How to use question mark expression in C language
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Question mark expression in C language
Question mark expression
(expression 1)? (expression 2): (expression 3)
Execute expression 2 if expression 1 is valid, otherwise execute expression 3
Give an example
Inta=5,b=3
Printf ("% d", a > btincaVlb)
Run
Execute if an is greater than b: the preceding one outputs a. Otherwise execute: the output b is followed by. In this case, the output is 5.
Points for attention
The question mark expression runs from right to left
For example
Inta=8,b=3,c=7
Printf ("d", a > Bevera > c?a:c:b > c?b:c)
It can be done in three steps.
Step 1: B > c?b:c result is c
Step 2: a > c?a:c result is a
Step 3: the results of the first two steps correspond to expression 3 and expression 2, namely a > b?a:c
The final output is an or 8
Question mark expression and comma expression
Question mark expression:
# include
Voidmain ()
{
Inta,b,c,d,e
Cedar 9
Dumb8
Scanf ("% djas% d", & a djm% d)
E = (a > b)? CRAV d
Printf ("% d\ n", e)
}
It can be understood that the whole expression after "=" can be regarded as (expression 1). If a > b, then eDec, otherwise eDead. (expression 2): (expression 3)
Comma expression:
# include
Voidmain ()
{
Inta,b,c,d,e
Cedar 9
Dumb8
Scanf ("% djas% d", & a djm% d)
E = ((a=b+c), aqd)
Printf ("% d\ n", e)
}
Make a small change based on the question mark expression to get:
The comma expression has the lowest precedence, e = ((a=b+c), aqd) first evaluates the bdistribuc assignment to a, and then evaluates the ACDD assignment to e; this is the simplest comma expression, and you can continue to add "," after ACDD.
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