94 lines
2.0 KiB
Go
94 lines
2.0 KiB
Go
package main
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import (
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"fmt"
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"sort"
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)
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type cell string
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type row []cell
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type table struct {
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rows []row
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column int
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less func(cell, cell) bool
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}
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func (c cell) String() string {
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return fmt.Sprintf("%q", string(c))
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}
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func (t table) printRows(heading string) {
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fmt.Println("--", heading)
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for _, row := range t.rows {
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fmt.Println(row)
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}
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fmt.Println()
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}
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// sort.Interface
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func (t table) Len() int { return len(t.rows) }
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func (t table) Swap(i, j int) { t.rows[i], t.rows[j] = t.rows[j], t.rows[i] }
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func (t table) Less(i, j int) bool {
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return t.less(t.rows[i][t.column], t.rows[j][t.column])
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}
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// struct implements named parameter-like capability
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type spec struct {
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ordering func(cell, cell) bool
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column int
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reverse bool
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}
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func (t *table) sort(s spec) {
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// set up column and comparison function for sort
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t.column = s.column
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switch {
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case s.ordering != nil:
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t.less = s.ordering
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case s.reverse:
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t.less = func(a, b cell) bool { return a > b }
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default:
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t.less = func(a, b cell) bool { return a < b }
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}
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// sort
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sort.Sort(t)
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// reverse if necessary
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if s.ordering == nil || !s.reverse {
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return
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}
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last := len(t.rows) - 1
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for i := last / 2; i >= 0; i-- {
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t.rows[i], t.rows[last-i] = t.rows[last-i], t.rows[i]
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}
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}
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func main() {
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t := table{rows: []row{
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{"pail", "food"},
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{"pillbox", "nurse maids"},
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{"suitcase", "airedales"},
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{"bathtub", "chocolate"},
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{"schooner", "ice cream sodas"},
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}}
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t.printRows("song")
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// no "parameters"
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t.sort(spec{})
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t.printRows("sorted on first column")
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// "named parameter" reverse.
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t.sort(spec{reverse: true})
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t.printRows("reverse sorted on first column")
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// "named parameters" column and ordering
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t.sort(spec{
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column: 1,
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ordering: func(a, b cell) bool { return len(a) > len(b) },
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})
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t.printRows("sorted by descending string length on second column")
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}
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