few more problems from "99 problems" series.

MoeOrganization · Apr 23, 2013 · 2217345 · 2217345
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diff --git a/spec/examples/99-problems/17.mo b/spec/examples/99-problems/17.mo
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+# P17 (*) Split a list into two parts.
+#     The length of the first part is given.
+
+#     Example:
+
+#     moe> split_list(3, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"])
+#     [["a", "b", "c"], ["d", "e", "f", "g", "h", "i", "j", "k"]]
+
+sub split_list($n, @list) {
+    # XXXX: the range expressions should work without enclosing parens too!
+    [@list[0..($n-1)], @list[$n..(@list.length-1)]]
+}
+
+say split_list(3, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"]);
+
diff --git a/spec/examples/99-problems/18.mo b/spec/examples/99-problems/18.mo
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+# P18 (**) Extract a slice from a list.
+#     Given two indices, I and K, the slice is the list containing the
+#     elements from and including the Ith element up to but not
+#     including the Kth element of the original list. Start counting
+#     the elements with 0.
+
+#     Example:
+
+#     moe> slice(3, 7, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"])
+#     ["d", "e", "f", "g"]
+
+sub slice_list($s, $e, @list) {
+    # XXXX: the range operand without enclosing parens should work too!
+    @list[$s .. ($e-1)]
+}
+say slice_list(3, 7, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"]);
diff --git a/spec/examples/99-problems/19.mo b/spec/examples/99-problems/19.mo
@@ -0,0 +1,18 @@
+# P19 (**) Rotate a list N places to the left.
+#     Examples:
+
+#     moe> rotate(3, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"])
+#     ["d", "e", "f", "g", "h", "i", "j", "k", "a", "b", "c""]
+
+#     moe> rotate(-2, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"])
+#     ["j", "k", "a", "b", "c", "d", "e", "f", "g", "h", "i"]
+
+sub rotate($n, @list) {
+    my $len = @list.length;
+    my @r = @list[($n < 0 ? $len + $n : $n) .. ($len - 1)];
+    @r.push(@list[0 .. ($n < 0 ? $len + $n : $n-1)]);
+    @r.flatten
+}
+
+say rotate(3, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"]);
+say rotate(-2, ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"]);
diff --git a/spec/examples/99-problems/20.mo b/spec/examples/99-problems/20.mo
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+# P20 (*) Remove the Kth element from a list.
+#     Return the list and the removed element in a Tuple. Elements are numbered from 0.
+
+#     Example:
+
+#     moe> remove_at(1, ['a', 'b', 'c', 'd'])
+#     [['a', 'c', 'd'],'b']
+
+sub remove_at($i, @list) {
+    my $removed = @list[$i];
+    my @rest = @list[0 .. ($i-1)];
+    @rest.push(@list[($i+1) .. (@list.length-1)]);
+    [@rest.flatten, $removed]
+}
+
+say remove_at(1, ['a', 'b', 'c', 'd']);
diff --git a/spec/examples/99-problems/21.mo b/spec/examples/99-problems/21.mo
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+# P21 (*) Insert an element at a given position into a list.
+#     Example:
+
+#     moe> insert_at('new', 1, ['a', 'b', 'c', 'd'])
+#     ['a', 'new', 'b', 'c', 'd')
+
+sub insert_at($new, $at, @list) {
+    my @r = @list[0 .. ($at-1)];
+    @r.push($new, @list[$at .. (@list.length-1)]);
+    @r.flatten
+}
+
+say insert_at('new', 1, ['a', 'b', 'c', 'd'])
diff --git a/spec/examples/99-problems/22.mo b/spec/examples/99-problems/22.mo
@@ -0,0 +1,10 @@
+# P22 (*) Create a list containing all integers within a given range.
+#     Example:
+
+#     moe> range(4, 9)
+#     [4, 5, 6, 7, 8, 9]
+
+sub range($start, $end) { $start .. $end }
+
+say range(4, 9)
+