Tag surrogate

A "tag surrogate" is a concept in computer science and programming that refers to a temporary or intermediate value that is used to hold the result of an operation or expression, rather than the original value itself.

In other words, a tag surrogate is a placeholder or a stand-in for the original value, which is used to facilitate the execution of a particular operation or algorithm. The tag surrogate is typically used to avoid modifying the original value or to provide a temporary value that can be used as an intermediate result.

Here are some examples of tag surrogates:

1. In functional programming, a tag surrogate is often used to create a new value that is derived from an original value, without modifying the original value.
2. In data processing, a tag surrogate can be used to hold the result of a calculation or transformation, before it is written to a final destination.
3. In computer graphics, a tag surrogate can be used to hold the result of a rendering operation, before it is displayed on the screen.

The term "tag surrogate" is often used in the context of programming languages, such as Lisp, Scheme, or Haskell, where it is used to describe a specific programming construct or idiom.

Here is an example of how a tag surrogate might be used in a programming language:

(define (square x)
  (let ((y (* x x)))
    y))  ; y is a tag surrogate for the result of the multiplication

In this example, the let expression creates a new value y that is the result of multiplying x by itself. The y value is a tag surrogate for the result of the multiplication, and it is used as the return value of the square function.