[ת]ΪʲôÎÒÃÇҪѧϰHaskellÕâÑùµÄ±à³ÌÓïÑÔ
תÍ⿯ITÆÀÂÛ£ºÎªÊ²Ã´ÎÒÃÇҪѧϰHaskellÕâÑùµÄ±à³ÌÓïÑÔ
ժ¼£º
¸ß½×º¯Êý(Higher Order Functions)
ÔÚHaskellÓïÑÔÖУ¬×î¶àµÄ±»·´¸´Ê¹Óõĺ¯Êý¶¼ÊǸ߽׺¯Êý(higher order functions)¡ª¡ªÄÜÒÔº¯Êý×÷Ϊ²ÎÊý¡¢ÄÜ·µ»Øº¯ÊýµÄº¯Êý¡£ÕâʹµÃËüÃǾßÓйÌÓеÄÁé»îÐÔ¡£ÏÂÃæÊÇÒ»¸ö²»Ì«Áé»îµÄº¯Êý£ºËü¼ÆËãÒ»¸öÊý×éÀïµÈÓÚij¸öÖµµÄÔªËصĸöÊý¡£
// ²»Áé»î
function countMatching(array, value) {
var counted = 0
for (var i = 0; i < array.length; i++) {
if (array[i] == value)
counted++
}
return counted
}
// == 2
countMatching([1,3,3,4,5], 3)
Ëü²»Áé»î£¬ÒòΪËüÖ»ÄÜÓÃÀ´¼ÆËãÒ»¸öÊý×éÖо«È·Æ¥Åäij¸öÖµµÄÔªËصĸöÊý¡£
ÏÂÃæÊÇÒ»¸öÁé»îһЩµÄ°æ±¾£¬ËüÄܽÓÊÜÒ»¸öº¯Êý£¬¶ø²»ÊÇÒ»¸öÖµ£¬×÷Ϊ²ÎÊý¡£ÎÒÃÇ¿ÉÒÔÓÃËüÀ´¶ÔÈκÎÊý¾Ý¡¢ÈκζÔÏó½øÐбȽϡ£
// more flexible
function count(array, matching) {
var counted = 0
for (var i = 0; i < array.length; i++) {
if (matching(array[i]))
counted++
}
return counted
}
// == 2, same as first example
count([1,3,3,4,5], function(num) {
return (num == 3)
})
// == 2, now we can use our functions for ANY kind of items or match test!
count([{name:"bob"}, {name:"henry"}, {name:"jon"}], function(obj) {
return (obj.name.length < 4)
})
ÒòΪ¸ß½×º¯Êý¸ü¾ßÁé»îÐÔ£¬Äã¾Í¸üÉÙÓлú»áȥдËüÃÇ£¬ÒòΪÄãÒ»µ©Äãд³ÉÒ»¸ö£¬Äã¿ÉÒÔËüÓ¦Óõ½¸÷ÖÖ²»Í¬µÄÇé¿öÖС£