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75 lines
1.5 KiB
75 lines
1.5 KiB
package main
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import (
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"math/rand"
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"strings"
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)
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func first(s, arg string) agg { return &sbinop{s, opfirst} }
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func last(s, arg string) agg { return &sbinop{s, oplast} }
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func prefix(s, arg string) agg { return &sbinop{s, opprefix} }
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func join(s, arg string) agg { return &sbinop{s, opjoin(arg)} }
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func smin(s, arg string) agg { return &sbinop{s, opsmin} }
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func smax(s, arg string) agg { return &sbinop{s, opsmax} }
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type sbinop struct {
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s string
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f func(a, b string) string
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}
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func (o *sbinop) String() string { return o.s }
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func (o *sbinop) merge(s string) { o.s = o.f(o.s, s) }
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func opfirst(a, b string) string { return a }
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func oplast(a, b string) string { return b }
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func opprefix(a, b string) string {
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for i := range a {
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if i >= len(b) || a[i] != b[i] {
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return a[:i]
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}
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}
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return a
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}
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func opjoin(sep string) func(a, b string) string {
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return func(a, b string) string {
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return a + sep + b // TODO(kr): too slow? maybe strings.Join?
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}
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}
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func opsmin(a, b string) string {
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if strings.Compare(a, b) <= 0 {
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return a
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}
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return b
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}
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func opsmax(a, b string) string {
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if strings.Compare(a, b) >= 0 {
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return a
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}
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return b
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}
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type sampler struct {
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n int
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s string
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}
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func sample(s, arg string) agg { return &sampler{1, s} }
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func (p *sampler) String() string { return p.s }
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func (p *sampler) merge(s string) {
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p.n++
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if rand.Intn(p.n) == 0 {
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p.s = s
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}
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}
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type constant string
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func constf(init, arg string) agg { return constant(arg) }
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func (c constant) String() string { return string(c) }
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func (c constant) merge(string) {}
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