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Some folks might think: “you still use RCS”?!? And we will say, hey, at least we switched from SCCS to RCS back in … I think it was around 1994 ... at least we are keeping up! :-) :-) :-) Logs say that SCCS version 18 became RCS version 19 on 1994 March 18. RCS served us well. But now it is time to move on. And so we are switching to git. Calc releases produce a lot of file changes. In the 125 releases of calc since 1996, when I started managing calc releases, there have been 15473 file mods!
133 lines
4.8 KiB
Plaintext
133 lines
4.8 KiB
Plaintext
NAME
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rsearch - reverse search for an element satisfying a specified condition
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SYNOPSIS
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rsearch(a, b [, [c] [, [d] ] ])
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TYPES
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a matrix, list, association, or file open for reading
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b string if a is a file, otherwise any
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c integer, defaults to zero, size(a) or the current file-position
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d integer, defaults to size(a) or current file-position
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return nonnegative integer or null
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DESCRIPTION
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Negative values of c and nonpositive values of d are treated as
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offsets from size(a), i.e. as if c were replaced by size(a) + c
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and d by size(a) + d. Any such adjustment is assumed to have been
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made.
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The nature of the search depends on whether the rsearch() is called
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with or without the fourth argument d.
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Four argument case:
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The search interval is as for search(a,b,c,d), i.e. the indices i
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to be examined are to satisfy c <= i < d and 0 <= i < size(a)
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for non-file a, and c <= i <= d - strlen(b), 0 <= i <= size(a) - strlen(b)
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if a is a file stream. The difference from search(a,b,c,d) is that
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the indices i, if any, are examined in decreasing order, so that
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if a match is found, the returned integer i is the largest in the
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search interval. The null value is returned if no match is found.
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The default value for d is size(a) for non-file cases, and the current
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file-position if a is a file. The default for c is zero except if a
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is a file and d is an integer.
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For non-file a, the search is for a[[i]] == b, except that if
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the function accept() as been defined, it is for i such that
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accept(a[[i]], b) tests as nonzero. Since the addresses (rather than
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values) of a[[i]] and b are passed to accept(), the values of one or
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both of a[[i]] and b may be changed during a call to rsearch().
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In the file-stream case, if strlen(b) = n, a match at file-position i
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corresponds to the n characters in the file starting at position i
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matching those of the string b. The null value is returned if no
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match is found. The final file position will correspond to the
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last character if a match is found, or the start (lowest) position
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of the search interval if no match is found, except that if no
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reading of characters is required (e.g. if start > end), the original
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file-position is not changed.
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Two- or Three-argument case:
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If a is not a file, the default value for c is size(a). If a is a
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file, rsearch(a,b) = rsearch(a, b, ftell(a)), and
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rsearch(a,b,) = rsearch(a, b, size(a)).
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If a is not a file, the search starts, if at all, at the largest
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non-negative index i for which i <= c and i < size(a), and continues
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until a match a[[i]] == b is found, or if accept() has been defined,
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accept(a[[i]], b) tests as nonzero; if no such i is found and returned,
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the null value is returned.
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If a is a file, the first, if any, file-position tested has the greatest
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nonnegative position i such that i <= c and i <= size(a) - strlen(b).
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The returned value is either the first i at which a match is found or
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the null value if no match with the string b is found. The final
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file-position will correspond to the last character of b, or the zero
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position, according as a match is found or not found.
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EXAMPLE
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; L = list(2,"three",4i)
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; rsearch(L,"three")
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1
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; rsearch(L,"threes")
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; rsearch(L, 4i, 4)
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; rsearch(L, 4i, 1)
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2
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; f = fopen("foo", "w+")
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; fputs(f, "This file has 28 characters.")
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; fflush(f)
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; rsearch(f, "ha")
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18
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; ftell(f)
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19
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; rsearch(f, "ha", 17)
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10
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; rsearch(f, "ha", 9)
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; ftell(f)
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0
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; rsearch(f, "ha")
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18
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; rsearch(f, "ha", 5, 500)
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18
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LIMITS
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none
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LINK LIBRARY
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none
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SEE ALSO
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append, delete, insert, islist, pop, push, remove, search,
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select, size,
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assoc, list, mat
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## Copyright (C) 1999-2006 Landon Curt Noll
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##
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## Calc is open software; you can redistribute it and/or modify it under
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## the terms of the version 2.1 of the GNU Lesser General Public License
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## as published by the Free Software Foundation.
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##
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## Calc is distributed in the hope that it will be useful, but WITHOUT
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## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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## or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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## Public License for more details.
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##
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## A copy of version 2.1 of the GNU Lesser General Public License is
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## distributed with calc under the filename COPYING-LGPL. You should have
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## received a copy with calc; if not, write to Free Software Foundation, Inc.
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## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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##
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## Under source code control: 1994/03/19 03:13:21
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## File existed as early as: 1994
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##
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## chongo <was here> /\oo/\ http://www.isthe.com/chongo/
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## Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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