Implementing a Measured value in Scala -


a measured value consists of (typically nonnegative) floating-point number , unit-of-measure. point represent real-world quantities, , rules govern them. here's example:

scala> val oneinch = measure(1.0, inch) oneinch : measure[inch] = measure(1.0) scala> val twoinch = measure(2.0, inch) twoinch : measure[inch] = measure(2.0) scala> val onecm = measure(1.0, cm) onecm : measure[cm] = measure(1.0) scala> oneinch + twoinch res1: measure[inch] = measure(3.0) scala> oneinch + onecm res2: measure[inch] = measure(1.787401575) scala> onecm * onecm res3: measure[cmsq] = measure(1.0) scala> onecm * oneinch res4: measure[cmsq] = measure(2.54) scala> oncem * measure(1.0, liter) console>:7: error: conformance mismatch scala> oneinch * 2 == twoinch res5: boolean = true

before excited, haven't implemented this, dummied repl session. i'm not sure of syntax, want able handle things adding measured quantities (even mixed units), multiplying measured quantities, , on, , ideally, scala's vaunted type-system guarantee @ compile-time expressions make sense.

my questions:

  1. is there extant terminology problem?
  2. has been done in scala?
  3. if not, how represent concepts "length" , "length measured in meters"?
  4. has been done in other language?

a $330-million mars probe lost because contractor using yards , pounds , nasa using meters , newtons. measure library have prevented crash.

well, functionality exists in java, meaning can use directly in scala.

jsr-275, moved google code. jscience implements spec. here's introduction. if want better interface, i'd use base , build wrapper around it.


Comments

Post a Comment

Popular posts from this blog

asp.net - repeatedly call AddImageUrl(url) to assemble pdf document -

i'm using abcpdf , i'm curious if can recursively call addimageurl() function assemble pdf document compile multiple urls? something like: int pagecount = 0; int theid = thedoc.addimageurl("http://stackoverflow.com/search?q=abcpdf+footer+page+x+out+of+", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetochain(theid); } pagecount = thedoc.pagecount; console.writeline("1 document page count:" + pagecount); //flatten document (int = 1; <= pagecount; i++) { thedoc.pagenumber = i; thedoc.flatten(); } //now try again theid = thedoc.addimageurl("http://stackoverflow.com/questions/1980890/pdf-report-generation", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetoc
Read more

java - Android recognize cell phone with keyboard or not? -

in android app, want detect user's device if device has keyboard(like motorola milestone) , show corresponding user interface. guys know how that? ! regards justicepenny http://developer.android.com/reference/android/content/res/configuration.html public int keyboard the kind of keyboard attached device. 1 of: keyboard_nokeys, keyboard_qwerty, keyboard_12key. that's it!
Read more

iphone - How would you achieve a LED Scrolling effect? -

how achieve led scrolling effect example below? led sign - led ticker emulator iphone , ipad http://img.skitch.com/20101201-rsfh4p1bajb1wp94k466pdpiuj.preview.jpg sometimes remunerates comment in other posts :) have put code you, should implement font '8pin matrix' realistic feeling. uilabel *label; - (void)viewdidload { [super viewdidload]; label = [[uilabel alloc]initwithframe:cgrectmake(10, 50, 300, 20)]; label.font = [uifont fontwithname:@"courier-bold" size:16.0]; label.backgroundcolor = [uicolor blackcolor]; label.textcolor = [uicolor greencolor]; label.linebreakmode = uilinebreakmodecharacterwrap; // otherwise "…" label.text = @"this led text scrolled "; // blanks space between [self.view addsubview:label]; [nstimer scheduledtimerwithtimeinterval:0.12f target:self selector:@selector(scrolllabel) use
Read more