search

Calc Software Package for Number Calc

NAME
    search - search for an element satisfying a specified condition

SYNOPSIS
    search(a, b [, [c] [, [d] ] ])

TYPES
    a		matrix, list, association or file
    b		string if a is a file, otherwise any
    c		integer, defaults to zero or current file-position
    d		integer, defaults to size(a) or current file-position

    return	nonnegative integer or null value

DESCRIPTION

    Negative values of c and nonpositive values for d are treated as
    offsets from size(a), i.e. as if c were replaced by size(a) + c,
    and d by size(a) + d.  Any such adjustment is assumed in the following
    description.


    For Non-file a:

    For a matrix, list, or association a,
    search(a, b, c, d) returns, if it exists, the least index i for which
    c <= i < d,	 0 <= i < size(a), and, if accept() has not been defined,
    a[[i]] == b, or if accept() has been defined, accept(a[[i]], b)
    tests as nonzero.  The null value is returned if there is no such i.

    For example, to search for the first a[[i]] > b an appropriate
    accept() function is given by:

		define accept(v,b) = (v > b);

    To restore the original behavior of search(), one may then use

		define accept(v, b) = (v == b).

    Since the addresses (rather than values) of a and b are passed,
    the values of v = x[[i]] and b may be changed during execution
    of search(a, b, c, d), e.g. if accept(v,b) has been defined by

		define accept(v,b) = (v > b ? v-- : b++);


    For a is a file-stream:

    c defaults to the current file-position if there are just two
    arguments (a,b) or if there are four arguments as in (a,b, ,d)
    where d is an integer.  Otherwise c defaults to zero.

    d defaults to the current file-position or size(a) according as
    the number of arguments (indicated by commas) is four or less
    than four.

    If a is a file, a string formed by n successive characters in a
    is considered to occur at the file position
    of the first character.  E.g. if a has the characters "123456",
    the string "345" is said to occur at position 2.

    The file is searched forwards from file-position pos = c for
    a match with b (not including the terminating '\0').
    Only characters with file-positions less than d are considered,
    so the effective interval for the first-character position pos
    for a matching string is limited by both c <= pos <= d - strlen(b)
    and 0 <= pos < size(a) - strlen(b).

    The function returns pos if a match is found, and the reading position
    for the stream after the search will then correspond to the position of
    the terminating '\0' for the string b.

    The null value is returned if no match is found.  If c, d, size(a)
    and strlen(b) are such that no match is possible, no reading of the
    file occurs and the current file-position is not changed.  In a case
    where characters are read, the final file-position will be
    min(d, size(a)) - strlen(b) + 1,
    i.e. the file will be at the first position where a match is impossible
    because the specified search region has insufficient remaining characters.

EXAMPLE
    ; L = list(2,"three",4i)
    ; search(L,"three")
	    1
    ; search(L,"threes")
    ; search(L, 4i, 4)
    ; search(L, 4i, 1)
	    2

    ; f = fopen("foo", "w+")
    ; fputs(f, "This file has 28 characters.")
    ; rewind(f)
    ; search(f, "ha")
	10
    ; ftell(f)
	12
    ; search(f, "ha")
	18
    ; search(f, "ha")
    ; search(f, "ha",)
	10
    ; search(f, "ha", 12)
	18
    ; search(f, "ha", -10)
	18
    ; search(f, "ha", ,)
	10
    ; search(f, "ha", 11, 19)
    ; ftell(f)
	18
    ; search(f, "ha", 11, 20)
	18
    ; search(f, "ha", 5, 500)
	10

LIMITS
    none

LINK LIBRARY
    none

SEE ALSO
     append, delete, insert, islist, pop, push, remove, rsearch,
     select, size,

     assoc, list, mat

## Copyright (C) 1999-2006  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.4 $
## @(#) $Id: search,v 29.4 2006/06/25 22:16:55 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/search,v $
##
## Under source code control:	1994/03/19 03:13:21
## File existed as early as:	1994
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/