Tecla SAP Dicas de inglês

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A: Back from the dentist already?
B: Yes, I hadn’t to didn’t have to wait long.
A: What did she say? Are your teeth OK?
B: Well, she must had to put a new filling in this tooth here.
A: Oh. But the other teeth are OK?
B: Yes, I mustn’t needn’t / don’t have to go back again till next year.

“ter de”, “dever”, “precisar”, “ser necessário”: must, have to

• must não tem nenhuma forma no passado, nem no present perfect, nem no future. O verbo substitutivo é have to.
  • Simple present: I must / have to call Bill. [Eu tenho de ligar para o Bill.]
  • Simple past: We had to (must) phone the doctor. [Era necessário ligar para o médico.]
  • Present perfect: I have / haven’t had to do this often. [Eu (não) precisei fazer isso muitas vezes.]
  • Future: You will / won’t have to wait. [Você (não) terá que esperar.]

mustn’t – needn’t – don’t have to

• “não precisar” é expresso por needn’t ou por don’t/doesn’t have to
  • I needn’t go / don’t have to (mustn’t) go yet. [Eu ainda não tenho de/não preciso ir agora.]
  • You needn’t worry. [Você não precisa se preocupar.]
  • I don’t have to work on Thursday. It’s a holiday. [Eu não preciso trabalhar...]

• must not corresponde a “não dever” e só pode ser usado no simple present:
  • I mustn’t forget. It’s Ann birthday tomorrow. [Não posso esquecer...]

Perguntas e negação com have to

• As negações e perguntas com have to formam presente e passado com alguma das formas de do.
  • I don’t have to go yet. – Does Ann have to go? – Yes, she does. / No, she doesn’t.
  • We didn’t have to wait long. – Did you have to call the police? – Yes, we did. / No, we didn’t.

Usamos must ou have to no presente?

• O uso de must e have to sobrepõe-se no presente. Erros podem ser evitados da seguinte maneira:
  • Ordem: must
    • Parent: You must be home by 9:30.
    • All bags must be left at the reception.
  • Para expressar os próprios sentimentos (a convicção pessoal): must
    • We must meet more often.
    • I must give up smoking.
  • Para relatar o que está sendo / foi ordenado por outros: have to
    • Child: My dad is awful. I have to be home by 9:30.
    • We have to pay at the machine before we fetch the car.
  • Perguntas: have to
    • Do we have to pay now?
    • Where do we have to park?

Cf. Gramática: Modal Verbs (1): CAN
Cf. Gramática: Modal Verbs (3): CAN, MAY, MIGHT, COULD

RESUMO

• must: usa-se apenas no simple present; nos outros tempos, usa-se have to.
• needn’t = “não precisar”: mustn’t = “não dever”
• have to: pergunta e negação com do
• must = “eu determino isso” ou “eu acho isso necessário”; have to = “outrem determina isso”

* Quanto ao uso americano > página 103 do livro

Referência: “Grammar – No problem” – Christine House e John Stevens, Disal Editora, 2005. Leia a resenha.