(namespace core)
(docs "predicate to test for equality with zero"
      tags [numbers]
      example: (zero? n))
(macro zero? (item) '(= @item 0))


(docs "returns true if the array `arr` has a length of zero"
      tags [arrays collections]
      example: (empty? []))
(macro empty? (arr)
       `(= 0 (length @arr)))


(docs "returns true if `number` is not divisible by 2"
      tags [numbers]
      example (odd? 5))
(macro odd? (number)
       '(= 1 (mod @number 2)))


(docs "returns true if `number` is divisible by 2 with no remainder"
      tags [numbers]
      example (even? 10))
(macro even? (number)
       '(= 0 (mod @number 2)))
(docs "returns true if all of the `things` are javascript strings"
      tags [strings type]
      examples: [ (string? test-object) (string? 'yes 'yes 'yes) ])
(macro string? (...things)
       '(and ...@(map things (#(thing) '(= (typeof @thing) 'string)))))


(docs "returns true if all of the `things` are functions"
      tags [functions type]
      examples: [ (function? fn) (function? err cb) ])
(macro function? (...things)
       '(and ...@(map things (#(thing) '(= (typeof @thing) 'function)))))
(docs "returns true if all of the `things` are undefined, as tested
with `typeof`, not equality with literal undefined. This is the
inverse of `defined?`"
      tags [type]
      examples: [ (undefined? argument)
                  (undefined? 1 2 undefined) ])
(macro undefined? (...things)
       '(and ...@(map things (#(thing) '(= (typeof @thing) 'undefined)))))

(docs "returns true if none of the `things` are undefined, as tested
with `typeof`. This is the inverse of `undefined?`"
      tags [type]
      examples: [ (defined? variable)
                  (defined? var1 var2 var3) ])
(macro defined? (...things)
       '(and ...@(map things (#(thing) '(!= (typeof @thing) 'undefined)))))


(docs "returns true if all of the `things` are numbers, as tested
with `typeof`"
      tags [numbers type]
      examples: [ (number? 1) (number? 1 2 3) ])
(macro number? (...things)
       '(and ...@(map things (#(thing) '(= (typeof @thing) 'number)))))


(docs "returns true if `thing` is an array in javascript. aliased as
`list?`."
      tags [type arrays]
      example: (array? arr))

(macro array? (thing)
       `(and
         @thing
         (= 'object (typeof @thing))
         (= 'Array (get @thing 'constructor 'name))))
(alias-macro array? list?)


(docs "returns true if `thing` is an object that is not an array in javascript. aliased as
`object?`."
      tags [type objects]
      example: (object? arr))

(macro hash? (thing)
       `(and (= 'object (typeof @thing))
             (!= @thing null)
             (!= (get @thing 'constructor 'name) 'Array)))
(alias-macro hash? object?)


(docs "uses the javascript `instanceof` operator to check if `item` is of `type`."
      tags [language type]
      example (instance-of? (new Date) Date))
(macro instance-of? (item type)
       `(parens (transpile item) " instanceof " (transpile type)))



(docs "similar to the javascript truthiness predicate `as-boolean`, returns true unless the `thing` is undefined or null"
      tags [type]
      example (exists? window))
(macro exists? (thing)
       `(and (defined? @thing) (!= @thing null)))


(docs "checks if `object` has property `key`.  returns true or false."
      tags [objects collections]
      example (has-key? object 'a))

(macro has-key? (object key)
       `(.has-own-property @object @key))

(docs "checks if a string is identical to the lower-cased version of itself"
      tags [strings]
      example (lower-case? "abc"))
(macro lower-case? (str)
       `(and
         (!= (.to-upper-case @str) @str)
         (= (.to-lower-case @str) @str)))



(docs "checks if a string is identical to the upper-cased version of itself"
      tags [strings]
      example (lower-case? "abc"))
(macro upper-case? (str)
       `(and
         (!= (.to-lower-case @str) @str)
         (= (.to-upper-case @str) @str)))