1lsort(n) Tcl Built-In Commands lsort(n)
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8 lsort - Sort the elements of a list
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11 lsort ?options? list
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15 This command sorts the elements of list, returning a new list in sorted
16 order. The implementation of the lsort command uses the merge-sort
17 algorithm which is a stable sort that has O(n log n) performance char‐
18 acteristics.
19 By default ASCII sorting is used with the result returned in increasing
21 order. However, any of the following options may be specified before
22 list to control the sorting process (unique abbreviations are
23 accepted):
24 -ascii Use string comparison with Unicode code-point collation order
26 (the name is for backward-compatibility reasons.) This is the
27 default.
28 -dictionary
30 Use dictionary-style comparison. This is the same as -ascii
31 except (a) case is ignored except as a tie-breaker and (b) if
32 two strings contain embedded numbers, the numbers compare as
33 integers, not characters. For example, in -dictionary mode,
34 bigBoy sorts between bigbang and bigboy, and x10y sorts between
35 x9y and x11y. Overrides the -nocase option.
36 -integer
38 Convert list elements to integers and use integer comparison.
39 -real Convert list elements to floating-point values and use floating
41 comparison.
42 -command command
44 Use command as a comparison command. To compare two elements,
45 evaluate a Tcl script consisting of command with the two ele‐
46 ments appended as additional arguments. The script should
47 return an integer less than, equal to, or greater than zero if
48 the first element is to be considered less than, equal to, or
49 greater than the second, respectively.
50 -increasing
52 Sort the list in increasing order (“smallest”items first). This
53 is the default.
54 -decreasing
56 Sort the list in decreasing order (“largest”items first).
57 -indices
59 Return a list of indices into list in sorted order instead of
60 the values themselves.
61 -index indexList
63 If this option is specified, each of the elements of list must
64 itself be a proper Tcl sublist (unless -stride is used).
65 Instead of sorting based on whole sublists, lsort will extract
66 the indexList'th element from each sublist (as if the overall
67 element and the indexList were passed to lindex) and sort based
68 on the given element. For example,
69 lsort -integer -index 1 \
71 {{First 24} {Second 18} {Third 30}}
72 returns {Second 18} {First 24} {Third 30},
74 lsort -index end-1 \
76 {{a 1 e i} {b 2 3 f g} {c 4 5 6 d h}}
77 returns {c 4 5 6 d h} {a 1 e i} {b 2 3 f g}, and
79 lsort -index {0 1} {
81 {{b i g} 12345}
82 {{d e m o} 34512}
83 {{c o d e} 54321}
84 }
85 returns {{d e m o} 34512} {{b i g} 12345} {{c o d e} 54321}
87 (because e sorts before i which sorts before o.) This option is
88 much more efficient than using -command to achieve the same
89 effect.
90 -stride strideLength
92 If this option is specified, the list is treated as consisting
93 of groups of strideLength elements and the groups are sorted by
94 either their first element or, if the -index option is used, by
95 the element within each group given by the first index passed to
96 -index (which is then ignored by -index). Elements always remain
97 in the same position within their group.
98 The list length must be an integer multiple of strideLength,
100 which in turn must be at least 2.
101 For example,
103 lsort -stride 2 {carrot 10 apple 50 banana 25}
105 returns “apple 50 banana 25 carrot 10”, and
107 lsort -stride 2 -index 1 -integer {carrot 10 apple 50 banana 25}
109 returns “carrot 10 banana 25 apple 50”.
111 -nocase
113 Causes comparisons to be handled in a case-insensitive manner.
114 Has no effect if combined with the -dictionary, -integer, or
115 -real options.
116 -unique
118 If this option is specified, then only the last set of duplicate
119 elements found in the list will be retained. Note that dupli‐
120 cates are determined relative to the comparison used in the
121 sort. Thus if -index 0 is used, {1 a} and {1 b} would be con‐
122 sidered duplicates and only the second element, {1 b}, would be
123 retained.
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126 The options to lsort only control what sort of comparison is used, and
127 do not necessarily constrain what the values themselves actually are.
128 This distinction is only noticeable when the list to be sorted has
129 fewer than two elements.
130 The lsort command is reentrant, meaning it is safe to use as part of
132 the implementation of a command used in the -command option.
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135 Sorting a list using ASCII sorting:
136 % lsort {a10 B2 b1 a1 a2}
138 B2 a1 a10 a2 b1
139 Sorting a list using Dictionary sorting:
141 % lsort -dictionary {a10 B2 b1 a1 a2}
143 a1 a2 a10 b1 B2
144 Sorting lists of integers:
146 % lsort -integer {5 3 1 2 11 4}
148 1 2 3 4 5 11
149 % lsort -integer {1 2 0x5 7 0 4 -1}
150 -1 0 1 2 4 0x5 7
151 Sorting lists of floating-point numbers:
153 % lsort -real {5 3 1 2 11 4}
155 1 2 3 4 5 11
156 % lsort -real {.5 0.07e1 0.4 6e-1}
157 0.4 .5 6e-1 0.07e1
158 Sorting using indices:
160 % # Note the space character before the c
162 % lsort {{a 5} { c 3} {b 4} {e 1} {d 2}}
163 { c 3} {a 5} {b 4} {d 2} {e 1}
164 % lsort -index 0 {{a 5} { c 3} {b 4} {e 1} {d 2}}
165 {a 5} {b 4} { c 3} {d 2} {e 1}
166 % lsort -index 1 {{a 5} { c 3} {b 4} {e 1} {d 2}}
167 {e 1} {d 2} { c 3} {b 4} {a 5}
168 Sorting a dictionary: │
170 % set d [dict create c d a b h i f g c e] │
172 c e a b h i f g │
173 % lsort -stride 2 $d │
174 a b c e f g h i │
175 Sorting using striding and multiple indices: │
177 % # Note the first index value is relative to the group │
179 % lsort -stride 3 -index {0 1} \ │
180 {{Bob Smith} 25 Audi {Jane Doe} 40 Ford} │
181 {{Jane Doe} 40 Ford {Bob Smith} 25 Audi} │
182 Stripping duplicate values using sorting:
184 % lsort -unique {a b c a b c a b c}
186 a b c
187 More complex sorting using a comparison function:
189 % proc compare {a b} {
191 set a0 [lindex $a 0]
192 set b0 [lindex $b 0]
193 if {$a0 < $b0} {
194 return -1
195 } elseif {$a0 > $b0} {
196 return 1
197 }
198 return [string compare [lindex $a 1] [lindex $b 1]]
199 }
200 % lsort -command compare \
201 {{3 apple} {0x2 carrot} {1 dingo} {2 banana}}
202 {1 dingo} {2 banana} {0x2 carrot} {3 apple}
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205 list(n), lappend(n), lindex(n), linsert(n), llength(n), lsearch(n),
206 lset(n), lrange(n), lreplace(n)
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209 element, list, order, sort
210Tcl 8.5 lsort(n)