Welcome to pils, a simple lisp :)
example expressions: * 1 2 3 4 ( + 3 4) 0 ( / 100 3 10 ) eval { tail ( list 1 2 3 4 ) } eval (tail {tail tail {5 6 7}}) tail { tail join eval head } eval {head (list 1 2 3 4)} def {a b c} 1 2 3 def {args} {a b c} def args 4 5 6
+, -, *, / work as prefix operators on numbers and s-expressions that evaluate to numbers.
'(' and ')' create an s-expression like so: '(* 1 2 3 )' An s-expression always starts with an operator and is followed by numbers or other s-expressions.
'{' and '}' create a q-expression like so: '{ 1 2 3 tail }' A q-expression is not evaluated and can contain anything. Special operators act on q-expressions:
'head' takes the first element of a q-expression. 'tail' takes all elements of a q-expression, except the first. 'join' takes a q-expression with q-expressions inside, and creates one q-expression with their contents. 'eval' pretends a q-expression is an s-expression and evaluates it normally.
'list' creates a q-expression from an s-expression.
For a detailed reference, see: https://buildyourownlisp.com/. Thanks and credits to Daniel Holden for this brilliant resource.