Integer arithmetic

Newbie
1

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ROOT Version: 6.36.06
Platform: Mac OSX
Compiler: Not Provided

I am getting different results depending on whether I load some code that contains a a function or just simply code to be executed. Here is the file

int test() { // comment out this line for second example
  double xLo = 0.0;
  double xHi = 1.0;
  int nBins=10;
  double delta = (xHi - xLo) / nBins;
  for (int iBin = 0; iBin < nBins; iBin++) {
    double x = iBin * delta;
    std::cout << iBin << " " << x << " " << delta << " " << iBin * delta <<  std::endl;
  }
  return 1;
} //comment out this line for second example

loading and executing this code gives the expected result:


root [0] .L test.cc
root [1] test()
0 0 0.1 0
1 0.1 0.1 0.1
2 0.2 0.1 0.2
3 0.3 0.1 0.3
4 0.4 0.1 0.4
5 0.5 0.1 0.5
6 0.6 0.1 0.6
7 0.7 0.1 0.7
8 0.8 0.1 0.8
9 0.9 0.1 0.9
(int) 1

However, if I comment out the two lines declaring and ending the function I get a different result in which either integer arithmetic is done instead of double:


root [0] .L test.cc
0 0 0.1 0
1 0 0.1 0.1
2 0 0.1 0.2
3 0 0.1 0.3
4 0 0.1 0.4
5 0 0.1 0.5
6 0 0.1 0.6
7 0 0.1 0.7
8 0 0.1 0.8
9 0 0.1 0.9

My root details:


   ------------------------------------------------------------------
  | Welcome to ROOT 6.36.04                        https://root.cern |
  | (c) 1995-2025, The ROOT Team; conception: R. Brun, F. Rademakers |
  | Built for macosxarm64 on Sep 17 2025, 18:52:01                   |
  | From tags/6-36-04@6-36-04                                        |
  | With Apple clang version 17.0.0 (clang-1700.3.19.1)              |
  | Try '.help'/'.?', '.demo', '.license', '.credits', '.quit'/'.q'  |
   ------------------------------------------------------------------
2

I cannot reproduce the issue, I obtain the same result for both version… Maybe it’s an issue with MacOS? maybe @couet can give it a try

3

@bellenot On a Linux (x86_64) machine, when trying the test.cc example with “commented lines”, ROOT 6.36.04 and 6.34.10 show the same problem as reported. ROOT 6.32.18 dies with a segmentation violation. ROOT 6.30.08 and older (e.g., 6.28.12) report and “error: expected unqualified-id” (for the “for” loop).

@preimer It seems to me that you are trying to create/use a so-called “unnamed macro”.
In this case, you need to “encapsulate” the whole source code in a {...} block.
So, in your test.cc example, replace the line:
int test() {
With a simple line:
{
I also recall that many older ROOT versions required the very first line of an “unnamed macro” file to be the “{” line (so, do not add any “comment lines”, or any preprocessor directives, right in the beginning of your macro file; add them after the initial “{” line, if needed).
Be also aware that there are known problems with “unnamed macros” in ROOT 6, e.g., the “return” from it is broken (reported in 2018, still unsolved in 2025).

4

Interesting… Thanks for trying! Can one of you open a GitHub issue for this?

5

Maybe related:

https://its.cern.ch/jira/browse/ROOT-7033

For the unnamed macro - return behavior, it slipped through the cracks, I opened now:

6

Yes, enclosing the code

{
  double xLo = 0.0;
  double xHi = 1.0;
  int nBins=10;
  double delta = (xHi - xLo) / nBins;
  for (int iBin = 0; iBin < nBins; iBin++) {
    double x = iBin * delta;
    std::cout << iBin << " " << x << " " << delta << " " << iBin * delta <<  std::endl;
  }
  return 1;
}

Works as expected on my MacBook.