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Re: [mizar] question about translating to logical connectives



Hi Brando,

On Tue, 27 Nov 2018, Miranda, Brando wrote:

This is my first time using the forum mailing list. Hope to learn to use it well! If there is a guidance of sort of questions that are appropriate feel free to share it with me, Especially for really basic questions? :)

I was trying to do exercise exercise 1.3.1 of https://www.cs.ru.nl/~freek/mizar/mizman.ps.gz 9 easy steps of Mizar. I tried translating

phi iff not not phi

and put it in mizar and mizar threw me some errors:

:: example of a comment
environ
 vocabularies MY_MIZAR;
begin
phi implies not not psi & not not psi implies phi;
::>*321
::>
::> 321: Predicate symbol or "is" expected

I put after the environ begin clause but throws an error that isn’t too helpful. How can I check if what I am doing in that exercise I am doing correctly?

The error marker points to the 'phi' symbol and the corresponding error message indicates that this 'phi' is not understood as a valid predicate symbol. Section 1.3.2 of the tutorial provides a few examples of basic predicates which can be imported from the library and used to build formulae.

I guess that Freek intended this kind of exercise to be "contemplated" rather than directly checked with Mizar.

Best,

Adam

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