List comprehensions: Difference between revisions
Added Go
(Removed {{omit from|Go}} template as this task can be completed by building something similar.) |
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# [ 13, 84, 85 ], [ 16, 63, 65 ], [ 20, 21, 29 ], [ 28, 45, 53 ], [ 33, 56, 65 ], [ 36, 77, 85 ], [ 39, 80, 89 ],
# [ 48, 55, 73 ], [ 65, 72, 97 ] ]</lang>
=={{header|Go}}==
Go doesn't have special syntax for list comprehensions but we can build a function which behaves similarly.
<lang go>package main
import "fmt"
type (
seq []int
sofs []seq
)
func newSeq(start, end int) seq {
if end < start {
end = start
}
s := make(seq, end-start+1)
for i := 0; i < len(s); i++ {
s[i] = start + i
}
return s
}
func newSofs() sofs {
return sofs{seq{}}
}
func (s sofs) listComp(in seq, expr func(sofs, seq) sofs, pred func(seq) bool) sofs {
var s2 sofs
for _, t := range expr(s, in) {
if pred(t) {
s2 = append(s2, t)
}
}
return s2
}
func (s sofs) build(t seq) sofs {
var u sofs
for _, ss := range s {
for _, tt := range t {
uu := make(seq, len(ss))
copy(uu, ss)
uu = append(uu, tt)
u = append(u, uu)
}
}
return u
}
func main() {
pt := newSofs()
in := newSeq(1, 20)
expr := func(s sofs, t seq) sofs {
return s.build(t).build(t).build(t)
}
pred := func(t seq) bool {
if len(t) != 3 {
return false
}
return t[0]*t[0]+t[1]*t[1] == t[2]*t[2] && t[0] < t[1] && t[1] < t[2]
}
pt = pt.listComp(in, expr, pred)
fmt.Println(pt)
}</lang>
{{out}}
<pre>
[[3 4 5] [5 12 13] [6 8 10] [8 15 17] [9 12 15] [12 16 20]]
</pre>
=={{header|Haskell}}==
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