Lets say I have 4 intiger variables
int a =1;
int b =2
int c =0;
int d =0;
I want to find out the simplest way to join them into the string that I end up with
"12:00"
I managed to do it but I don't think I did it in the most optimal way.
I will not disclose how I did it , so you can keep an open mind
It depends. Are any of those variables going to be greater than 9 or less than 0? If not it can be really simple:
char foo[6];
.
.
.
foo[0] = a + '0';
foo[1] = b + '0';
foo[2] = ':';
foo[3] = c + '0';
foo[4] = d + '0';
foo[5] = '\0';
what does
+'0'
do?
My way was to use charAt
String s = (String) a + b + ":" + c + d;
to avoid a XY_problem ... please explain what you really want to achieve.
I managed to do it but I don't think I did it in the most optimal way.
In 99% it's not necessary anyway.
Lets say you have 4 integer variables
Why do you want to join them together in a string (a null terminated array of chars, aka a C string), or do you mean a String (an object created by the String library) ? They are not the same thing
Hello,
int a,b,c,d;
void loop() {
char text[10];
sprintf(text,"%02d:%02d",10*a+b,10*c+d);
}
The advantage of the code above is that you do not use C++ but C.
C is faster on a microcontroller and smaller in footprint in may cases.
You can also leave out the 02 format specifier if you want 1:00 instead of 01:00.
Best Regards,
Johi
The advantage of the code above is that you do not use C++ but C.
C is faster on a microcontroller and smaller in footprint in may cases.
Can you force the compiler to use C rather than C++ ?
Why bother with multiplication ?
sprintf(text, "%d%d:%d%d", a, b, c, d);
As this question doesn't make so much sense for me anyway, yeah - let's use sprintf on the AVR.
#define VERSION 4
// V PRGOGMEM globals
// 0 2380 196
// 1 3932 204
// 2 3632 202
// 3 3614 202
// 4 2112 192
int a, b, c, d;
void setup() {
Serial.begin(115200);
a = random(0, 3);
b = random (0, 10);
c = random (0, 6);
b = random (0, 10);
#if VERSION == 0
Serial.print(a);
Serial.print(b);
Serial.print(":");
Serial.print(c);
Serial.print(d);
#elif VERSION == 1
String s = (String) a + b + ":" + c + d;
Serial.print(s);
#elif VERSION == 2
char text[10];
sprintf(text, "%02d:%02d", 10 * a + b, 10 * c + d);
Serial.print(text);
#elif VERSION == 3
char text[10];
sprintf(text, "%d%d:%d%d", a, b, c, d);
Serial.print(text);
#elif VERSION == 4
char text[6];
text[0] = a + 0x30;
text[1] = b + 0x30;
text[2] = ':';
text[3] = c + 0x30;
text[4] = d + 0x30;
text[5] = '\0';
Serial.print(text);
#endif
}
void loop() {
}
"if this is the solution - I want my problem back"
JOHI:
The advantage of the code above is that you do not use C++ but C.
C is faster on a microcontroller and smaller in footprint in may cases.
I highly doubt that in the case of GCC, at least as a generalization. Probably other compilers too. I would expect a noticeable difference only with advanced OO like polymorphism, etc. Certainly the use of a class like String to perform otherwise simple manipulations will add overhead. Perhaps that is what you actually meant, C utility functions vs. C++ class methods?
Your statement sort of suggests that all C++ features add overhead, I think not. Perhaps that was not your intention, but it's best to avoid misunderstanding. I think many "plain vanilla" C features that were imported with minor changes, into C++, don't add any overhead, execution or memory footprint.
The choice to use, or not use, C++ classes in C++ is indeed an important aspect to consider when the target machine is relatively small and relatively slow.