First of all, this is not a duplicate... E.g., have a look at these posts:
"as ... as" or "so ... as" for comparison?
Anytime people on those posts talked about the use of 'so...as...', they said either that it can be used 'only in negative context' or that it can be used 'only with negative comparatives'.
Well, it is not clear to me at all what is meant by 'negative context/comparatives'... I am quite sure there was something significant omitted in the explanations. E.g., look at the following sentences:
Like the coordinating conjunctions, it is perfectly fine to begin sentences with because, so long as you keep in mind that the goal is to avoid fragments.
(Source: https://ell.stackexchange.com/a/564/6697).
This sentence does not seem to contain any 'negative context/comparatives'.
So foolish, unreasonable, or out of place as to be amusing.
(Source: the definition of 'ludicrous' on Oxford Dictionaries).
This sentence does not seem to contain any 'negative context/comparatives' either.
And this post was not meant to be derogative in any way... I am sorry if anyone got offended.
I have also left the exact URLs of most of the websites I have linked to (without having used the hyperlink function) so as to let the users see some information about the links given before having them clicked on the link.
(additionally, is 'before having them clicked on the link' grammatical? I am not a native English speaker and I'm trying to get a hang of some more advanced kind of structures).
Some justifications of the uses of 'so...as...' in the two given sentences would be appreciated (as well as some other grammar corrections present in this post, if possible). Thanks!