{"id":60,"date":"2007-05-31T12:39:39","date_gmt":"2007-05-31T17:39:39","guid":{"rendered":"http:\/\/www.pixelwit.com\/blog\/2007\/05\/31\/how-to-limit-a-number-between-2-values\/"},"modified":"2009-08-13T21:20:38","modified_gmt":"2009-08-14T02:20:38","slug":"how-to-limit-a-number-between-2-values","status":"publish","type":"post","link":"https:\/\/www.pixelwit.com\/blog\/2007\/05\/31\/how-to-limit-a-number-between-2-values\/","title":{"rendered":"How to Limit a Number Between 2 Values"},"content":{"rendered":"

Limiting or constraining a number to a specified range of values isn’t the most common task you’ll have to perform in Flash, but it does pop up from time to time. If you encounter such a situation here is a little bit of code for your consideration:<\/p>\n

\/\/<\/span>
\n\/\/ Basic concept, easy to extend.<\/span>
\nfunction<\/span> limitBasic (<\/span>num, lo, hi)<\/span>{<\/span>
\n    if<\/span> (<\/span>num<<\/span>lo)<\/span>{<\/span>
\n        return<\/span> lo;
\n    }<\/span>else<\/span> if<\/span>(<\/span>num><\/span>hi)<\/span>{<\/span>
\n        return<\/span> hi;
\n    }<\/span>else<\/span>{<\/span>
\n        return<\/span> num;
\n    }<\/span>
\n}<\/span>
\n\/\/<\/span>
\n\/\/ Same concept, easy to remember and write.<\/span>
\nfunction<\/span> limitShort (<\/span>num, lo, hi)<\/span>{<\/span>
\n    if<\/span> (<\/span>num<<\/span>lo)<\/span> return<\/span> lo;
\n    if<\/span> (<\/span>num><\/span>hi)<\/span> return<\/span> hi;
\n    return<\/span> num;
\n}<\/span>
\n\/\/<\/span>
\n\/\/ Same concept, short but hard to read.<\/span>
\nfunction<\/span> limitTiny (<\/span>num, lo, hi)<\/span>{<\/span>
\n    return<\/span> num<<\/span>lo ? lo : num><\/span>hi ? hi : num;
\n}<\/span>
\n\/\/<\/span>
\n\/\/ Uses the Math object, short but a little counterintuitive and slow.<\/span>
\nfunction<\/span> limitSlow (<\/span>num, lo, hi)<\/span>{<\/span>
\n    return<\/span> Math<\/span>.min<\/span>(<\/span>hi, Math<\/span>.max<\/span>(<\/span>lo, num)<\/span>)<\/span>;
\n}<\/span>
\n\/\/<\/span>
\n\/\/<\/span><\/div><\/div>\n

All four functions work the same basic way.<\/p>\n

    \n
  • If the number (“num”) is below the lower limit (“lo”), it is set to the lower limit.<\/li>\n
  • If the number is above the upper limit (“hi”) it is set to the upper limit.<\/li>\n
  • If the number is between or within both limits, it remains unchanged.<\/li>\n<\/ul>\n

    The main thing to note is that the “limitSlow” function uses the Math object which makes it a good bit slower than the other limiting methods. The other three “limit” or “constrain” functions are fundamentally the same in performance and concept but the structure of the conditional statements has been changed to suit different coding styles. If you’re not sure which one is best, use “limitBasic” as it is the most common format for “if else” conditional statements and therefore easier for most people to read.<\/p>\n

    Here’s a code sample to get you started:<\/p>\n

    \/\/<\/span>
    \n\/\/ Limit a number between two values.<\/span>
    \nfunction<\/span> limit (<\/span>num, lo, hi)<\/span>{<\/span>
    \n    if<\/span> (<\/span>num<<\/span>lo)<\/span>{<\/span>
    \n        return<\/span> lo;
    \n    }<\/span>else<\/span> if<\/span>(<\/span>num><\/span>hi)<\/span>{<\/span>
    \n        return<\/span> hi;
    \n    }<\/span>else<\/span>{<\/span>
    \n        return<\/span> num;
    \n    }<\/span>
    \n}<\/span>
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/ Build Description textfields.<\/span>
    \ncreateTextField<\/span>(<\/span>"LoDescTF"<\/span>, 10<\/span>, 50<\/span>, 10<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nLoDescTF.text<\/span> = "Lower Limit"<\/span>;
    \n\/\/<\/span>
    \ncreateTextField<\/span>(<\/span>"LimitedDescTF"<\/span>, 20<\/span>, 200<\/span>, 10<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nLimitedDescTF.text<\/span> = "Limited Value"<\/span>;
    \n\/\/<\/span>
    \ncreateTextField<\/span>(<\/span>"HiDescTF"<\/span>, 30<\/span>, 350<\/span>, 10<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nHiDescTF.text<\/span> = "Upper Limit"<\/span>;
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/ Build User-input textfields.<\/span>
    \ncreateTextField<\/span>(<\/span>"LoTF"<\/span>, 11<\/span>, 50<\/span>, 30<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nLoTF.type<\/span> = "input"<\/span>;
    \nLoTF.border<\/span> = true<\/span>;
    \nLoTF.restrict<\/span> = "0-9"<\/span>;
    \nLoTF.text<\/span> = "0"<\/span>;
    \n\/\/<\/span>
    \ncreateTextField<\/span>(<\/span>"LimitedTF"<\/span>, 21<\/span>, 200<\/span>, 30<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nLimitedTF.type<\/span> = "input"<\/span>;
    \nLimitedTF.border<\/span> = true<\/span>;
    \nLimitedTF.restrict<\/span> = "0-9"<\/span>;
    \nLimitedTF.text<\/span> = "50"<\/span>;
    \n\/\/<\/span>
    \ncreateTextField<\/span>(<\/span>"HiTF"<\/span>, 31<\/span>, 350<\/span>, 30<\/span>, 100<\/span>, 20<\/span>)<\/span>;
    \nHiTF.type<\/span> = "input"<\/span>;
    \nHiTF.border<\/span> = true<\/span>;
    \nHiTF.restrict<\/span> = "0-9"<\/span>;
    \nHiTF.text<\/span> = "100"<\/span>;
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/ Build Instructions textfield.<\/span>
    \ncreateTextField<\/span>(<\/span>"Instructions"<\/span>, 40<\/span>, 10<\/span>, 60<\/span>, 480<\/span>, 40<\/span>)<\/span>;
    \nInstructions.wordWrap<\/span> = true<\/span>;
    \nInstructions.multiline<\/span> = true<\/span>;
    \nInstructions.text<\/span> = "Type a number in the middle box and press the enter key to limit the number between the low and high values."<\/span>;
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/<\/span>
    \n\/\/ Limit the value in the middle box when the Enter key is pressed.<\/span>
    \nLimitedTF.onKeyDown<\/span> = function<\/span>(<\/span>)<\/span>{<\/span>
    \n    if<\/span>(<\/span>Key<\/span>.isDown<\/span>(<\/span>Key<\/span>.ENTER<\/span>)<\/span>)<\/span>{<\/span>
    \n        var<\/span> lo = LoTF.text<\/span> - 0<\/span>;
    \n        var<\/span> hi = HiTF.text<\/span> - 0<\/span>;
    \n        var<\/span> lim = this<\/span>.text<\/span> - 0<\/span>;
    \n        this<\/span>.text<\/span> = limit(<\/span>lim, lo, hi)<\/span>;
    \n    }<\/span>
    \n}<\/span>
    \nKey<\/span>.addListener<\/span>(<\/span>LimitedTF)<\/span>;
    \n\/\/<\/span>
    \n\/\/<\/span><\/div><\/div>\n

    The above code produces the following SWF:<\/p>\n\n\n\t\n\t\n\t\n\t\n\t\t\n\t\n\t<\/object>\n\t\n<\/object>\n","protected":false},"excerpt":{"rendered":"

    An ActionScript tutorial examining various techniques used to limit a number between two values.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[8],"tags":[23,36,37],"class_list":["post-60","post","type-post","status-publish","format-standard","hentry","category-flash","tag-actionscript","tag-swfs","tag-tutorial"],"_links":{"self":[{"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/posts\/60","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/comments?post=60"}],"version-history":[{"count":0,"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/posts\/60\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/media?parent=60"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/categories?post=60"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.pixelwit.com\/blog\/wp-json\/wp\/v2\/tags?post=60"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}