"to think about" in the beginning of a sentence [duplicate]

As a native speaker of English, the gerund version of this sentence sounds better:

infinitive:

When used together in chains, extension methods are an unprecedented tool to produce extremely concise code.

gerund:

When used together in chains, extension methods are an unprecedented tool for producing extremely concise code.

But how can I explain to someone learning English how to decide in situations like these whether to use the infinitive or the gerund?

From EnglishPage.com's article Gerunds and Infinitives Part 1, if you consider "to produce/for producing" as a complement in your phrase:

Both gerunds and infinitives can be used as the subject or the complement of a sentence.

However, as subjects or complements, gerunds usually sound more like normal, spoken English, whereas infinitives sound more abstract.
In the following sentences, gerunds sound more natural and would be more common in everyday English.
Infinitives emphasize the possibility or potential for something and sound more philosophical.

If this sounds confusing, just remember that 90% of the time, you will use a gerund as the subject or complement of a sentence.

Examples:

• Learning is important. normal subject
• To learn is important. abstract subject - less common
• The most important thing is learning. normal complement
• The most important thing is to learn. abstract complement - less common

I would like to share some of my thoughts.

Though the 90% rule is good enough for beginner and intermediate learners, I would like to add that, very likely, it would be insufficient for more advanced learners. (I'm not a native English speaker, so I understand the problem from their side perfectly.)

If your students are willing to remember grammar rules, then you are lucky, especially if your students are not those who their first languages have virtually no tense. If I understand it correctly, most Asian languages have no such thing. The tense is implied, not used explicitly as in English, which is why many Asian people find it so difficult to learn English. (Not to mention many other problems such as articles, phrasal verbs, propositions, and so on.)

One good cure is use the language (in this case, English) a lot. Much enough that the learners can reach some level of sense of the second language (L2). Unfortunately, this is easier said than done.

The next best thing, in my opinion, is to give some simple examples as the exemplars that they can rely on. So they can compare these example patterns to the grammatical problem they face.

Good exemplars should be simple enough, and yet still contradict the sense of first languages (L1) enough, to the point that they can realize the difference between the L1 and L2. A good exemplar for the use of gerund vs. infinitive that you mentioned, according to my own experience (myself and those who are close to me enough that I can help them), is:

I stop thinking.

I stop to think.

If they understand the profound difference between the two, they will develop the sense that helps them understand that which one is preferred, in which context. With such "language sense", they will be in much better position to deal with even difficult cases. They might not do it right the first time every time, but they will find the problem very easy to understand once being corrected.

Hope this is helpful.