## Back to Basics Lambda Expressions Barbara Geller & Ansel Sermersheim CppCon September 2020 ## I ntroduction • Prologue • History • Function Pointer • Function Object • Definition of a Lambda library ☐ CsLibGuarded ☑ library for managing access to data shared between threads ## Lambda Expressions ## • History ○ $ \lambda $ calculus is a branch of mathematics ■ introduced in the 1930’s memory ■ languages which were influenced by lambda calculus • Haskell, LISP, and ML ## Lambda Expressions ## • History ☐ why do we use the terminology lambda expression ☑ greek letter $ \lambda $

## +23 ## Six Ways for Implementing Math Expressions Calculator ## AMIR KIRSH 20 23 October 01 - 06 ## About me ## Lecturer Academic College of Tel-Aviv-Yaffo and Tel-Aviv University ## Developer [Image](/uploads/documents/4/5/b/8/45b8c80c4fc816ade243ff11567a25e4/p9_2.jpg) # Six ways for Implementing Math Expressions Calculator A walk through polymorphism, smart pointers, templates, concepts and more Amir Kirsh necessarily...) Shorter (and nicer?) code. No need for allocations! And... we may even evaluate expressions at compile time! ## Let's see the code http://coliru.stacked-crooked.com/a/5060e5f189135362

(Luke Valenty) Assigned to: elbeno (Ben Deane) Factor arbitrary matcher expressions into "sum-of-products" expressions ## Part 1 Fields and messages: how they are structured and specified. ## ## Boolean algebra primer/refresher In upcoming slides you'll see some Boolean expressions (not necessarily in C++). Just so we're all clear, I'm using this convention: • ^ means simple as possible. ## Example matcher problems We've made it easy for people to write complex expressions, possibly containing tautologies or contradictions, or at least common parts... How does the library

/9/6/a396eece687d6cc18563188e015082da/p2_1.jpg) Andreas Fertig B2B: C++ Templates ## Fold Expressions  ■ Used to unpack Print("Hello", "C++", 20); 15 } ## Fold Expressions 10 Normalize functions for 'normal' strings 2 auto Normalize(const std::string& t) /9/6/a396eece687d6cc18563188e015082da/p3_1.jpg) Andreas Fertig B2B: C++ Templates ## Fold Expressions 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

closely matches lvalue references • it may refer to const objects • it does not bind to rvalue expressions • declaring reference_wrapper does not odr-use T ## Deduce from const-qualified lvalues

Model instance reference ■ QuerySet API reference ■ Lookup API reference ■ Query Expressions ■ Conditional Expressions ■ Database Functions ## • Request and response objects Quick overview ■ HttpRequest Meta options | Model class • QuerySets: Executing queries | QuerySet method reference | Lookup expressions • Model instances: Instance methods | Accessing related objects • Migrations: Introduction to Transactions | Aggregation | Custom fields | Multiple databases | Custom lookups | Query Expressions | Conditional Expressions | Database Functions • Other: Supported databases | Legacy databases | Providing

statements ..... 151 7.3 Code blocks ..... 152 7.3.1 Coercion to kotlin.Unit ..... 153 8 Expressions ..... 155 Glossary ..... 155 Introduction ..... 155 8.1 Constant literals ..... 155 8.1 159 8.2 Constant expressions ..... 159 8.3 String interpolation expressions ..... 159 8.4 Try-expressions ..... 161 8.5 Conditional expressions ..... 163 8.6 When expressions ..... 164 8.6.1 when expressions ..... 167 8.7 Logical disjunction expressions ..... 169 8.8 Logical conjunction expressions ..... 169 8.9 Equality expressions ..... 169 8.9.1 Reference equality expressions ...

Conclusion … 24 II. The SQL Language … 25 SQL Syntax … 33 4.1. Lexical Structure … 33 4.2. Value Expressions … 42 4.3. Calling Functions … 56 Data Definition … 59 5.1. Table Basics … 59 5.2. Default Values 115 6.4. Returning Data from Modified Rows … 115 Queries … 117 7.1. Overview … 117 7.2. Table Expressions … 117 7.3. Select Lists … 133 7.4. Combining Queries (UNI ON, I NTERSECT, EXCEPT) … 135 7.5. Sorting BY) … 136 7.6. LI M T and OFFSET … 137 7.7. VALUES Lists … 137 7.8. WITH Queries (Common Table Expressions) … 138 Data Types … 148 8.1. Numeric Types … 149 8.2. Monetary Types … 155 8.3. Character Types

Conclusion … 26 II. The SQL Language … 27 SQL Syntax … 35 4.1. Lexical Structure … 35 4.2. Value Expressions … 44 4.3. Calling Functions … 59 Data Definition … 62 5.1. Table Basics … 62 5.2. Default Values Table Expressions … 118 7.3. Select Lists … 134 7.4. Combining Queries … 136 7.5. Sorting Rows … 137 7.6. LI M T and OFFSET … 138 7.7. VALUES Lists … 139 7.8. WITH Queries (Common Table Expressions) … 140 Conditional Expressions … 346 9.19. Array Functions and Operators … 349 9.20. Range Functions and Operators … 352 9.21. Aggregate Functions … 355 9.22. Window Functions … 361 9.23. Subquery Expressions … 363

Special Characters ...35 4.1.5. Comments ...35 4.1.6. Operator Precedence ...36 4.2. Value Expressions ...37 4.2.1. Column References ...38 4.2.2. Positional Parameters ...38 4.2.3. Subscripts . 4.2.6. Function Calls ...40 4.2.7. Aggregate Expressions ...40 4.2.8. Window Function Calls ...43 4.2.9. Type Casts ...45 4.2.10. Collation Expressions ...45 4.2.11. Scalar Subqueries ...46 4.2.12 5.5.1. Adding a Column ...68 5.5.2. Removing a Column ...68 5.5.3. Adding a Constraint ...68 5.5.4. Removing a Constraint ...69 5.5.5. Changing a Column’s Default Value ...69 5.5.6. Changing a Column’s