## 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

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

1.1 Overview peewee is a lightweight ORM written in python. ## Examples: Examples: # a simple query selecting a user User.get(User.username == 'charles') # get the staff and super users editors the where clause stuff gets crazy as there are args being combined with bitwise operators (“Q” expressions) and also kwargs being used with Django-style “double-understandscore” lookups. The crazy thing simple twitter-like site • using “fn” • the querying docs, which contain an in-depth overview of the query apis #### 1.3.3 Changes in fields and columns Well, for one, columns are gone. They were a shim

CONTENTS: ### 1.1 Overview peewee is a lightweight ORM written in python. Examples: # a simple query selecting a user User.get(username='charles') # get the staff and super users editors = User the exception can be caught during the “connect” step, rather than some arbitrary time later when a query is executed. >>> database = SqliteDatabase('stats.db') >>> database.connect() records, issue an UPDATE query. The following example will update all Entry objects, marking them as “published”, if their pub_date is less than today’s date. >>> update_query = Entry.update(published=True)

(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

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 1.8 Query operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 1.12 Query Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 1.13 Query Builder . . . . . . . . . . . . . . . . Twitter app written using Flask framework. • Guide to the various query operators describes how to construct queries and combine expressions. • Field types table lists the various field types peewee supports

/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

Contributing 17 1.6 Managing your Database 17 1.7 Models and Fields 35 1.8 Querying 50 1.9 Query operators 64 1.10 Foreign Keys 68 1.11 Performance Techniques 74 1.12 Transactions 78 1.13 between 5 and 10 minutes to go through it. • Guide to the various query operators describes how to construct queries and combine expressions. • Field types table lists the various field types peevee supports with your database connection immediately, as opposed to some arbitrary time later when the first query is executed. It is also good to close the connection when you are done – for instance, a web app might