Funzione da un insieme ad un altro.
Computable function, funzione calcolabile.
es: f(x) = 2x2 + 3x - 2
equation left side: name of the function and its formal parameter
right side: the defining expression.
This method of definition makes it impossible to specify the name f of the function independently of the name x of the formal parameter.
To separate them, Church adopted the greek letter λ as a marker of the defining
lambda expression
f = λx(2x2 + 3x - 2)
formal parameter ≡ bound variable the symbol x that appears after λ
body (of the expression) the remainder part
In this equation, the name f of the function appears by itself on the left, and its definition is a separate expression on the right.
In computer science, the clear separation of the name of a function from its defining expression enables a lambda expression to be used anywhere that a function name could be used. This feature is especially useful for applications that create new functions dynamically and pass them as arguments to other functions that evaluate them.
ref: jfsowa/math