| 1 | """ |
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| 2 | Knuth's TPK program in Cobra |
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| 3 | |
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| 4 | From http://en.wikipedia.org/wiki/Trabb_Pardo-Knuth_algorithm |
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| 5 | |
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| 6 | "In their 1977 work "The Early Development of Programming Languages", Trabb Pardo |
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| 7 | and Knuth introduced a trivial program which involved arrays, indexing, |
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| 8 | mathematical functions, subroutines, I/O, conditionals and iteration. They then |
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| 9 | wrote implementations of the algorithm in several early programming languages to |
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| 10 | show how such concepts were expressed." |
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| 11 | |
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| 12 | While this is useful for demonstrating a few basic things about a language, it |
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| 13 | does not demonstrate well the features surrounding larger issues such as |
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| 14 | organizing large code bases, working on a team, documenting your code, etc. |
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| 15 | Also, the standard TPK code mixes input, computations and output all together. |
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| 16 | It also directly references stdin and hard codes constants rather than taking |
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| 17 | parameters for those things. |
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| 18 | |
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| 19 | But some people still like to see this code to compare it to other languages. |
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| 20 | So here it is, including a better version that addresses some of the above issues. |
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| 21 | """ |
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| 22 | |
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| 23 | class TPK |
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| 24 | |
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| 25 | shared |
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| 26 | |
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| 27 | def f(x as number) as number |
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| 28 | return x.abs.sqrt + 5.0 * x.pow(3.0) |
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| 29 | |
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| 30 | def basicTPK1 |
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| 31 | a = number[](11) |
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| 32 | |
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| 33 | # read in the values for the array, one per line |
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| 34 | for i in a.length |
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| 35 | a[i] = number.parse(Console.readLine) |
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| 36 | |
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| 37 | # in reverse order, apply "f" to each element of the array and |
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| 38 | # print the result, including index |
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| 39 | for i in a.length-1 : 0 : -1 |
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| 40 | y = .f(a[i]) |
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| 41 | print '[i] ', if(y>400, 'TOO LARGE', y) |
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| 42 | |
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| 43 | def basicTPK2 |
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| 44 | # some versions in other languages print the input number |
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| 45 | # rather than its index |
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| 46 | a = number[](11) |
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| 47 | for i in a.length |
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| 48 | a[i] = number.parse(Console.readLine) |
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| 49 | Array.reverse(a) |
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| 50 | for x in a |
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| 51 | y = .f(x) |
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| 52 | print '[x] ', if(y>400, 'TOO LARGE', y) |
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| 53 | |
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| 54 | def betterTPK |
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| 55 | """ |
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| 56 | Invokec .betterTPK with default arguments: Console.in, 11 and 400. |
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| 57 | """ |
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| 58 | .betterTPK(Console.in to !, 11, 400) |
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| 59 | |
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| 60 | def betterTPK(tr as TextReader, count as int, limit as number) |
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| 61 | require |
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| 62 | count > 0 |
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| 63 | ensure |
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| 64 | # Well there's not much to ensure for a method that dumps its |
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| 65 | # results as textual output. An even better approach is to |
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| 66 | # separate computation from I/O so that computations can be |
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| 67 | # more easily tested, contracted and reused. |
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| 68 | true |
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| 69 | test |
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| 70 | # Now that we're using parameters, we can make a proper test. |
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| 71 | sw = StringWriter() |
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| 72 | print to sw |
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| 73 | .betterTPK(StringReader('1\r\n1\r\n'), 2, 400) |
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| 74 | r = sw.toString.replace('\r','').replace('\n','; ') |
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| 75 | assert r == '1 6.0; 1 6.0; ' |
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| 76 | body |
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| 77 | a = number[](count) |
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| 78 | for i in a.length |
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| 79 | a[i] = number.parse(tr.readLine) |
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| 80 | Array.reverse(a) |
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| 81 | for x in a |
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| 82 | y = .f(x) |
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| 83 | print '[x] ', if(y>limit, 'TOO LARGE', y) |
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| 84 | |
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| 85 | def main |
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| 86 | if false |
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| 87 | print |
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| 88 | print 'Basic TPK - Enter numbers:' |
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| 89 | .basicTPK1 |
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| 90 | if true |
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| 91 | print |
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| 92 | print 'Better TPK - Enter numbers:' |
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| 93 | .betterTPK |
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