CODEWITHSUNDEEP
cloopsdo-whilepost-increment
user1329320
user1329320

Reputation: 11

C postincrement in condition

do {instructions...}
while (x--)

should first do the instructions, then check if x is not 0 and go on/or leave the loop according to result and only after all these operations decrement x.

But my compiler decrements first.

Who is wrong? Me or my compiler ;-)? Could You please explain me why?

Upvotes: 1

Views: 152

Answers (3)

pmg
pmg

Reputation: 108978

Many expressions in C have a value and a side-effect.

For the expression x-- the value is the value x had before; and the side-effect is decrementing x's value.

So, if you start with x being 1, when the execution reaches that expression, it will yield the value 1 and set x to 0. The next time the expression is evaluated, the value is 0 and x is set to -1, ...

Upvotes: 3

nims
nims

Reputation: 3871

What You are saying

should first do the instructions, then check if 'x' is not '0' and go on/or leave the loop according to result AND ONLY AFTER ALL THESE OPERATIONS DECREMENT 'x'

What should be

should first do the instructions, then check if 'x' is not '0', then DECREMENT 'x' and go on/or leave the loop according to result

Upvotes: 3

user520288
user520288

Reputation:

the flow is :

1) do instructions

2) check value of x

3.1) is x == 0? then do x-- (x becomes -1) and exit the loop

3.2) is x != 0? then do x-- and go to step 1)

Upvotes: 1

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