Excess elements in scalar initializer

[faca87]

Hello, i’ve this macro to produce root files from raw data.
If I set

double delay[Nadc]= {0, 4.0720e4, 0, 4.0720e4};

but if I set the if conditions

 if ((strcmp(month, "JuneOctober22") == 0) ) delay[Nadc] = {0, 4.0720e4, 0, 4.0720e4};   // June2022 and October2022 delay
  else if ((strcmp(month, "February23") == 0)) delay[Nadc] = {0, 4.0270e4, 0, 4.0270e4};   //February 2023 delay

I get this error

maketree.cpp:102:61: error: excess elements in scalar initializer
  if ((strcmp(month, "JuneOctober22") == 0) ) delay[Nadc] = {0, 4.0720e4, 0, 4.0720e4};   // June2022 and October2022 delay
                                                            ^ ~~~~~~~~~~~~~~~~~~~~~~~~
maketree.cpp:103:62: error: excess elements in scalar initializer
  else if ((strcmp(month, "February23") == 0)) delay[Nadc] = {0, 4.0270e4, 0, 4.0270e4};   //February 2023 delay

maketree.cpp (8.0 KB)

[jalopezg]

Hi @faca87,

@faca87

but if I set the if conditions

 if ((strcmp(month, "JuneOctober22") == 0) ) delay[Nadc] = {0, 4.0720e4, 0, 4.0720e4};   // June2022 and October2022 delay
  else if ((strcmp(month, "February23") == 0)) delay[Nadc] = {0, 4.0270e4, 0, 4.0270e4};   //February 2023 delay

It seems that delay has been declared as an array of Nadc elements. Thus, the type of delay[i], being i an integer used to subscript the array, is a double.
However, you are trying to assign a std::initializer_list, i.e. a list of values, to one of such elements in the array, which of course is ill-formed.

I guess you instead intended to replace all the elements in the array, as in delay = { ... }; nonetheless, C++ does not allow array assignment, so you have basically two options:

1. Declare delay as an std::array<double, Nadc>, which allows direct assignment, e.g.

std::array<double, 4> delay = {0, 4.0720e4, 0, 4.0720e4};
delay = {0, 4.0720e4, 0, 4.0720e4};

2. Copy-assign element by element, either manually or by using std::copy().

Cheers,
J.

[faca87]

Thank you @jalopezg it works!

But, why my macro worked when I didn’t have the if condition, but it didn’t work using the if?
Fausto

[jalopezg]

That’s weird, as in: it’s ill-formed C++ and I am pretty sure that every compliant compiler would complain. Are you absolutely sure that there were no more changes in the code?

Cheers,
J.

[faca87]

Yes, the if condition was the only change…indeed, before of your help, deleting the if, the code worked again!

[Wile_E_Coyote]

@jalopezg What’s “ill-formed” in:

const int Nadc = 4;
double delay[Nadc] = {0, 4.0720e4, 0, 4.0720e4}; // aggregate initialization

[jalopezg]

@faca87

Yes, the if condition was the only change…indeed, before of your help, deleting the if, the code worked again!

Sure. IIUC how your code looks before / after the change, before the change, the array is initialized and it is not assigned-to again. That is perfectly legal.

@Wile_E_Coyote

const int Nadc = 4;
double delay[Nadc] = {0, 4.0720e4, 0, 4.0720e4}; // aggregate initialization

@Wile_E_Coyote, nothing if the array is just initialized; I was actually referring to using copy-assignment after the delay[] array has been initialized (see above).

Cheers,
J.

[faca87]

thank you!