Symbolic data
- Racket allows one to define and use symbols with meaning to us
- A symbol is defined using an apostrophe or ‘quote’: ‘CS135
A character is most commonly a printed letter, digit, or punctuation symbol.
Modelling programming languages
- A program has a precise meaning and effect.
- A model of a programming language provides a way of describing the meaning of a program.
- This is one of the things we like about using a functional programming language! It allows us to describe easily and precisely what a program does when it’s executed.
Spelling
Identifiers are the names of constants, parameters, and user-defined functions.
They are made up of letters, numbers, hyphens, underscores, and a few other punctuation marks. They must contain at least at least one non-number. They can’t contain spaces or any of these: (),;{}[]’’””
Semantics (语义)