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      floating point literal

      De cppreference.com

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      <metanoindex/>

       
      C++
       
      Linguagem C++
      Tópicos gerais
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      General topics
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      Controle de fluxo
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      Flow control
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      Declarações execução condicional
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      Conditional execution statements
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      Instruções de iteração
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      Iteration statements
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      Ir declarações
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      Jump statements
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      Funções
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      Functions
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      declaração da função
      lambda declaração da função
      modelo de função
      linha especificador
      especificações de exceção (obsoleta)
      noexcept especificador (C++11)
      Exceções
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      Exceptions
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      Namespaces
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      Namespaces
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      Tipos
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      Types
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      decltype specifier (C++11)
      Especificadores
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      Specifiers
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      cv especificadores
      armazenamento duração especificadores
      constexpr especificador (C++11)
      auto especificador (C++11)
      alignas especificador (C++11)
      Inicialização
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      Initialization
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      Literais
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      Literals
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      Expressões
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      Expressions
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      representações alternativas
      Utilitários
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      Utilities
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      Tipos
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      Types
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      typedef declaration
      tipo de alias declaração (C++11)
      atributos (C++11)
      Conversões
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      Casts
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      conversões implícitas
      const_cast conversion
      static_cast conversion
      dynamic_cast conversion
      reinterpret_cast conversion
      Elenco C-estilo e funcional
      Alocação de memória
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      Memory allocation
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      Classes
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      Classes
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      Classe propriedades específicas de função
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      Class-specific function properties
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      Funções membro especiais
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      Special member functions
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      Modelos
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      Templates
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      modelo de classe
      modelo de função
      especialização de modelo
      pacotes de parâmetros (C++11)
      Diversos
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      Miscellaneous
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      Assembly embutido
       
      Ponto flutuante literal define uma constante em tempo de compilação, cujo valor é especificado no arquivo de origem.
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      Floating point literal defines a compile-time constant whose value is specified in the source file.
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      Sintaxe

      A literais de ponto flutuante tem duas sintaxes. A primeira é constituída pelas seguintes partes:
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      A floating-point literals have two syntaxes. The first one consists of the following parts:
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      • seqüência de dígitos decimais não vazio contendo um caractere de ponto decimal (define significativo)
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        nonempty sequence of decimal digits containing a decimal point character (defines significant)
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      • (opcional) e ou E seguiu com menos opcionais ou sinal de mais e não vazio seqüência de dígitos decimais (define expoente)
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        (opcional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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      • (opcional) um especificador de tipo sufixo como l, f, L ou F
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        (opcional) a suffix type specifier as a l, f, L or F
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      O segundo consiste nas seguintes partes:
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      The second one consists of the following parts:
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      • seqüência não vazia de dígitos decimais (define significativo)
        Original:
        nonempty sequence of decimal digits (defines significant)
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      • e ou E seguiu com menos opcionais ou sinal de mais e não vazio seqüência de dígitos decimais (define expoente)
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        e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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      • (opcional) um especificador de tipo sufixo como l, f, L ou F
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        (opcional) a suffix type specifier as a l, f, L or F
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      O sufixo especificador de tipo define o tipo real do literal de ponto flutuante:
      Original:
      The suffix type specifier defines the actual type of the floating-point literal:
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      • (Sem sufixo) define double
        Original:
        (no suffix) defines double
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      • f F define float
        Original:
        f F defines float
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      • l L define long double
        Original:
        l L defines long double
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      Explicação

      Uma notação decimal científico é usado, o que significa que o expoente é a potência de 10, através da qual o importante é multiplied.
      Original:
      A decimal scientific notation is used, meaning that the exponent is the power of 10 by which the significant is multiplied.
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      O significado matemático de 123e4 é 123 × 10 4 </ sup>
      Original:
      The mathematical meaning of 123e4 is 123×104
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      Exemplo

      std::cout << 123.456e-67 << '\n'
          << .1E4f       << '\n'
          << 58.         << '\n'
          << 4e2         << '\n';

      Saída: 

      1.23456e-65
1000
58
400