Learn Farsi: نمی‌شود در کتابخانه تند راه رفت.

In Farsi, to say 'one can' or 'one cannot' do something as a general rule, we use می‌شود or نمی‌شود followed by the short infinitive. The short infinitive is simply the past stem of the verb, formed by dropping the final ن from the full infinitive. So, راه رفتن becomes راه رفت.

رفت looks like the past tense for 'he/she went'. Does this sentence talk about the past?

Not at all! While رفت is indeed the past stem and looks identical to the simple past tense for 'he/she went', in this specific structure (نمی‌شود + short infinitive), it carries no past tense meaning. It simply acts as a base form to express a general, timeless rule.

راه رفت is a compound verb. How does the short infinitive rule apply to it?

The rule only changes the actual verb portion of the compound. The non-verb part (راه, meaning 'way' or 'path') stays exactly the same. The verb part (رفتن) drops its final ن to become رفت. Together, they form the compound short infinitive راه رفت.

Could I place تند (fast) at the very end of the sentence, like in English?

Usually, no. In Farsi, adverbs of manner like تند strongly prefer to go directly before the verb they describe. Because راه رفت functions together as the compound verb here, تند is placed right before the entire compound block.