Of course, it works just fine on any AVR board. But with the compiler used for ESP32s one must code
Num=max(Num,(unt8_t)3); Seems like a bit of C++ rigor overreach to me.
Num=max(Num,3); throws compiler error if Num declared int8_t. Really?
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Re: Num=max(Num,3); throws compiler error if Num declared int8_t. Really?
I looked up the max function and it says the two values need to be the same type.
A constant 8 has a dats type of short. I imagine the data type of num is not.
The data type of an integer data type is determined by its value.
Tom
A constant 8 has a dats type of short. I imagine the data type of num is not.
The data type of an integer data type is determined by its value.
Tom
IT Professional, Maker
Santiago, Dominican Republic
Santiago, Dominican Republic
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Re: Num=max(Num,3); throws compiler error if Num declared int8_t. Really?
I saw that, and I'm wondering what the value of such rigor would be. Curiously, Num=max(Num-1,4) compiles just fine. I suppose the arithmetic forces the data types to be sorted out automatically.
I've never heard of a "dats" type, and the C++ reference doesn't mention it anywhere that I could find.
The Arduino reference is a little more generous:
"Parameters
x: the first number. Allowed data types: any data type.
y: the second number. Allowed data types: any data type."
And, yes, I know that Arduino C is not a "real" C++ language, but it certainly has its utility for the purpose. Thanks for your insights...Jack
I've never heard of a "dats" type, and the C++ reference doesn't mention it anywhere that I could find.
The Arduino reference is a little more generous:
"Parameters
x: the first number. Allowed data types: any data type.
y: the second number. Allowed data types: any data type."
And, yes, I know that Arduino C is not a "real" C++ language, but it certainly has its utility for the purpose. Thanks for your insights...Jack
Re: Num=max(Num,3); throws compiler error if Num declared int8_t. Really?
I am traveling and without my dev software. Or, I would check this: what is the data type of Num - 1
When num is small and when large. I suspect they are different.
So Max has a to be defined data type and a defined data type to compare.
Max(num - 1, num - 3) should fail too.
In the original it has both data types (different) and refuses to convert for comparison.
This will give us a glimpse into the compiler logic for code generation or more.
Tom
(It is bad form to ridicule someone, giving free help, for a typo.)
When num is small and when large. I suspect they are different.
So Max has a to be defined data type and a defined data type to compare.
Max(num - 1, num - 3) should fail too.
In the original it has both data types (different) and refuses to convert for comparison.
This will give us a glimpse into the compiler logic for code generation or more.
Tom
(It is bad form to ridicule someone, giving free help, for a typo.)
IT Professional, Maker
Santiago, Dominican Republic
Santiago, Dominican Republic
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Re: Num=max(Num,3); throws compiler error if Num declared int8_t. Really?
First of all, please be aware that I thought the word "dats" was actually a legitimate word somewhere in the C++ language, one that I did not know anything about. I did, indeed, try to find a reference to it. My statement wasn't meant to be a criticism at all. Sorry for the confusion, and sorry to be clueless on seeing that it was a simple typo.
As for what works and doesn't work when compiling, I wrote the following code:
All of the lines commented out throw a compiler error when compiling for an ESP32, for the reasons you described above, and all work fine for an AVR. Interesting that the template process allows int32_t to sneak in and work OK for an ESP32.
I went down this bunny hole after reading another post in this forum about arithmetic that uses int variables taking longer to execute than arithmetic using int16_t or int32_t variables. I had a piece of code where efficiency was important, and I converted some int declarations to int16_t, and the fun began.
And I fully recognize that the AVR compiler operates at a level of abstraction targeted to makers wanting to blink LEDs, read sensors and move servos, and that a professional software engineer writing critical firmware for an ESP32 has different needs and expectations about C++ rigor.
As for what works and doesn't work when compiling, I wrote the following code:
Code: Select all
template <typename T>
inline T const& Max (T const& a, T const& b) {
return a < b ? b : a;
}
void setup() {
Serial.begin(115200);
delay(1000);
int NumAs_int = 5;
long int NumAs_long_int = 5;
int8_t NumAs_int8_t = 5;
int16_t NumAs_int16_t = 5;
int32_t NumAs_int32_t = 5;
NumAs_int = max(NumAs_int, 6);
// NumAs_long_int = max(NumAs_long_int, 6);
// NumAs_int8_t = max(NumAs_int8_t, 6);
// NumAs_int16_t = max(NumAs_int16_t, 6);
// NumAs_int32_t = max(NumAs_int32_t, 6);
NumAs_int = Max(NumAs_int, 6);
// NumAs_long_int = Max(NumAs_long_int, 6);
// NumAs_int8_t = Max(NumAs_int8_t, 6);
// NumAs_int16_t = Max(NumAs_int16_t, 6);
NumAs_int32_t = Max(NumAs_int32_t, 6);
Serial.print("NumAs_int: "); Serial.println(NumAs_int);
Serial.print("NumAs_long_int: "); Serial.println(NumAs_long_int);
Serial.print("NumAs_int8_t: "); Serial.println(NumAs_int8_t);
Serial.print("NumAs_int16_t: "); Serial.println(NumAs_int16_t);
Serial.print("NumAs_int32_t: "); Serial.println(NumAs_int32_t);
}
void loop() {
}
I went down this bunny hole after reading another post in this forum about arithmetic that uses int variables taking longer to execute than arithmetic using int16_t or int32_t variables. I had a piece of code where efficiency was important, and I converted some int declarations to int16_t, and the fun began.
And I fully recognize that the AVR compiler operates at a level of abstraction targeted to makers wanting to blink LEDs, read sensors and move servos, and that a professional software engineer writing critical firmware for an ESP32 has different needs and expectations about C++ rigor.
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