![]() You can declare the types of function arguments by appending ::TypeName to the argument name, as usual for Type Declarations in Julia. This can be seen if we call f(x, y): julia> a = Īs a common convention in Julia (not a syntactic requirement), such a function would typically be named f!(x, y) rather than f(x, y), as a visual reminder at the call site that at least one of the arguments (often the first one) is being mutated. On the other hand, the assignment y = 7 + y changes the binding ("name") y to refer to a new value 7 + y, rather than mutating the original object referred to by y, and hence does not change the corresponding argument passed by the caller. The statement x = 42 mutates the object x, and hence this change will be visible in the array passed by the caller for this argument. Y = 7 + y # new binding for y, no mutation (This is the same behavior found in Scheme, most Lisps, Python, Ruby and Perl, among other dynamic languages.)įor example, in the function function f(x, y) Modifications to mutable values (such as Arrays) made within a function will be visible to the caller. Function arguments themselves act as new variable bindings (new "names" that can refer to values), much like assignments argument_name = argument_value, so that the objects they refer to are identical to the passed values. ![]() Julia function arguments follow a convention sometimes called "pass-by-sharing", which means that values are not copied when they are passed to functions. Without parentheses, the expression f refers to the function object, and can be passed around like any other value: julia> g = f Īs with variables, Unicode can also be used for function names: julia> ∑(x,y) = x + y The short function syntax is accordingly quite idiomatic, considerably reducing both typing and visual noise.Ī function is called using the traditional parenthesis syntax: julia> f(2,3) Short, simple function definitions are common in Julia. In the assignment form, the body of the function must be a single expression, although it can be a compound expression (see Compound Expressions). The traditional function declaration syntax demonstrated above is equivalent to the following compact "assignment form": julia> f(x,y) = x + y There is a second, more terse syntax for defining a function in Julia. This function accepts two arguments x and y and returns the value of the last expression evaluated, which is x + y. The basic syntax for defining functions in Julia is: julia> function f(x,y) Julia functions are not pure mathematical functions, because they can alter and be affected by the global state of the program. In Julia, a function is an object that maps a tuple of argument values to a return value.
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