A test question: What is the result of <code>(false - ~0)</code> Why <code>(false - ~0)</code> is <code>1</code>? On 32 bit machine <code>~0</code> is <code>11....11</code> where there are 32 <code>1</code> bits right? Then false to int conversion is <code>00....00</code> also 32 times, right? So we subtract from 32 <code>0</code> 32 <code>1</code>? Does it underflow and we get 1?

<code>0</code> is <code>int</code> → <code>~0</code> is <code>int</code> and equal <code>-1</code> → <code>false</code> gets promoted to <code>int</code>, which results in zero → your expression is calculated as <code>(0 - (-1))</code> which equals <code>1</code>.

(false - NOT (0)) is equal to 1?

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c++

A test question: What is the result of (false - ~0)

Why (false - ~0) is 1? On 32 bit machine ~0 is 11....11 where there are 32 1 bits right? Then false to int conversion is 00....00 also 32 times, right? So we subtract from 32 0 32 1? Does it underflow and we get 1?

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asked Dec 01 '22 15:12

Narek

1 Answers

0 is int → ~0 is int and equal -1 → false gets promoted to int, which results in zero → your expression is calculated as (0 - (-1)) which equals 1.