Help translating line from poem

this is a line from poem #44 of the ogura hyakunin isshu.

逢ふことの
絶えてしなくは

the part i am having trouble with is deciphering 絶えてしなくは.

what i have so far is:
絶える - to stop, to cease
て - 連用形 of つ
し - 連体形 of き
く - a nominalizer, like koto in modern japanese

i am having trouble figuring out what the な is. i originally thought that it was the 未然形 of ぬ, but that wouldn't work since ぬ attaches to the 連用形 but し is the 連体形.

can someone help me figure this out?

can someone help me figure this out?

I'm no good at classical grammar, but according to a book I have on the 百人一首:

二句「絶えてしなくは」の文法的な構造は、「絶えて（副詞）」＋「し（強調の助詞）」＋「なく（形容詞）」＋「は（助詞）」。「絶えて」は動詞がもとになっているが、あとに否定の語「なく」があるので、副詞としてとられてよい。「絶えて」と「なく」がセットで、「まったく...ない」と訳す。

(couple lines skipped)

二句の最後「は」は、たった一文字の中に仮定の意味をこめる。

(The book is 人に話したくなる百人一首 by あんの秀子)

Here is a site on the 百人一首 which gives a brief explanation of the grammar in the full poem. Since the 百人一首 is such a popular subject, there's lots of things around aimed at explaining things to beginners/people who have forgotten most of their high school lessons.

wow this site is a great resource! I have been looking for sites that give both translations of the poems and explanations of the grammar, but haven't been able to find any.

thanks for the link!

絶えて is originally derived from 絶ゆ, not 絶える, in classical grammar.
The site nekojita-san linked is not mentioned, but it's said that there are two different interpretations for this verse, 1) if I never had relations with her, and 2) if men and women never had relations.

You can see quite the same phrases in well-known poems/sayings such like;
世の中に絶えて桜のなかりせば春の心はのどけからまし
生きとし生けるすべてのもの