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predicate_logic [2015/10/13 20:56] nikolaj |
predicate_logic [2016/05/01 15:56] nikolaj |
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| the first time, which we use to introduce new notation. | the first time, which we use to introduce new notation. | ||
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| + | I came up with | ||
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| + | $\phi(!a) \equiv \phi(a) \land \forall x.\left(\phi(x)\implies x=a\right)$ | ||
| + | |||
| + | for a predicate $P$, expressing that $P$ only holds for the term $a$. Then | ||
| + | |||
| + | $\exists! x.\,\phi(x) \equiv \exists x.\,\phi(!x)$ | ||
| We also use the abbreviation | We also use the abbreviation | ||
