differnce between -ant and -er/-ir/-re

Question

Hi,
since using the -ant and the infinitive both mean -ing in english, what's the difference between them and when would you use one and not the other?

Accepted Answer

Hi Nim,
Just to add to what Chris has just said, many verbs expressing likes and dislikes, (i.e. to love, to like, to prefer, to hate etc ), will be followed by a verb ending in  'ing' in English. 
In French, however,  as you have two verbs following each other ( two separate actions) the second verb will be in the infinitive. e.g.
I hate peeling potatoes = Je déteste éplucher les pommes de terre
I prefer walking to running= Je préfère marcher à courir
I enjoy cycling = J'aime faire du vélo
The 'ant' of the gerund (gérondif in French) conveys two concurrent actions, e.g.
Il travaille en sifflant (He wistles while working/he works)
Il marche en boitant (He walks with a limp)
Je l'ai aperçu en arrivant (I noticed him on arrival /when I arrived) 
Hope this helps!

Answer

Hi Nim,
the many uses of the English continuous form (-ing form) can lead to confusion when translating to/from French.
In the lesson you refer to, the continuous form really stands in for the infinitive. A good hint is that the infinitive even works in English, even though it isn't quite as natural as the -ing form:
Dieting is useful. -- To diet is useful. -- Faire un régime ist util.
I guess with the "-ant" form you mean the gerund. It serves a different purpose and cannot replace the inifinitive in the above examples.
En faisant un régime j'ai faim souvent. -- While dieting I am often hungry.Here the gerund expresses a simultaneity. Note that in English you could also omit "while" and still have the sentence work.
En prenant le train il a réussi à y arriver à l'heure. -- By taking the train he succeeded in arriving there in time. The gerund can also express causality, as in this example. Again, dropping "by" would also work in English.
The upshot is that the English infinitive is indistinguishable from the English gerund which is why a lot of English speaker don't know how to differentiate between them. In French they are distincly different concepts and not to be mixed.
-- Chris (not a native speaker).

Answer

...sorry, in my last paragraph I referred to the "English infinitive" but I really meant the English continuous form.
-- Chris.