Question

有谁知道类似于

的引理在哪里

∃(x::real). a^x = (b::real)

可能会被发现？我在“查询”中找不到类似的内容，但它看起来非常方便。

Answer 1

您需要在a和b上做一些假设，并且您需要使用powr运算符而不是^，因为^仅适用于n n次幂powr是一个自然数。另一方面，lemma fixes a b :: real assumes "a > 0" "a ≠ 1" "b > 0" shows "∃x. a powr x = b" proof from assms show "a powr (log a b) = b" by simp qed是针对任何其他实数的任何非负实数。（或类似的复数）

(void)URLSession:(NSURLSession *)connection
//    task:(NSURLSessionTask *)task
    didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge
    completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential * __nullable credential))completionHandler
{
    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
    {
#if 1 && defined(DEBUG)
        NSLog (@"didReceiveChallenge: Using SSL");
#endif // DEBUG

        if ([challenge.protectionSpace.host isEqualToString:HOST])
        {
#if 1 && defined(DEBUG)
            NSLog (@"didReceiveChallenge: Using Protection Space Host - %@", HOST);
#endif // DEBUG

            [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
        }
        else
        {
            [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
        }
    }
    else

    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodHTTPBasic] ||
        [challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodHTTPDigest])
    {
#if 1 && defined(DEBUG)
        NSLog (@"didReceiveChallenge: (Basic / Digest) #%ld - user: %@, password: %@",
               (long)[challenge previousFailureCount],  USERNAME, PASSWORD);

#endif // DEBUG

        if ([challenge previousFailureCount] == 0)
        {
#if 1 && defined(DEBUG)
            NSLog (@"didReceiveChallenge: previousFailureCount == 0");
#endif // DEBUG

            NSURLCredential *newCredential;

            newCredential = [NSURLCredential credentialWithUser:USERNAME
                            password:PASSWORD
                            persistence:NSURLCredentialPersistenceForSession];

            [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge];

        }
        else
        {
            [[challenge sender] cancelAuthenticationChallenge:challenge];

            // inform the user that the user name and password
            // in the preferences are incorrect

#if 1 && defined(DEBUG)
            NSLog (@"didReceiveChallenge: Failed Authentication");
#endif // DEBUG

            // ...error will be handled by connection didFailWithError
        }
    }
#ifdef DEBUG
    else
    {
        NSLog(@"didReceiveChallenge: Not handled!");
    }

#endif // DEBUG
}

是否有类似＆＃34; lex的引理。 a ^ x = b＆＃34;在伊莎贝尔证明了吗？

1 个答案: