Finally, de+ infinitive can have the effect of a conditional clause introduced
by si:De saberlo no habría pagado.If I had known I wouldn’t have
paid.Al+ infinitive
The sequence al + infinitive occurs with an equivalent sense to English ‘on’
+ ‘-ing’ or to mean ‘when’:Al ver lo que había pasado se puso a llorar.
On seeing/When he saw what had happened he started crying.Infinitives in impersonal constructions
Infinitives often occur in impersonal constructions, i.e. constructions in
which no individual person or thing is the subject of the main verb. Possibly
the most common construction of this sort is formed from haber + que +
infinitive, for which see 16.3.An infinitive may also be used after ser when followed by an obligation word
like preciso‘necessary’, obligatorio‘compulsory’, necesario‘necessary’:
Fue preciso llamar a un It was necessary to call a doctor.
médico.Es obligatorio reservar una It is compulsory to reserve a
plaza. place.
An infinitive can also be used after the formulas se ruegaand se prohíbe:
Se ruega no tocar las Customers are asked not to
mercancías. touch the merchandise.Se prohíbe fumar. Smoking is forbidden.An infinitive as the subject of a verb
An infinitive (together with its object, if any) can function as the subject of
a finite verb, although it may be placed after it:Cenar con ellos fue una Having dinner with them was a
pesadilla. nightmare.17.4
17.3
17.2.5.31111
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1011
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20111
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30111
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17
Infinitive
constructions