned by reference, and return 0 by value indicating that it is a valid digit. Here are the letters associated with each digit.
2;A B C
3;D E F
4;G H I
5 ;J K L
6 ;M N O
7; P Q R S
8; T U V
9; W X Y Z
If the digit entered is not one of the valid digits or one of the valid letters, return –1 by value indicating that you have an invalid digit.
A phone number never begins with a 0, so the program should flag an error if such a number is entered. Make ReadDials() return –2 in this case.
A phone number never begins with 555, so the program should flag an error if such a number is entered. Make ReadDials() return –3 in this case.
A phone number always has a hyphen (-) in the 4th position. Make ReadDials() return –4 in this case (if it doesn't have a hyphen in the 4th position). If a hyphen is in any other position, it is considered an invalid digit.
If the phone number is valid, the main calls the AcknowledgeCall function to write the converted number to the output file.
All the logic of the program should be put in functions that are called from Main(): ReadDials() and AcknowledgeCall().
The ToDigits() function is called from the ReadDials() function and is used to convert each letter entered individually into a digit and to verify that the user has entered a valid phone number. Have the program work for any number of phone numbers.
In the ToDigits() function uses the toupper function to convert any letters entered to uppercase. All the error messages are to be written to the output file from main() based on the return value from the functions.
Continue processing until the user enters a Q.
You will set up the 8 char variables to hold the digits of the phone number in main() and pass the variables to the functions by reference.
Sample Output from the Program
Enter a phone number (Q to quit): 213-2121
Phone Number Dialed: 213-2121
Enter a phone number (Q to quit): asc-dfer
Phone Number Dialed: 272-3337
Enter a phone number (Q to quit): 555-resw
ERROR - Phone number cannot begin with 555
Enter a phone number (Q to quit): 098-8765
ERROR - Phone number cannot begin with 0
Enter a phone number (Q to quit): 12345678
ERROR - Hyphen is not in the correct position
Enter a phone number (Q to quit): @34-*uyt
ERROR - An invalid character was entered
Enter a phone number (Q to quit): Q
Press any key to continue . . .
Step 2: Processing Logic
Using the pseudocode below, write the code that will meet the requirements.
Main Function
Declare the char variables for the 8 digits of the phone number
while true
Call the ReadDials function passing the 8 digits
by reference. ReadDials returns an error code by
value.
If the return value is -5, exit the do while loop
If the error code is -1, display the
error message "ERROR - An invalid character was entered".
If the error code is -2, display the
error message "ERROR - Phone number cannot begin with 0".
If the error code is -3, display the
error message "ERROR - Phone number cannot begin with 555".
If the error code is -4, display the
error message "ERROR - Hyphen is not in the correct position".
Otherwise, call the AcknowledgeCall function
End-While
ReadDials function
Input the first digit
If a Q was entered, return -5.
Input the rest of the phone number
Call the ToDigit function for each of the 7 digits
not for digit 4
If ToDigit returns -1, return -1
If digit 4 is not a hyphen, return -4.
If digit 1 is 0, return -2.
If digits 1 - 3 are 5, return -3
Otherwise, return 0
ToDigit function
Convert the digit to upper case
Use a switch statement to determine if the digit is valid
and convert the letters to digits
If the digit is invalid, return -1.
If the digit is valid, return 0.
AcknowledgeCall function
Display the Phone Number.
A user will input an 8-place number, for example: 359-3177 (note that the hyphen is considered a digit).
The rules for entering phone numbers follow.
• 8 places
• It may have numbers, letters, or both.
• The phone number cannot begin with 555.
• The phone number cannot begin with 0 or 1.
• The hyphen must be in the 4th position.
• No other characters (@#$%^&*()_+=\|/><etc.) are allowed.
• If a letter is entered, its output will be a number (check your phone pad).
• Enter Q to Quit.
If all of the rules are met, you will output a message to the console that reads like the following.
Phone Number Dialed: UN9-3177 *the number entered
If all of the rules are not met, then you output one of the following error messages to the console.
• ERROR - Phone number cannot begin with 555
• ERROR - Phone number cannot begin with 0
• ERROR - Hyphen is not in the correct position
• ERROR - An invalid character was entered
It will then prompt the user to try again.
---More---
Step 1: Requirements: Phone-Dialing Program
Write a program that simulates the dialing of a phone number.
A user will input an 8-place number, for example: 359-3177 (note that the hyphen is considered a digit).
The rules for entering phone numbers follow.
• 8 places
• It may have numbers, letters, or both.
• The phone number cannot begin with 555.
• The phone number cannot begin with 0 or 1.
• The hyphen must be in the 4th position.
• No other characters (@#$%^&*()_+=\|/><etc.) are allowed.
• If a letter is entered, its output will be a number (check your phone pad).
• Enter Q to Quit.
If all of the rules are met, you will output a message to the console that reads like the following.
Phone Number Dialed: UN9-3177 *the number entered
If all of the rules are not met, then you output one of the following error messages to the console.
• ERROR - Phone number cannot begin with 555
• ERROR - Phone number cannot begin with 0
• ERROR - Hyphen is not in the correct position
• ERROR - An invalid character was entered
It will then prompt the user to try again.
This should be a lot of fun!
Here are some great things to think about as you begin your program!
Define a function named ReadDials() that reads each digit and letter dialed into 8 separate char variables (DO NOT USE ARRAYS). All the digits are sent back through parameters by reference.
Then, for each digit, the program will use a function named ToDigit(), which receives a single char argument (pass by reference) that may be a number or a letter of one of the digits dialed.
If it is a number, then return 0 by value indicating that it is a valid digit. If the digit is a letter, then the number corresponding to the letter is returned by reference, and return 0 by value indicating that it is a valid digit. Here are the letters associated with each digit.
2;A B C
3;D E F
4;G H I
5 ;J K L
6 ;M N O
7; P Q R S
8; T U V
9; W X Y Z
If the digit entered is not one of the valid digits or one of the valid letters, return –1 by value indicating that you have an invalid digit.
A phone number never begins with a 0, so the program should flag an error if such a number is entered. Make ReadDials() return –2 in this case.
A phone number never begins with 555, so the program should flag an error if such a number is entered. Make ReadDials() return –3 in this case.
A phone number always has a hyphen (-) in the 4th position. Make ReadDials() return –4 in this case (if it doesn't have a hyphen in the 4th position). If a hyphen is in any other position, it is considered an invalid digit.
If the phone number is valid, the main calls the AcknowledgeCall function to write the converted number to the output file.
All the logic of the program should be put in functions that are called from Main(): ReadDials() and AcknowledgeCall().
The ToDigits() function is called from the ReadDials() function and is used to convert each letter entered individually into a digit and to verify that the user has entered a valid phone number. Have the program work for any number of phone numbers.
In the ToDigits() function uses the toupper function to convert any letters entered to uppercase. All the error messages are to be written to the output file from main() based on the return value from the functions.
Continue processing until the user enters a Q.
You will set up the 8 char variables to hold the digits of the phone number in main() and pass the variables to the functions by reference.
Sample Output from the Program
Enter a phone number (Q to quit): 213-2121
Phone Number Dialed: 213-2121
Enter a phone number (Q to quit): asc-dfer
Phone Number Dialed: 272-3337
Enter a phone number (Q to quit): 555-resw
ERROR - Phone number cannot begin with 555
Enter a phone number (Q to quit): 098-8765
ERROR - Phone number cannot begin with 0
Enter a phone number (Q to quit): 12345678
ERROR - Hyphen is not in the correct position
Enter a phone number (Q to quit): @34-*uyt
ERROR - An invalid character was entered
Enter a phone number (Q to quit): Q
Press any key to continue . . .
Step 2: Processing Logic
Using the pseudocode below, write the code that will meet the requirements.
Main Function
Declare the char variables for the 8 digits of the phone number
while true
Call the ReadDials function passing the 8 digits
by reference. ReadDials returns an error code by
value.
If the return value is -5, exit the do while loop
If the error code is -1, display the
error message "ERROR - An invalid character was entered".
If the error code is -2, display the
error message "ERROR - Phone number cannot begin with 0".
If the error code is -3, display the
error message "ERROR - Phone number cannot begin with 555".
If the error code is -4, display the
error message "ERROR - Hyphen is not in the correct position".
Otherwise, call the AcknowledgeCall function
End-While
ReadDials function
Input the first digit
If a Q was entered, return -5.
Input the rest of the phone number
Call the ToDigit function for each of the 7 digits
not for digit 4
If ToDigit returns -1, return -1
If digit 4 is not a hyphen, return -4.
If digit 1 is 0, return -2.
If digits 1 - 3 are 5, return -3
Otherwise, return 0
ToDigit function
Convert the digit to upper case
Use a switch statement to determine if the digit is valid
and convert the letters to digits
If the digit is invalid, return -1.
If the digit is valid, return 0.
AcknowledgeCall function
Display the Phone Number.
Last edited on
| Then, for each digit, the program will use a function named ToDigit(), which receives a single char argument (pass by reference) that may be a number or a letter of one of the digits dialed. |
It sounds like they want ToDigit to handle just one character at a time. So you'd call the function for each of the 7 non-hyphen digits one at a time, sending d1 etc. by reference, and performing the checks on that d1 character - you don't need to create a new local variable d in ToDigit - you want function to act on whatever existing variable you pass in.
I'm sorry if this is a really dumb question, but I'm not quite gathering how to pass them to the toDigit one by one. How would I do this?
I imagine there would need to be a loop, but my efforts aren't working.
Is that why my code program won't even recognize when I enter a number in the fourth place holder or a 555 for the first three numbers?
I altered my code a bit in an attempt to make it work, if you can, please give me an example of how to make a loop in order to make the function work.
I imagine there would need to be a loop, but my efforts aren't working.
Is that why my code program won't even recognize when I enter a number in the fourth place holder or a 555 for the first three numbers?
I altered my code a bit in an attempt to make it work, if you can, please give me an example of how to make a loop in order to make the function work.
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I played around a bit with this. I have an if statement checking that each of the digits is valid, not using a loop. Seems to work OK so far, but maybe someone else has another creative solution. I know they don't want you to use an array.
Your 555 check isn't working because with a char you need to check for '5' not just 5. The assignments in the conversion of letters to numbers also need to have the number in single quotes.
I spaced out the cases in the toDigits just to make sure everything was there. It looks like you're missing case '9'. Edit: and you need to return 0 if the digit is valid.
Your 555 check isn't working because with a char you need to check for '5' not just 5. The assignments in the conversion of letters to numbers also need to have the number in single quotes.
I spaced out the cases in the toDigits just to make sure everything was there. It looks like you're missing case '9'. Edit: and you need to return 0 if the digit is valid.
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Thank you very much for your help! I think I've managed to figure out most of what had me confused, and your code was very clear and easy to understand. I'll have to work on that!
Once again, I appreciate your assistance and willingness to go above and beyond while answering the questions. I hadn't expected you to go and write the whole code!
A quick last question if you don't mind, when you set the variables inside the functions to (char, char, char) or (char&, char&, char&), why does it allow you to do this without variable names?
Also, why does the acknowledgeCall function not require the & symbols? Are they not being referenced to?
Hope these questions aren't too dumb. I'd just like to know for future reference.
Once again, I appreciate your assistance and willingness to go above and beyond while answering the questions. I hadn't expected you to go and write the whole code!
A quick last question if you don't mind, when you set the variables inside the functions to (char, char, char) or (char&, char&, char&), why does it allow you to do this without variable names?
Also, why does the acknowledgeCall function not require the & symbols? Are they not being referenced to?
Hope these questions aren't too dumb. I'd just like to know for future reference.
| when you set the variables inside the functions to (char, char, char) or (char&, char&, char&), why does it allow you to do this without variable names? |
With the function prototype declaration, you just need to tell the compiler the return type of the function, the name of the function, and the number and type of parameters. You don't need to include the parameter names - the compiler will just ignore them at that point.
| Also, why does the acknowledgeCall function not require the & symbols? Are they not being referenced to? |
The acknowledgeCall function just prints out the values of the variables. The function has no need to change the original value, so by the principle of least privilege, you don't need to give it that access - you can just pass the variables by value, not by reference. The other functions, ReadDials and toDigit, do change the value of the variable passed to them, so the variables do need to be passed by reference there.
Passing by reference - rd1 is sent to toDigit function
if (toDigit(rd1) == 0int toDigit(char& td)toDigit function sees the & operator and knows not to create a new memory location for a local variable td, but to consider td an alias, or just another name of, the original variable rd1 (which in turn is another name for d1 in main function).
So any change to td is actually a change to the original d1 variable.
case 'Z': td = '9';
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That's very cool! Thank you for explaining to me! I'm pretty certain I understand it now.
Just in case, I'm going to repeat what you said in my own words.
So, the value of the entries is between each function, and the names are all temporary. But, when the value is changed they have to pass by reference so that the value changes when it returns?
The & operator allows the function to know it doesn't need a new memory location and that it is considered a temporary name?
And lastly, all changes of value made are made to the variables entered originally, therefore replacing their original values?
Just in case, I'm going to repeat what you said in my own words.
So, the value of the entries is between each function, and the names are all temporary. But, when the value is changed they have to pass by reference so that the value changes when it returns?
The & operator allows the function to know it doesn't need a new memory location and that it is considered a temporary name?
And lastly, all changes of value made are made to the variables entered originally, therefore replacing their original values?
I think you have it. If you send parameters by reference - you're not creating new variables in the called function - you're creating an alias to the variable in the calling function. If you send parameters by value - you're creating variables in the called function which get a copy of the value from the calling function.
Here's a short example.
Here's a short example.
Pass by value - original value is not modified. The function gets a copy of number to work with but it has no access to change number in the main function. |
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5 5 |
Pass by reference - original value is modified. x in this case is just another name for number, so the variable in main is changed. |
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Oh, that example is great! It makes it easier to put the image in my head.
This made perfect sense upon looking at the examples, of course, without your explanation I wouldn't have gotten it at all.
Thank you, thank you, thank you so much!
This made perfect sense upon looking at the examples, of course, without your explanation I wouldn't have gotten it at all.
Thank you, thank you, thank you so much!
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