nLab sugaring

Idea

In computer science and to some extent also in formal logic, sugaring refers to the modification of formal notation (syntax) into a form which is more readable for humans, thereby “sweetening” it for consumption. Syntactic sugar does not add to the functionality or expressivity of the language.

Peter Landin first used the expression ‘syntactic sugaring’ in the context of interpretations of terms in the λ-calculus (Landin64).

The reverse process to expressions in the more formal language is sometimes known as ‘desugaring’.

Examples

Example

In a set theory where classes are not “first-class objects” (for example ZFC, but not NBG), classes are only syntactic sugar and have no independent existence. For instance, if one defines a class $M \coloneqq \{ X | \varphi(X) \}$ by comprehension, then “$X \in M$” is syntactic sugar for “$\varphi(X)$”.

Example

In formal linguistics, natural language versions of formal expressions are described as ‘sugarings’ (Ranta 1994). Often there are many ways to sugar a formal expression into natural language.

Consider the type theoretic expression $\sum_{x: man} \sum_{y: donkey} (x\;owns\; y)$. Ranta (1994, p. 68) gives nine natural language sugarings for it by applying three different operations twice:

• there is a man and there is a donkey and he owns it,
• there is a man and he owns a donkey,
• there is a man and there is a donkey that he owns,
• there is a donkey and a man owns it,
• a man owns a donkey,
• there is a donkey that a man owns,
• there is a man such that there is a donkey and he owns it,
• there is a man who owns a donkey,
• there is a man such that there is a donkey that he owns.

References

• Peter Landin, The mechanical evaluation of expressions [pdf]

• Aarne Ranta, Type theory and the informal language of mathematics, TYPES ‘93: Proceedings of the international workshop on Types for proofs and programs, pp. 352–365, (pdf)

• Aarne Ranta, §1.6, §1.7, §9 in: Type-theoretical grammar, Oxford University Press (1994) [ISBN:9780198538578]

See also:

• Wikipedia, Syntactic sugar