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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16 This command sorts the elements of list, returning a new list in sorted
17 order. The implementation of the lsort command uses the merge-sort
18 algorithm which is a stable sort that has O(n log n) performance char‐
19 acteristics.
20 By default ASCII sorting is used with the result returned in increasing
22 order. However, any of the following options may be specified before
23 list to control the sorting process (unique abbreviations are
24 accepted):
25 -ascii Use string comparison with Unicode code-point col‐
27 lation order (the name is for backward-compatibil‐
28 ity reasons.) This is the default.
29 -dictionary Use dictionary-style comparison. This is the same
31 as -ascii except (a) case is ignored except as a
32 tie-breaker and (b) if two strings contain embedded
33 numbers, the numbers compare as integers, not char‐
34 acters. For example, in -dictionary mode, bigBoy
35 sorts between bigbang and bigboy, and x10y sorts
36 between x9y and x11y.
37 -integer Convert list elements to integers and use integer
39 comparison.
40 -real Convert list elements to floating-point values and
42 use floating comparison.
43 -command command Use command as a comparison command. To compare
45 two elements, evaluate a Tcl script consisting of
46 command with the two elements appended as addi‐
47 tional arguments. The script should return an
48 integer less than, equal to, or greater than zero
49 if the first element is to be considered less than,
50 equal to, or greater than the second, respectively.
51 -increasing Sort the list in increasing order (“smallest”items
53 first). This is the default.
54 -decreasing Sort the list in decreasing order (“largest”items
56 first).
57 -indices Return a list of indices into list in sorted order │
59 instead of the values themselves.
60 -index indexList If this option is specified, each of the elements
62 of list must itself be a proper Tcl sublist.
63 Instead of sorting based on whole sublists, lsort
64 will extract the indexList'th element from each
65 sublist (as if the overall element and the │
66 indexList were passed to lindex) and sort based on │
67 the given element. For example,
68 lsort -integer -index 1 \
69 {{First 24} {Second 18} {Third 30}}
70 returns {Second 18} {First 24} {Third 30}, and
71 lsort -index end-1 \
72 {{a 1 e i} {b 2 3 f g} {c 4 5 6 d h}}
73 returns {c 4 5 6 d h} {a 1 e i} {b 2 3 f g}, and │
74 lsort -index {0 1} { │
75 {{b i g} 12345} │
76 {{d e m o} 34512} │
77 {{c o d e} 54321} │
78 } │
79 returns {{d e m o} 34512} {{b i g} 12345} {{c o d │
80 e} 54321} (because e sorts before i which sorts │
81 before o.) This option is much more efficient than
82 using -command to achieve the same effect.
83 -nocase │
85 Causes comparisons to be handled in a case-insensi‐ │
86 tive manner. Has no effect if combined with the │
87 -dictionary, -integer, or -real options.
88 -unique If this option is specified, then only the last set
90 of duplicate elements found in the list will be
91 retained. Note that duplicates are determined rel‐
92 ative to the comparison used in the sort. Thus if
93 -index 0 is used, {1 a} and {1 b} would be consid‐
94 ered duplicates and only the second element, {1 b},
95 would be retained.
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98 The options to lsort only control what sort of comparison is used, and
99 do not necessarily constrain what the values themselves actually are.
100 This distinction is only noticeable when the list to be sorted has
101 fewer than two elements.
102 The lsort command is reentrant, meaning it is safe to use as part of
104 the implementation of a command used in the -command option.
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107 Sorting a list using ASCII sorting:
108 % lsort {a10 B2 b1 a1 a2}
109 B2 a1 a10 a2 b1
110 Sorting a list using Dictionary sorting:
112 % lsort -dictionary {a10 B2 b1 a1 a2}
113 a1 a2 a10 b1 B2
114 Sorting lists of integers:
116 % lsort -integer {5 3 1 2 11 4}
117 1 2 3 4 5 11
118 % lsort -integer {1 2 0x5 7 0 4 -1}
119 -1 0 1 2 4 0x5 7
120 Sorting lists of floating-point numbers:
122 % lsort -real {5 3 1 2 11 4}
123 1 2 3 4 5 11
124 % lsort -real {.5 0.07e1 0.4 6e-1}
125 0.4 .5 6e-1 0.07e1
126 Sorting using indices:
128 % # Note the space character before the c
129 % lsort {{a 5} { c 3} {b 4} {e 1} {d 2}}
130 { c 3} {a 5} {b 4} {d 2} {e 1}
131 % lsort -index 0 {{a 5} { c 3} {b 4} {e 1} {d 2}}
132 {a 5} {b 4} { c 3} {d 2} {e 1}
133 % lsort -index 1 {{a 5} { c 3} {b 4} {e 1} {d 2}}
134 {e 1} {d 2} { c 3} {b 4} {a 5}
135 Stripping duplicate values using sorting:
137 % lsort -unique {a b c a b c a b c}
138 a b c
139 More complex sorting using a comparison function:
141 % proc compare {a b} {
142 set a0 [lindex $a 0]
143 set b0 [lindex $b 0]
144 if {$a0 < $b0} {
145 return -1
146 } elseif {$a0 > $b0} {
147 return 1
148 }
149 return [string compare [lindex $a 1] [lindex $b 1]]
150 }
151 % lsort -command compare \
152 {{3 apple} {0x2 carrot} {1 dingo} {2 banana}}
153 {1 dingo} {2 banana} {0x2 carrot} {3 apple}
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157 list(n), lappend(n), lindex(n), linsert(n), llength(n), lsearch(n),
158 lset(n), lrange(n), lreplace(n)
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162 element, list, order, sort
163Tcl 8.5 lsort(n)