Back to Basics Lambda Expressions Barbara Geller & Ansel Sermersheim CppCon September 2020Introduction ● Prologue ● History ● Function Pointer ● Function Object ● Definition of a Lambda Expression slot library ○ CsLibGuarded ■ library for managing access to data shared between threadsLambda Expressions ● History ○ lambda calculus is a branch of mathematics ■ introduced in the 1930’s to prove memory ■ languages which were influenced by lambda calculus ● Haskell, LISP, and ML 5Lambda Expressions ● History ○ why do we use the terminology lambda expression ■ greek letter λ refers to an anonymous

About me 2 6 ways for implementing math expressions calculator, Amir Kirsh Lecturer Academic College of Tel-Aviv-Yaffo and Tel-Aviv University Developer Advocate at Member of the Israeli ISO C++ NB NB Co-Organizer of the CoreCpp conference and meetup group3 6 ways for implementing math expressions calculator, Amir Kirsh Suffering from slow builds? It’s not just waste of time It affects your dev implementing math expressions calculator, Amir KirshSuccess Stories 5 6 ways for implementing math expressions calculator, Amir KirshSuccess Stories 6 6 ways for implementing math expressions calculator, Amir

expression doesn’t introduce an extra level of optionality to expressions that already return optionals. Large integer literal initialization expressions are inferred to be of the correct integer type. For example teamScore += 1 8 } 9 } 10 print(teamScore) 11 // Prints "11" In an if statement, the conditional must be a Boolean expression— this means that code such as if score { ... } is an error, not an clause that sets a different greeting if optionalName is nil. If the optional value is nil, the conditional is false and the code in braces is skipped. Otherwise, the optional value is unwrapped and assigned

. . . . . . . . . . . . 19 1.2.12 $ELSE : Switch conditional compilation . . . . . . . . . . . . . . . . . . . 19 1.2.13 $ELSEC : Switch conditional compilation . . . . . . . . . . . . . . . . . . . $ELIFC : Switch conditional compilation . . . . . . . . . . . 20 1.2.15 $ENDC : End conditional compilation . . . . . . . . . . . . . . . . . . . . . 20 1.2.16 $ENDIF : End conditional compilation . . . . . . . . . . . . . 23 1.2.29 $IF : Start conditional compilation . . . . . . . . . . . . . . . . . . . . . . 23 1.2.30 $IFC : Start conditional compilation . . . . . . . . . . . . . . . . . .

the configuration file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 5.2.1 Conditional processing of the config file . . . . . . . . . . . . . . . . . . . . 36 5.2.2 #CFGDIR . . . opened. • p : Write parse tree (tree.log) • q : Show message numbers. • c : Notify on each conditional being processed. • mxxx : xxx is a comma-separated list of messages numbers which should not be Generate profiler code for gprof. This will define the symbol FPC_PROFILE, which can be used in conditional defines. 30 CHAPTER 5. COMPILER CONFIGURATION -PB Show default Target CPU compiler binary -PP

6 } else { 7 teamScore += 1 8 } 9 } 10 teamScore In an if statement, the conditional must be a Boolean expression—this means that code such as if score { ... } is an error, not an clause that sets a different greeting if optionalName is nil. If the optional value is nil, the conditional is false and the code in braces is skipped. Otherwise, the optional value is unwrapped and assigned appropriate-sized number type (such as UInt8 in the example above) and can therefore be used in expressions alongside other values of the same type. ​ Int In most cases, you don’t need to pick a specific

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3 Expressions 15 3.1 Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.9 Unit Expressions and Parenthesized Expressions . . . . . . . . . . . . . . . . . . . . . . . . 21 3.10 Arithmetic Sequences . . . . . . . . . . . . . . 21 3.12 Let Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.13 Case Expressions . . . . . . . . . . . . . . . . . . . .

MIDDLEWARE Conditional View Processing The condition decorator Shortcuts for only computing one value Using the decorators with other HTTP methods Comparison with middleware conditional processing options Model instance reference QuerySet API reference Lookup API reference Query Expressions Conditional Expressions Database Functions Paginator Paginator class Page class Exceptions Request and response Indexes | Meta options | Model class QuerySets: Making queries | QuerySet method reference | Lookup expressions Model instances: Instance methods | Accessing related objects Migrations: Introduction to Migrations

MIDDLEWARE Conditional View Processing The condition decorator Shortcuts for only computing one value Using the decorators with other HTTP methods Comparison with middleware conditional processing options Model instance reference QuerySet API reference Lookup API reference Query Expressions Conditional Expressions Database Functions Request and response objects Quick overview HttpRequest objects Indexes | Meta options | Model class QuerySets: Making queries | QuerySet method reference | Lookup expressions Model instances: Instance methods | Accessing related objects Migrations: Introduction to Migrations

MIDDLEWARE Conditional View Processing The condition decorator Shortcuts for only computing one value Using the decorators with other HTTP methods Comparison with middleware conditional processing options Model instance reference QuerySet API reference Lookup API reference Query Expressions Conditional Expressions Database Functions Request and response objects Quick overview HttpRequest objects Indexes | Meta options | Model class QuerySets: Making queries | QuerySet method reference | Lookup expressions Model instances: Instance methods | Accessing related objects Migrations: Introduction to Migrations