Practically, pure functions do not: ○ contain state (static variables or class member variables) ○ mutate input parametersPure Functions ● A pure function is a function that ○ is deterministic: They always return Practically, pure functions do not: ○ contain state (static variables or class member variables) ○ mutate input parameters ● A function is pure if and only if it could be replaced by a lookup table (potentially of these functions are pure ● get_timestamp gets the time from the local machine ○ That is an input side effect(im)Pure Functions ● Here is a simple implementation of a smoothing filter ● None of

fk_output_fite，'w') as f,write(code) offsets， types}， trim_btock fast_fk::internat { data_size = 2 + *input_data，std::size t std::array< ，{ffrotationsltengthj}* 9> R_att = { rotation in rotations row in ernat( +input_data，std::size std::array< stdi:array< + 3> offset_att = fast_fk::internat { data size = 2 + 3+ 9 +2 num_of joints = {{rotations|tength}}; gtobal { +input_data，std::size = btockIdx.x * bockDim.x + threadIdx .xi (idx * data size * num of joints >= totat_ size) { 】 input_data += (idx * data_sizernum_of joints); R_atLIffrotations|tength}j* 9] {- for rotation in rotations

std::vector doubleNumbers(std::vector input) 02: { 03: std::vector output; 04: for(auto str: input) 05: { 06: int asInt = convertStringToInt(str); std::vector doubleNumbers(std::vector input) 02: { 03: std::vector output; 04: for(auto str: input) 05: { 06: int asInt = convertStringToInt(str); output; 11: } 1: std::vector doubleNumbers(std::vector input) 2: { 3: return input 4: .transform(convertStringToInt) 5: .transform(doubleInt) 6:

Functional Programming in C++ CppCon 2024-09-19 9Example: Biggest odd magnitude Problem statement Input Non-empty list of integers Output The biggest magnitude of an odd integer in the list Jonathan Müller 10Example: Biggest odd magnitude Problem statement Input Non-empty list of integers Output The biggest magnitude of an odd integer in the list Input [3, 0, 2, -1, 5, -7, 8] Output 7 Jonathan Müller Back to Basics: Functional Programming in C++ CppCon 2024-09-19 17Composition shape: Range → Range Input Range Output Range with different values or a different size Jonathan Müller — @foonathan Back to

rvalue getInputs() Also, because it is right associative. Right associativity allows rvalues as input17 inputs | transform(f) | filter(p) | push_back(results) ( ) object holding a reference to inputs pipes The output of a pipeline Simple container adapters Complex container adapters for_each31 INPUT: RANGES auto const inputs = std::vector{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; auto results = std::vector{}; pipes::push_back(results); 32 INPUT: RANGES range33 INPUT: STL ALGORITHMS std::set_difference34 INPUT: STL ALGORITHMS push_back std::set_difference results35 INPUT: STL ALGORITHMS push_back std::set_difference

template • No extensibility • No customization for different scenario for the same type LOG("Input is: {}", input); A better way is using a formatting-like interface, and a stateful functor: template Input is: {}", input); LOG("Input is: {}", input); Logging macro:Do I catch the bug? Yes, and it’s inside a unit test case parseExpr(std::string input) { static std::map cache; if (cache.count(input) == 0) { Expr* expr = parse_the_input(input) cache[input] = expr; return expr; } else { return cache[input]->Clone();

DatabaseMatrix Multiplication 56Matrix Multiplication Input A Input B x: 0, y: 0, len_x:2, len_y:2 Output C 57Input A Input B Output C Input A Input B Output C Matrix Multiplication 58 fern::Interval l fern::Interval (y, out.y_start, out.y_start + out.y_len, l fern::Compute( fern::Producer(Input A Input B Output C Matrix Multiplication 59 fern::Interval (x, C.R_start, C.R_start + C.R_len, len_x)( l fern::Interval (y, out.y_start, out.y_start + out.y_len, l fern::Compute( fern::Producer(Input A Input B Output C Matrix Multiplication 60 fern::Interval (x, C.R_start, C.R_start + C.R_len, len_x)(

const buf_len) { rf_512 prev; //- Bottom of the input data window rf_512 curr; //- Middle of the input data window rf_512 next; //- Top of the input data window rf_512 lo; //- Primary work register const buf_len) { rf_512 prev; //- Bottom of the input data window rf_512 curr; //- Middle of the input data window rf_512 next; //- Top of the input data window rf_512 lo; //- Primary work register const buf_len) { rf_512 prev; //- Bottom of the input data window rf_512 curr; //- Middle of the input data window rf_512 next; //- Top of the input data window rf_512 lo; //- Primary work register

General Utilities Containers Iterators Algorithms Strings Ranges Numerics Time Localization Input/Output Regular Expressions Atomic Operations Thread Support The C++20 Standard LibraryCppCon 2021 Original Utilities Containers Iterators Algorithms Strings Ranges Numerics Time Localization Input/Output Regular Expressions Atomic Operations Thread Support The C++20 Standard Library New General some business problem to solve • We begin with input data • We read that data and perform computations • We generate and write some desired output 7 Input Computation Output Read WriteCppCon 2021

gained? 16 . 1Copyright Jason Turner @le�icus emptycrate.com/idocpp Scripting Funnel parsed input any dispatch(string_view name, span params) string to_string(int) int add(int Imagine this was your input file: 1 print(to_string(1 - (3 * 6))) 16 . 4Copyright Jason Turner @le�icus emptycrate.com/idocpp Scripting Integration Imagine this was your input file: 1 print(to_string(1 4Copyright Jason Turner @le�icus emptycrate.com/idocpp Scripting Integration Imagine this was your input file: 1 print(to_string(1 - (3 * 6))) or 1 (print (to_string (- 1 (* 3 6)))) or (with effectively