Aggregation So far, all SQL expressions have referred to values in a single row. Aggregation allows us to aggregate multiple rows together. Aggregation can be used in everywhere, bu...

SELECT statements A SELECT statement specifies an input table using FROM [table] SELECT [columns] FROM [table] WHERE [condition] ORDER BY [order]; SELECT [expression] AS [name],...

Databases Database management systems (DBMS) contains tables with records, which are rows that have a value for each column. Every table has columns and rows A column has a name...

Quasiquotation We may extend Lisp as a language itself. We may change the language however we want. We may extend Scheme by adding more procedures to it, such as a for loop func...

Programs as Data Scheme programs consist of expressions that can either be primitive* or **combinations. The built-in Scheme list data structure (a linked list) is used to represent combinatio...

Programs as data A scheme expression is just a scheme list. Thus, we may use scheme to write scheme programs ourselves Built-in Scheme list data strucutre may represent combinations Ex: sc...

Interpreters The scheme interpreter represents expressions as Pairs. For the operands, we must evaluate each of the values individually. This is because we may have compound expressio...

Interpreting Scheme There are two parts to an interpreter Eval: The eval evaluates primitive and combined expressions. It calls apply to apply a procedure to certain arguments in expr...

List Processing Procedures Review Built-in Methods: -(append s t): Concatenates two or more lists together into a new list -(map f s): Call a procedures f on each element of a list and retur...

Exceptions Exceptions allow us to raise an error for unexpected behaviors We may raise exceptions with the raise statement in Python: raise <expression> Expression must evaluate t...