On this page:
list?
null?
number?
zero?
one?
eq?
equal?
symbol?
string?
fn?
atom?
lat?
and
or
not
else
True
False
Null

3.3 Predicates and Logic

procedure

(list? v)  boolean?

  v : any
Returns True if v is a list.

procedure

(null? v)  boolean?

  v : any
Returns True if v is Null, where Null is defined as the empty list '().

procedure

(number? v)  boolean?

  v : any
Returns True if v is a number.

procedure

(zero? v)  boolean?

  v : any
Returns True if v = 0.

procedure

(one? v)  boolean?

  v : any
Returns True if v = 1.

procedure

(eq? x y)  boolean?

  x : any
  y : any
Returns True if x and y are the same object.

procedure

(equal? x y)  boolean?

  x : any
  y : any
Returns True if x and y are equal.

procedure

(symbol? v)  boolean?

  v : any
Returns True if v is a symbol: ie. a quoted name such as 'foo. See quote in Syntax and Evaluation.

procedure

(string? v)  boolean?

  v : any
Returns True if v is a string.

procedure

(fn? v)  boolean?

  v : any
Returns True if v is a function.

procedure

(atom? v)  boolean?

  v : any
Returns True if v is an atom: ie. a number, symbol, or function, rather than a list or Null.

procedure

(lat? l)  boolean?

  l : any
Returns True if l is a list composed solely of atoms.

syntax

(and expr ...)

Returns True only if all given expressions are True.

syntax

(or expr ...)

Returns True if any given expression is True.

procedure

(not v)  boolean?

  v : any
Returns True if v is False, else returns False.

syntax

else

A special keyword for True, used as a literal in conditional statements.

value

True : boolean?

The boolean truth value. Actually an alias for #t in the Racket implementation. Note that, in Heresy, as in Racket, anything not explicitly False is considered True.

value

False : boolean?

The boolean false value. Actually an alias for #f in the Racket implementation.

value

Null : null?

An alias for the empty list '().