format for double for printf

[RoS]

the format for conversion of double in the function printf is
"%f" or "%lf" or both?

for example
printf("%f", (double)0.0);
printf("%lf", (double)0.0);
are both ok?

Good morning
Thank you

 

[Thomas X. Iverson]

it seems like that in c there is no need to print a double varible
with %lf format
%f is ok
but for long interger , u should use %ld

 

[Ian Collins]

the format for conversion of double in the function printf is
"%f" or "%lf" or both?

for example
printf("%f", (double)0.0);
printf("%lf", (double)0.0);
are both ok?

Yes they are equivalent, the l modifier has no effect for the f specifier.

 

[pete]

Yes they are equivalent,
the l modifier has no effect for the f specifier.

That's the case for C99.
For C89,
a function call to printf is undefined
if "%lf" is the first argument.

 

[vippstar]

That's the case for C99.
For C89,
a function call to printf is undefined
if "%lf" is the first argument.

The first? "%d %lf" is not undefined?

 

[Keith Thompson]

The first? "%d %lf" is not undefined?

Yes, "%d %lf" is undefined for C89/C90's printf. He said "if", not
"if and only if".

(Incidentally, given printf("%d %lf", x, y), the first *argument*
isn't %d; it's the string "%d %ld".)

 

[Walter Roberson]

That's the case for C99.
For C89,
a function call to printf is undefined
if "%lf" is the first argument.

And just to confuse matters, in C89, "%Lf" *is* defined and
indicates that the corresponding argument is long double .