Module 23 Flash Cards

Front 1

Thunk

Back 1

When we use a zeroargument function to delay evaluation we call the function a thunk. You can even say, “thunk the argument” to mean “use (lambda () e) instead of e”.

Front 2

Call-by-need

Back 2

If an argument is never used it is never evaluated, else it is evaluated only once.

Front 3

Call-by-value

Back 3

Arguments are fully evaluated before the call is made

Front 4

Stream

Back 4

A stream is an infinite sequence of values.

Front 5

Memoization

Back 5

An idiom related to lazy evaluation that does not actually use thunks is memoization.To implement memoization we do use mutation

Front 6

Macro definition

Back 6

A macro definition introduces some new syntax into the language. It describes how to transform the new syntax into different syntax in the language itself.

Front 7

Macro expansion

Back 7

The semantics of a macro use is to replace the macro use with the appropriate syntax as defined by the macro definition. This process is often called macro expansion because it is common but not required that the syntactic transformation produces a larger amount of code.