2016-02-16 19:17:33 -05:00
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.Dd 2016-02-16
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.Dt TSORT 1
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.Os sbase
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.Sh NAME
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.Nm tsort
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.Nd topological sort
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.Sh SYNOPSIS
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.Nm
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.Op Ar file
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.Sh DESCRIPTION
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.Nm
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2020-03-01 17:37:31 -05:00
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topologically sorts a graph.
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The graph is read either from
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.Ar file
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2020-03-01 17:37:31 -05:00
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or from standard input.
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The result is not optimized for any particular usage.
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Loops are detected and reported to standard error, but does not stop the
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sort.
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.Pp
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The input is a list of edges (vertex pairs), where
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the edge is directed from the first vertex to the
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second vertex.
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.Sh OPTIONS
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None.
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.Sh EXIT STATUS
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.Bl -tag -width Ds
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.It 0
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The graph as successfully sorted.
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.It 1
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The graph as successfully sorted, but contained loops.
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.It > 1
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An error occurred.
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.El
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.Sh EXAMPLES
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2016-02-25 14:44:15 -05:00
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.Bd -literal -offset left
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The input
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a a
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a b
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a c
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a c
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a d
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b c
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c b
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e f
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or equivalently
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a a a b a c a c a d
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b c c b e f
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represents the graph
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┌─┐
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↓ │
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┏━━━┓
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┌──────┃ a ┃──────┐
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│ ┗━━━┛ │
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│ │ │ │
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↓ ↓ ↓ ↓
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┏━━━┓───→┏━━━┓ ┏━━━┓
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┃ b ┃ ┃ c ┃ ┃ d ┃
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┗━━━┛←───┗━━━┛ ┗━━━┛
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┏━━━┓ ┏━━━┓
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┃ e ┃───→┃ f ┃
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┗━━━┛ ┗━━━┛
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.Ed
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.Sh STANDARDS
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The
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.Nm
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utility is compliant with the
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.St -p1003.1-2013
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specification.
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