cs343 p. 23

Lisp Data

Symbols may contain letters, numerals, and some special characters + - * / @ $ % ^ & _ < > ~ . ?
```
 MASS CS343 WIDGET-ALIGNMENT-SCREW ?X
```
Numbers: floating-point, complex, integer (including bignums or big numbers), rational: 1/3.
Atoms include symbols and numbers.
S-expressions (symbolic expressions) are defined recursively as follows:
- An atom is an S-expression.
- If x₁ ... x_n are S-expressions, then (x₁ ... x_n ), called a list of x₁ ... x_n, is an S-expression.
```
ONTOGENY
(THIS IS A LIST)
(* PI (EXPT R 2))
(ALL X (IF (HUMAN X) (MORTAL X)))
()      ((()))      ((()())())
```

The empty list () is equivalent to the symbol NIL.