The prelude

The prelude is written in the language itself and evaluated before every file. Its names need no require. A module may define its own binding with a prelude name without changing anyone else's; an unbound symbol falls back to the prelude by name. Special forms are not part of it; see special forms.

Control macros

form	expands to
(when test body...)	(if test (progn body...) nil)
(unless test body...)	(if test nil (progn body...))
(cond (test body...)... (true body...))	nested ifs; a clause with no body returns its test's value
(and x...)	the last value when every one is true, else the first false one; (and) is true
(or x...)	the first true value, else the last one; (or) is nil

and, or and cond bind their tests to gensyms, so each is evaluated once.

Threading

form	meaning
(-> x (f a) g)	(g (f x a)): the value goes into the first position
(->> x (f a) g)	(g (f a x)): the value goes into the last position

(-> x norm1 attn (+ x))         ; (+ (attn (norm1 x)) x)
(->> (range 4) (map inc) (reduce + 0)) ; 10

Functions

function	result
(inc x) (dec x)	x plus or minus one
(second xs)	(first (rest xs))
(last xs)	the last element
(zip xs ys)	a list of two-element lists, up to the shorter length

Macro helpers

form	meaning
(with-gensyms (name...) body...)	binds each name to a fresh symbol
(once-only (arg...) body...)	in a macro, evaluate each argument once, in order
(defmacro/g! name ll body...)	every g!name in the body is a fresh symbol per expansion (the Let Over Lambda convention)

See macros and symbols.

Place macros

form	expands to
(incf name [amount])	(setq name (+ name amount)), amount 1 by default
(decf name [amount])	(setq name (- name amount))
(push value name)	(setq name (cons value name))

They take variable names, not generalized places.

Not in the prelude

truthy is a builtin; dotimes and dolist are special forms. The neural network and optimizer definitions are in the standard modules sexpgpu/nn and sexpgpu/optim, which need a require.

Related: builtins, It is Common Lisp.