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  2. Real-valued function - Wikipedia

    en.wikipedia.org/wiki/Real-valued_function

    In mathematics, a real-valued function is a function whose values are real numbers. In other words, it is a function that assigns a real number to each member of its domain . Real-valued functions of a real variable (commonly called real functions ) and real-valued functions of several real variables are the main object of study of calculus and ...

  3. Bellman equation - Wikipedia

    en.wikipedia.org/wiki/Bellman_equation

    The Bellman equation is classified as a functional equation, because solving it means finding the unknown function , which is the value function. Recall that the value function describes the best possible value of the objective, as a function of the state . By calculating the value function, we will also find the function () that describes the ...

  4. Python (programming language) - Wikipedia

    en.wikipedia.org/wiki/Python_(programming_language)

    The syntax :=, called the "walrus operator", was introduced in Python 3.8. It assigns values to variables as part of a larger expression. [106] In Python, == compares by value. Python's is operator may be used to compare object identities (comparison by reference), and comparisons may be chained—for example, a <= b <= c.

  5. Function of a real variable - Wikipedia

    en.wikipedia.org/wiki/Function_of_a_real_variable

    A real-valued function of a real variable is a function that takes as input a real number, commonly represented by the variable x, for producing another real number, the value of the function, commonly denoted f(x). For simplicity, in this article a real-valued function of a real variable will be simply called a function. To avoid any ambiguity ...

  6. Sign function - Wikipedia

    en.wikipedia.org/wiki/Sign_function

    The signum function of a real number is a piecewise function which is defined as follows: [1] ⁡:= {<, =, > The law of trichotomy states that every real number must be positive, negative or zero. The signum function denotes which unique category a number falls into by mapping it to one of the values −1 , +1 or 0, which can then be used in ...

  7. Function (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Function_(mathematics)

    In calculus, a real-valued function of a real variable or real function is a partial function from the set of the real numbers to itself. Given a real function f : x ↦ f ( x ) {\displaystyle f:x\mapsto f(x)} its multiplicative inverse x ↦ 1 / f ( x ) {\displaystyle x\mapsto 1/f(x)} is also a real function.

  8. Characteristic function (probability theory) - Wikipedia

    en.wikipedia.org/wiki/Characteristic_function...

    This function is real-valued because it corresponds to a random variable that is symmetric around the origin; however characteristic functions may generally be complex-valued. In probability theory and statistics, the characteristic function of any real-valued random variable completely defines its probability distribution.

  9. Python syntax and semantics - Wikipedia

    en.wikipedia.org/wiki/Python_syntax_and_semantics

    In all versions of Python, boolean operators treat zero values or empty values such as "", 0, None, 0.0, [], and {} as false, while in general treating non-empty, non-zero values as true. The boolean values True and False were added to the language in Python 2.2.1 as constants (subclassed from 1 and 0 ) and were changed to be full blown ...