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39
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1 # 1) Fibanacci by recursion (fibr) and loop (fibl)
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2 fibr := method(num,
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3 if (num < 1,
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4 return 0,
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5 if (num == 1,
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6 return 1,
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7 prev := fibr(num - 1) ;
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8 prev_prev := fibr(num - 2) ;
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9 return prev + prev_prev
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10 )
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11 )
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12 )
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13
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14 "fibr(9) = " print
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15 fibr(9) println
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16 "fibr(4) = " print
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17 fibr(4) println
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18 "fibr(1) = " print
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19 fibr(1) println
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20
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21
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22 fibl := method(num,
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23 if (num < 1, return 0)
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24 if (num == 1, return 1)
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25 prev := 1
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26 prev_prev := 0
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27 val := 0
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28 for(i, 2, num,
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29 val = prev + prev_prev
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30 prev_prev = prev
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31 prev = val
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32 )
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33 return val
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34 )
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35
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36 "fibl(9) = " print
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37 fibl(9) println
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38 "fibl(4) = " print
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39 fibl(4) println
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40 "fibl(1) = " print
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41 fibl(1) println
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42
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43
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44 # 2) Changing "/" operator to return 0 for a zero denominator
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45 # Operators are just messages on objects, so "/" is the message to override
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46 # and it must be on the object type Number
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47 Number defaultDivide := Number getSlot("/")
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48 Number / := method(denom,
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49 if (denom == 0,
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50 return 0,
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51 return self defaultDivide(denom))
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52 )
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53 (4 / 2) println
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54 (4 / 0) println
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55
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56
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57 # 3) Add up numbers in a 2D array
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58 arr := list(
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59 list(1, 2, 3),
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60 list(4, 5, 6),
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61 list(7, 8, 9)
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62 )
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63
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64 add2D := method(arr,
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65 sum := 0
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66 # A "reduce()" method would be nice, but KISS for now and foreach all the things
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67 arr foreach(dimension, dimension foreach(val, sum = sum + val))
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68 return sum
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69 )
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70
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71 add2D(arr) println
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72
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73
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74 # 4) Add myAverage to average numbers in a list
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75 List myAverage := method(
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76 sum := 0
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77 self foreach(val, if (val proto == Number,
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78 sum = sum + val,
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79 Exception raise("Non-object found in list"))
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80 )
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81 return sum / self size
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82 )
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83
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84 list(1, 2, 3) myAverage println
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85 # This will exception - run at the end!
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86 # list(1, 2, 3, "foo") myAverage
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87 # With default behaviour then this could divide by zero (unless we'd been defensive coding)
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88 # But we're in the same file as our custom "/", so we should get zero
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89 list() myAverage println
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90
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91
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40
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92 #5) 2D list
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93 TwoDList := Object clone
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94 # It'd be nice to do something to set defaults when first cloning
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95 # but I can't find how to do that, so force the developer to
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96 # always dim() after clone
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97 TwoDList dim := method(x, y,
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98 self arr := list()
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99 for (i, 1, x,
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100 sub_list := list()
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101 for (j, 1, y,
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102 sub_list append(nil)
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103 )
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104 arr append(sub_list)
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105 )
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106 )
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107 TwoDList set := method(x, y, value,
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108 self arr at(x) atPut(y, value)
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109 )
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110
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111 TwoDList get := method(x, y,
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112 outer := self arr at(x)
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113 if (outer != nil,
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114 return outer at(y),
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115 return nil
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116 )
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117 )
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118
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119 my_arr := TwoDList clone
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120 my_arr dim(2, 3)
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121 my_arr println
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122 my_arr set(0, 1, "0,1")
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123 my_arr set(1, 2, "Bottom-right")
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124 my_arr get(1, 2) println
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125 my_arr get(0, 1) println
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126 my_arr get(0, 0) println
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127 my_arr get(5, 5) println
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128
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129
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130
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131 # 4) final piece
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39
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132 list(1, 2, 3, "foo") myAverage |
