[A] too + adjetivo/adverbio + infinitivo
1 too + adjetivo + infinitivo
- El infinitivo puede hacer referencia al sujeto de la oración. Tiene entonces significado activo:
- You are too young to understand. (You are so young that you cannot understand.)
- He was too drunk to drive home. (He was so drunk that he couldn’t drive home.)
(b) El infinitivo puede hacer referencia al objeto de un verbo. Tiene entonces significado pasivo:
- The plate was so hot that we couldn’t touch it
podría expresarse:
- The plate was too hot to touch. (too hot to be touched)
«it,» el objeto de «touch» en la primera oración, desaparece en la construcción de infinitivo, porque el infinitivo, aunque activo en la forma, es pasivo en significado.
A veces puede usarse indistintamente un infinitivo activo o un infinitivo pasivo:
- This parcel is too heavy to send/to be sent by post.
Pero esto no es siempre posible, así que a los estudiantes se les aconseja adherirse al infinitivo activo.
Puede colocarse for + nombre/pronombre delante del infinitivo en esta construcción:
- The case was too heavy (for a child) to carry =
= The case was too heavy to be carried by a child.
(c) El infinitivo puede hacer referencia al objeto de una preposición:
– The grass was so wet that we couldn’t sit on it.
The grass was too wet (for us) to sit on.
– The light is so weak that we can’t read by it.
The light is too weak to read by.
2 too + adjetivo + a + nombre + infinitivo
- He was too shrewd a businessman to accept the first offer =
= As a businessman he was too shrewd to accept the first offer.
- He is too experienced a conductor to mind what the critics say =
= As a conductor he is too experienced to mind what the critics say.
El infinitivo aquí siempre hace referencia al sujeto de la oración como en 1 arriba. Un infinitivo pasivo también es posible:
- He was too experienced a conductor to be worried by what the critics said.
3 too + adverbio + infinitivo
- It is too soon (for me) to say whether the scheme will succeed or not.
- He spoke too quickly for me to understand. («for me» es aquí necesario.)
- She works too slowly to be much use to me.
[B] Adjetivo/adverbio + enough + infinitivo
1 Adjetivo + enough + infinitivo
(a) Como en la construcción con too, el infinitivo puede hacer referencia al sujeto del verbo:
- She is old enough to travel by herself.
- He was tall enough to see over the heads of the other people.
(b) O puede hacer referencia al objeto del verbo:
- The case is light enough for me to carry =
= The case is so light that I can carry it.
- After a few minutes the coffee was cool enough (for us) to drink.
(c) Y también puede referirse al objeto de una preposición:
- The ice was thick enough to walk on.
- The light was strong enough to read by.
2 enough puede usarse como pronombre o como adjetivo:
- He doesn’t earn enough (money) to live on.
- We haven’t enough time to do it properly.
- She had enough sense to turn off the gas.
have + enough + nombre abstracto es a veces reemplazable por have + the + nombre:
- She had the sense to turn off the gas.
- He had the courage to admit his mistake.
- I hadn’t the patience to listen any more.
the es opcional delante de time: We haven’t (the) time to do it properly.
3 Adverbio + enough + infinitivo:
- He didn’t jump high enough to win a prize.
- He spoke slowly enough for everyone to understand
[C] so + adjetivo + as + infinitivo:
- He was so foolish as to leave his car unlocked.
Es una alternativa a la construcción con enough en B1 arriba, pero notar que «He was foolish enough to leave his car unlocked» puede significar tanto que así lo hizo como que era capaz de hacerlo, pero «He was so foolish as to leave etc.» implica que efectivamente lo hizo.
La construcción so … as no se usa muy a menudo como se mostró arriba, pero es muy corriente como forma de petición:
- Would you be so good as to forward my letters? =
= Would you be good enough to forward my letters?
No hay diferencia de significado entre las dos formas. Es importante no olvidar el as.
A Practical English Grammar (A.J. Thomson & A.V. Martinet) 