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Howto:Start using vectors and hashes in Nasal: Difference between revisions
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Howto:Start using vectors and hashes in Nasal (view source)
Revision as of 22:43, 3 June 2014
, 3 June 2014→Learn more about vectors: https://gitorious.org/fg/fgdata/source/55a9523d833a9c65bab431e2cffcf99d09c78dd4:Aircraft/777/Nasal/efb.nas#L137-1890
m (→A hash based version (recommended): http://forum.flightgear.org/viewtopic.php?f=71&t=23204&p=211634#p211629) |
m (→Learn more about vectors: https://gitorious.org/fg/fgdata/source/55a9523d833a9c65bab431e2cffcf99d09c78dd4:Aircraft/777/Nasal/efb.nas#L137-1890) |
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Just imagine we'd need to support more than just 5 waypoints, like maybe 10, 20, 50 or maybe even 1000 waypoints. As you can see, this method is very inflexible, complicated, tedious and error-prone. | Just imagine we'd need to support more than just 5 waypoints, like maybe 10, 20, 50 or maybe even 1000 waypoints. As you can see, this method is very inflexible, complicated, tedious and error-prone. | ||
Such code contains so called "code smells", another example would be code like this: | |||
<syntaxhighlight lang="php"> | |||
var l0 = ""; | |||
var l1 = ""; | |||
var l2 = ""; | |||
var l3 = ""; | |||
var l4 = ""; | |||
var l5 = ""; | |||
var l6 = ""; | |||
var l7 = ""; | |||
var l8 = ""; | |||
var l9 = ""; | |||
var l10 = ""; | |||
var l11 = ""; | |||
var l12 = ""; | |||
var l13 = ""; | |||
var l14 = ""; | |||
var l15 = ""; | |||
var l16 = ""; | |||
var l17 = ""; | |||
var l18 = ""; | |||
var l19 = ""; | |||
var l20 = ""; | |||
var hist1 = ""; | |||
var hist2 = ""; | |||
var hist3 = ""; | |||
var hist4 = ""; | |||
var hist5 = ""; | |||
var hist6 = ""; | |||
IDENTl3 = ""; | |||
IDENTl4 = ""; | |||
IDENTr4 = ""; | |||
IDENTl5 = ""; | |||
IDENTr5 = ""; | |||
IDENTl8 = ""; | |||
setprop("/instrumentation/efb/display/line0-l", l0); | |||
setprop("/instrumentation/efb/display/line1-l", l1); | |||
setprop("/instrumentation/efb/display/line2-l", l2); | |||
setprop("/instrumentation/efb/display/line3-l", l3); | |||
setprop("/instrumentation/efb/display/line4-l", l4); | |||
setprop("/instrumentation/efb/display/line5-l", l5); | |||
setprop("/instrumentation/efb/display/line6-l", l6); | |||
setprop("/instrumentation/efb/display/line7-l", l7); | |||
setprop("/instrumentation/efb/display/line8-l", l8); | |||
setprop("/instrumentation/efb/display/line9-l", l9); | |||
setprop("/instrumentation/efb/display/line10-l", l10); | |||
setprop("/instrumentation/efb/display/line11-l", l11); | |||
setprop("/instrumentation/efb/display/line12-l", l12); | |||
setprop("/instrumentation/efb/display/line13-l", l13); | |||
setprop("/instrumentation/efb/display/line14-l", l14); | |||
setprop("/instrumentation/efb/display/line15-l", l15); | |||
setprop("/instrumentation/efb/display/line16-l", l16); | |||
setprop("/instrumentation/efb/display/line17-l", l17); | |||
setprop("/instrumentation/efb/display/line18-l", l18); | |||
setprop("/instrumentation/efb/display/line19-l", l19); | |||
setprop("/instrumentation/efb/display/line20-l", l20); | |||
</syntaxhighlight> | |||
Whenever you see such code, it should be obvious that using arrays/vectors would be a good idea. | |||
So, it would be better to use a vector of waypoints instead. A vector is a list of things (variables) that can be easily accessed using an index into the vector. Pretty much like an array in C or C++, with the added advantage that the vector can be dynamically resized, e.g. using the setsize() library call. Consider the following example: | So, it would be better to use a vector of waypoints instead. A vector is a list of things (variables) that can be easily accessed using an index into the vector. Pretty much like an array in C or C++, with the added advantage that the vector can be dynamically resized, e.g. using the setsize() library call. Consider the following example: | ||