Call to undefined function pi()

Question

I am using Borland C++Builder 3.

I have included math.h in my code.

When using this code:

float b;   
b=pi();

I get the following compiler error:

call to undefined function pi()

`math.h` has no `pi()` in it. – HolyBlackCat Jan 25 '18 at 19:12 — HolyBlackCat, Jan 25 '18 at 19:12
Use `double` instead of `float`. – i486 Jan 25 '18 at 19:46 — i486, Jan 25 '18 at 19:46
@i486 -- that won't affect the problem. – Pete Becker Jan 25 '18 at 19:47 — Pete Becker, Jan 25 '18 at 19:47
@PeteBecker For that reason it is comment, not answer. – i486 Jan 25 '18 at 21:25 — i486, Jan 25 '18 at 21:25

score 1 · Answer 1 · edited Jan 25 '18 at 19:18

1

Use the M_PI constant, not the pi() function.

edited Jan 25 '18 at 19:18

Remy Lebeau

answered Jan 25 '18 at 19:12

cptwonton

There is no `M_PI` in the C++ standard. – lisyarus Jan 25 '18 at 19:20
2

@lisyarus: true, but `math.h` is not a C++ header to begin with, it is C header, and `M_PI` is defined in `math.h` nonetheless, in many C/C++ compilers including Borland's. It is a common extension, if not standardized – Remy Lebeau Jan 25 '18 at 19:22
2

@RemyLebeau True, but the question in tagged with `c++`. Anyways, `M_PI` is not part of the C standard either. I believe that an explanation of what `M_PI` actually is (probably with a link that François Andrieux have posted) is needed here, not just "use M_PI". – lisyarus Jan 25 '18 at 19:28
1

@lisyarus: it is also tagged with `c++builder` and `c++builder-3`, and these do define `M_PI`. So for a question tagged with these tags, the answer is right and does not need any extra explanation. It is a simple constant with a well known value, after all. – Rudy Velthuis Jan 30 '18 at 21:08

1 Answers1