5 exercises — choosing between infinitive purpose clauses, in order to, so as not to, and finite so that clauses in specs and RFCs.
Key patterns:
to + verb — standard infinitive of purpose
in order to — more formal, emphasizes deliberateness
so as not to / in order not to — negative purpose
so that + subject + modal — required when the purpose clause has a different subject
0 / 5 completed
1 / 5
Which sentence correctly uses a non-finite infinitive clause of purpose in a design doc?
The infinitive of purpose, "to + base verb", is the standard way to express why something was done: to handle transient failures. Option A uses "for + gerund", which expresses function (what a thing is generally used for) rather than the specific purpose behind this action, and reads oddly with an active decision like "we added". Option C mixes "for" and "to", which is ungrammatical. Option D uses a present participle, which suggests simultaneous description rather than purpose.
2 / 5
Choose the sentence that correctly uses "in order to" versus plain "to" for emphasis on deliberate purpose in an RFC:
"In order to" is followed directly by the bare infinitive (to prevent) and is used to emphasize deliberateness or add formality compared to plain "to". Option B omits "to" after "order". Option C incorrectly inserts "for" between "order" and the verb. Option D uses a gerund (preventing) instead of the required infinitive form after "to".
3 / 5
Which sentence correctly uses a negative purpose clause with "so as not to" or "in order not to" in a code comment?
In the negative purpose construction, "not" goes immediately before "to", giving so as not to overwrite. Option A incorrectly splits the infinitive by placing "not" after "to" instead of before it (a stylistic and conventional error in this fixed phrase). Option C misplaces "not" before "so as", changing the logical scope. Option D combines "to" with a gerund, which is ungrammatical after this construction.
4 / 5
A specification states: "The API returns a 429 status _____ signal that the client should back off." Which non-finite structure correctly completes this purpose clause?
"To signal" is the correct infinitive of purpose, explaining why the API returns that status code. "For signaling" (option A) suggests general function rather than specific intent and is less idiomatic in this deliberate-action context. "Signaling" alone (option C) would describe simultaneous action, not purpose, and would need to modify a different element of the sentence. "For signal" (option D) is ungrammatical — "for" requires a gerund, not a bare noun/verb, in this pattern.
5 / 5
Which sentence correctly uses a purpose clause with "so that" plus a modal verb, contrasted with a non-finite infinitive clause, for a scenario requiring a different subject in the purpose clause?
When the purpose clause has a different subject from the main clause (here, "operators" rather than the implied "we/you" who adds the flag), a finite so that + subject + modal clause is required, not a bare infinitive. Option B is correct. Option A's infinitive clause implicitly refers back to the main clause's subject, losing the specific "operators" actor. Option C attempts a "for + object + to-infinitive" pattern but incorrectly uses the gerund "disabling" instead of the bare infinitive "disable". Option D omits the necessary conjunction "so that", producing a run-on sentence.