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I'm studying program verification and came across the following triple:
$$ \{\top\} \;P \; \{y=(x+1)\} $$ What's the meaning of the $\top$ symbol on the precondition? Does it mean $P$ can take any input?

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The symbol $\top$, known as top, stands for "True". There is also a symbol $\bot$, known as bottom, which stands for "False". Top is always true, and bottom is always false. In your case, having a precondition that always holds is the same as having no precondition.

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  • $\begingroup$ To be pedantic, I will point out that the meaning of "top" and "bottom" depends on the specific logical system - and maybe some other contexts ;) $\endgroup$ – gardenhead Nov 17 '16 at 21:34

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