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In languages which support first-class functions and currying, map may be partially applied to lift a function that works on only one value to an element-wise equivalent that works on an entire container; for example, map square is a Haskell function which squares each element of a list.
Go has built-in, language-level support for associative arrays, called "maps". A map's key type may only be a boolean, numeric, string, array, struct, pointer, interface, or channel type. A map type is written: map[keytype]valuetype. Adding elements one at a time:
Another example in JavaScript uses the built-in methods of Array: filter somethings . filter ( x => x . count > 10 ) . sort (( a , b ) => a . count - b . count ) . map ( x => x . name ) Note that in JavaScript filter and map return a new shallow copy of the preceding array but sort operates in place.
In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms, an associative array is a function with finite domain. [1] It supports 'lookup', 'remove', and 'insert ...
In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine. For example, if x is an array, then y = sin (x) will result in an array y whose elements are sine of the corresponding elements of the array x. Vectorized index operations are also supported.
An internal iterator is a higher order function (often taking anonymous functions) that traverses a collection while applying a function to each element. For example, Python's map function applies a caller-defined function to each element:
Here, the list [0..] represents , x^2>3 represents the predicate, and 2*x represents the output expression.. List comprehensions give results in a defined order (unlike the members of sets); and list comprehensions may generate the members of a list in order, rather than produce the entirety of the list thus allowing, for example, the previous Haskell definition of the members of an infinite list.
The examples are not intended to compare and contrast programming languages, but to serve as examples of higher-order function syntax. In the following examples, the higher-order function twice takes a function, and applies the function to some value twice. If twice has to be applied several times for the same f it preferably should return a ...