Converting Float to Char in C: Exploring the Use of sprintf

[ver_mathstats]

Homework Statement

We are required to write a function in C to take a float variable and return it as a char variable in a single byte.

Relevant Equations

float to char

I am very new to C programming so am struggling with this question and how exactly to begin it, when we are doing this are we to use something like sprintf?

Thank you.

 

[Mark44]

Homework Statement:: We are required to write a function in C to take a float variable and return it as a char variable in a single byte.
Relevant Equations:: float to char

I am very new to C programming so am struggling with this question and how exactly to begin it, when we are doing this are we to use something like sprintf?

No. The goal is not to print the character but to return it.
The problem is very simple, unless you have left out some additional requirement. All you need to do is to write a function with a float parameter, and return that parameter as a char.

A float is 32 bits, and a char is 8, so what the function will do is to truncate the fractional part of the float and attempt to store it in 8 bits, the size of a char.

 

[phinds]

Check out the concept of "type casting"

 

[ver_mathstats]

Check out the concept of "type casting"

Okay so after reading about type casting, we are to just cast float to int then int to char?

 

[Mark44]

Okay so after reading about type casting, we are to just cast float to int then int to char?

You don't need to do the cast in two steps: a cast from float to char will work. Also, you don't need to do an explicit cast (i.e., write an expression using a cast operator). If you do as I suggested in my earlier post, and return the float parameter, the code will implicitly cast the value to a char. The compiler will issue a warning though, so an explicit cast is better.

 

[Mark44]

Restating what I said earlier...

All you need to do is to write a function with a float parameter, and return that parameter as a char.

The compiler will likely generate a warning, but will produce code that will run.

 

[pbuk]

Perhaps it is worth mentioning that although 'char' clearly stands for 'character', this is a misleading historical accident: it is actually just an unsigned 8 bit integer.

 

[ver_mathstats]

Restating what I said earlier...
The compiler will likely generate a warning, but will produce code that will run.

I expected it to generate a warning, however my code will not run to begin with and am having difficultly proceeding further, and for some reason I am unable to show my code in this thread and what I have so far.

 

[Mark44]

I expected it to generate a warning, however my code will not run to begin with and am having difficultly proceeding further, and for some reason I am unable to show my code in this thread and what I have so far.

Show us what you have so far, and I'm sure we can steer you in the right direction. The function you're asked to write is extremely simple, with a one-line body.

Copy your code as text, not as an image, and put it inside a pair of code tags, like this:

[code=c]char convertToChar(float value) {
// Body of your function
}[/code]

The browser won't show the opening and closing code tags. I have modified the code tags shown above to keep the browser from consuming them, as it normally would do.

 

[ver_mathstats]

Show us what you have so far, and I'm sure we can steer you in the right direction. The function you're asked to write is extremely simple, with a one-line body.

Copy your code as text, not as an image, and put it inside a pair of code tags, like this:

[code=c]char convertToChar(float value) {
// Body of your function
}[/code]

The browser won't show the opening and closing code tags. I have modified the code tags shown above to keep the browser from consuming them, as it normally would do.

Yes I'm trying to show my code so far but I am still having issues even with copying and pasting as text and using the code tags. Still get this error message: "Oops! We ran into some problems. Please try again later. More error details may be in the browser console." I am hoping that the image works.

 

[pbuk]

Ah, this is a known bug: the forum will not accept the text "char(arg)" (except from me: I have special powers).

 

[pbuk]

One problem is that you are trying to use char as a function: instead you should write char result = <char>arg;. Another problem is that you are redefining arg as a variable when it is already defined as a parameter: delete the line float arg;.

 

[Mark44]

1. Change the name of the function -- toFloat() suggests that it's going to convert something to a float. That's not what the function should be doing.
2. Delete the first two lines of the function body.
3. Change the third line so that it returns the function's argument.

Like I said, all you need is a single line of code in the function body.

 

[pbuk]

3. Change the third line so that it returns the function's argument.

Like I said, all you need is a single line of code in the function body.

Yes, this is better than my solution - let the compiler do the work implicitly!

 

[ver_mathstats]

1. Change the name of the function -- toFloat() suggests that it's going to convert something to a float. That's not what the function should be doing.
2. Delete the first two lines of the function body.
3. Change the third line so that it returns the function's argument.

Like I said, all you need is a single line of code in the function body.

Thank you for the suggestions, they are all very helpful.

 

[Mark44]

Thank you for the suggestions, they are all very helpful.

But did you get something to work yet?

 

[ver_mathstats]

But did you get something to work yet?

Not quite, I am still trying with everyone's suggestions.

 

[pbuk]

Still a few problems there. Have a look at the comments below:

#include <stdio.h>

char toChar(float arg) {
  return arg;
}

int main() {
  // We need to save the return value so we can use it.  We
  // also need to choose a character code that will print:
  // capital letters start at 65 so this is a good choice.
  char character = toChar(65.999);
  // Note we can't see the value of arg here: it is not
  // "in scope".
  printf(
    "The character with the code %i is %c\n",
    character,
    character
  );
  return 0;
}

You can see this working at https://replit.com/@pbuk/CylindricalMajorSquares#main.cpp

 

[Mark44]

Not quite, I am still trying with everyone's suggestions.
View attachment 314925

This won't compile (syntax errors):

1. result in your function is not declared.
2. arg in main is not declared.

You also have a semantic error (a type of error that isn't due to improper use of the language, but nevertheless causes problems).
Your toChar() function is defined to return a char value, but you aren't using it. For any function that returns a non-void value, the call to the function should most often be on the right side of an assignment statement or as a value to be displayed via printf or anywhere else where a value is meant. Such a function should not be called like you have done; i.e., as toChar(5.33); .

If the syntax errors are fixed, when you compile and run the code, the function will calculate its value correctly, but the call to this function shown above will cause the value to be discarded.

 

[ver_mathstats]

Still a few problems there. Have a look at the comments below:

#include <stdio.h>

char toChar(float arg) {
  return arg;
}

int main() {
  // We need to save the return value so we can use it.  We
  // also need to choose a character code that will print:
  // capital letters start at 65 so this is a good choice.
  char character = toChar(65.999);
  // Note we can't see the value of arg here: it is not
  // "in scope".
  printf(
    "The character with the code %i is %c\n",
    character,
    character
  );
  return 0;
}

You can see this working at https://replit.com/@pbuk/CylindricalMajorSquares#main.cpp

I think I am mainly confused by the single line in the function and then what the purpose of having a function here is if it's only result arg, I think that's what was throwing me off

 

[Mark44]

I think I am mainly confused by the single line in the function and then what the purpose of having a function here is if it's only result arg,

The purpose of the function is to convert an input float argument to a char value, which is what you stated as the program requirement.

I am We are required to write a function in C to take a float variable and return it as a char variable in a single byte.

char toChar(float arg) {
  return arg;
}

arg is passed to the toChar function as a float, but when it is returned, it has to be demoted to an 8-bit quantity. This compiler generates code that does the actual conversion from a 32-bit float to an 8-bit char.

 

[ver_mathstats]

The purpose of the function is to convert an input float argument to a char value, which is what you stated as the program requirement.

char toChar(float arg) {
  return arg;
}

arg is passed to the toChar function as a float, but when it is returned, it has to be demoted to an 8-bit quantity. This compiler generates code that does the actual conversion from a 32-bit float to an 8-bit char.

I know that's the assignment question, but I just meant more so I wasn't expecting it to be just one line of code.