Ben / Nujel

;; Some predicates that were simpler to do in nujel

[def number? [λ [a]
	"Return #t if a is a number"
	[or [int? a] [float? a] [vec? a]]
]]

[def empty? [λ [a]
	"Return #t if a is empty"
	[nil? a]
]]

[def last? [λ [a]
	"Return #t if a is the last pair in a list"
	[nil? [cdr a]]
]]

[def pos? [λ [a]
	"Return #t if a is positive"
	[>= a 0]
]]

[def zn? [λ [a]
	"Return #t if a is zero or negative"
	[<= a 0]
]]

[def neg? [λ [a]
	"Returns #t if a is negative"
	[< a 0]
]]

[def ineq? [λ [a b]
	"Returns #t a does not equal b"
	[not [eq? a b]]
]]

[def odd? [λ [a]
	"Predicate that returns #t if a is odd"
	[= [% [int a] 2] 1]
]]
[def even? [λ [a]
	"Predicate that returns #t if a is even"
	[= [% [int a] 2] 0]
]]

[def zero? [λ [val]
	"#t if VAL is a integer"
	[eq? 0 val]
]]

[def there-exists? [λ [l pred]
	"Applies predicate to each element and return #t if it holds true for any element, otherwise #f"
	[cond [[nil? l] #f]
	      [[pred [car l]] #t]
	      [#t [there-exists? [cdr l] pred]]
	]
]]

[def for-all? [λ [l pred]
	"Applies predicate to each element returns #t if it holds true for every element, otherwise #f"
	[cond [[nil? l] #t]
	      [[not [pred [car l]]] #f]
	      [#t [for-all? [cdr l] pred]]
	]
]]

[def int? [λ [val]
	"#t if VAL is a integer"
	[eq? :int [type-of val]]
]]

[def float? [λ [val]
	"#t if VAL is a floating-point number"
	[eq? :float [type-of val]]
]]

[def vec? [λ [val]
	"#t if VAL is a vector"
	[eq? :vec [type-of val]]
]]

[def bool? [λ [val]
	"#t if VAL is a boolean"
	[eq? :bool [type-of val]]
]]

[def inf? [λ [val]
	"#t if VAL is infinite"
	[eq? :infinity [type-of val]]
]]

[def pair? [λ [val]
	"#t if VAL is a pair"
	[eq? :pair [type-of val]]
]]

[def string? [λ [val]
	"#t if VAL is a string"
	[eq? :string [type-of val]]
]]

[def symbol? [λ [val]
	"#t if VAL is a symbol"
	[eq? :symbol [type-of val]]
]]

[def lambda? [λ [val]
	"#t if VAL is a lambda"
	[eq? :lambda [type-of val]]
]]

[def native? [λ [val]
	"#t if VAL is a native function"
	[eq? :native-function [type-of val]]
]]

[def procedure? [λ [val]
	"#t if VAL is a native or lisp function"
	[or [lambda? val] [native? val]]
]]