How to express ln2 in C language

The methods of expressing ln2 in C language are: using the standard library function log, using the symbolic constant M_LN2, using the compiler's built-in preprocessing macro, using the approximate value 0.69314718056

The C language represents ln2

The C language represents the natural logarithm of the base e of the natural logarithm, that is, ln2, in the following ways:

1. Use standard library functions

<code class="c">#include <math.h>

double ln2 = log(2.0);</code>

2. Use symbolic constants

The C99 standard introduces the symbolic constant M_LN2, which represents the approximate value of ln2:

<code class="c">#include <math.h>

double ln2 = M_LN2;</code>

3. Use the compiler’s built-in preprocessing macros

Some compilers provide built-in preprocessing macros to represent ln2, for example:

• GCC: __log2
• Clang: log2

When using these macros, you need to specify the appropriate macro definition in the compile command , for example:

<code>gcc -D__log2=log2</code>

4. Using approximations

The following approximations can be used to represent ln2:

<code>ln2 ≈ 0.69314718056</code>

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