I/if keyword



I <condition>
   ...





I <condition>
   ...
E
   ...



I <condition1>
   ...
E I <condition2>
   ...



I <condition1>
   ...
E I <condition2>
   ...
E
   ...

Two consecutive keywords 
E
/
else
and 
I
/
if
are treated especially, so there is no need for a separate/additional keyword like 
elif
in Python or 
elsif
 in Ruby.

Also 
I
/
if
and 
E
/
else
can be used in expressions similarly to ternary operator 
?:
from C:
sign = I x < 0 {-1} E I x > 0 {1} E 0 // 11l

sign =  x < 0 ? -1  :  x > 0 ? 1 : 0; // C


I/if subkeywords



I.unlikely <condition>
   ...
is used as a sign to the compiler that condition in most of the cases will be false.

This affects the generation of machine code as follows:
  1. The body of the 
    I
    /
    if
    statement is moved to a separate (“cold”) area of ​​the code segment or to the end of the function after all the “hot” code.
  2. If the body of the 
    I
    /
    if
    statement consists of a single function call, then that call is not inlined.
    Example:
  3. The space on the stack for local variables inside the body of the 
    I
    /
    if
    statement is allocated not at the ‘beginning of the function’/‘moment of entry into the function’, but at the beginning of the body of the 
    I
    /
    if
    statement itself.
    Example:
     

I.likely <condition>
   ...
is used as a sign to the compiler that condition in most of the cases will be true.

Affects the generation of machine code only if there is an 
E
/
else
branch, the code in which is marked "unlikely".