This file is indexed.

/usr/share/doc/swi-prolog-doc/Manual/option.html is in swi-prolog-doc 5.6.59-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<HTML>
<HEAD>
<TITLE>SWI-Prolog 5.6.59 Reference Manual: Section A.14</TITLE><LINK REL=home HREF="index.html">
<LINK REL=contents HREF="Contents.html">
<LINK REL=index HREF="DocIndex.html">
<LINK REL=previous HREF="www_browser.html">
<LINK REL=next HREF="ordsets.html">
<STYLE type="text/css">
/* Style sheet for SWI-Prolog latex2html
*/

dd.defbody
{ margin-bottom: 1em;
}

dt.pubdef
{ background-color: #c5e1ff;
}

pre.code
{ margin-left: 1.5em;
margin-right: 1.5em;
border: 1px dotted;
padding-top: 5px;
padding-left: 5px;
padding-bottom: 5px;
background-color: #f8f8f8;
}

div.navigate
{ text-align: center;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
}

div.title
{ text-align: center;
padding-bottom: 1em;
font-size: 200%;
font-weight: bold;
}

div.author
{ text-align: center;
font-style: italic;
}

div.abstract
{ margin-top: 2em;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
margin-left: 10%; margin-right:10%;
}

div.abstract-title
{ text-align: center;
padding: 5px;
font-size: 120%;
font-weight: bold;
}

div.toc-h1
{ font-size: 200%;
font-weight: bold;
}

div.toc-h2
{ font-size: 120%;
font-weight: bold;
margin-left: 2em;
}

div.toc-h3
{ font-size: 100%;
font-weight: bold;
margin-left: 4em;
}

div.toc-h4
{ font-size: 100%;
margin-left: 6em;
}

span.sec-nr
{ 
}

span.sec-title
{ 
}

span.pred-ext
{ font-weight: bold;
}

span.pred-tag
{ float: right;
font-size: 80%;
font-style: italic;
color: #202020;
}

/* Footnotes */

sup.fn { color: blue; text-decoration: underline; }
span.fn-text { display: none; }
sup.fn span {display: none;}
sup:hover span 
{ display: block !important;
position: absolute; top: auto; left: auto; width: 80%;
color: #000; background: white;
border: 2px solid;
padding: 5px; margin: 10px; z-index: 100;
font-size: smaller;
}
</STYLE>
</HEAD>
<BODY BGCOLOR="white">
<DIV class="navigate"><A class="nav" href="index.html"><IMG SRC="home.gif" BORDER=0 ALT="Home"></A>
<A class="nav" href="Contents.html"><IMG SRC="index.gif" BORDER=0 ALT="Contents"></A>
<A class="nav" href="DocIndex.html"><IMG SRC="yellow_pages.gif" BORDER=0 ALT="Index"></A>
<A class="nav" href="www_browser.html"><IMG SRC="prev.gif" BORDER=0 ALT="Previous"></A>
<A class="nav" href="ordsets.html"><IMG SRC="next.gif" BORDER=0 ALT="Next"></A>
</DIV>

<H2><A NAME="sec:A.14"><SPAN class="sec-nr">A.14</SPAN> <SPAN class="sec-title">option.pl 
-- Option list processing</SPAN></A></H2>

<P><A NAME="sec:option"></A>

<DL>
<DT><B>See also</B><DD> library(record)<DT><B>To be done</B><DD>- We 
should consider putting many options in an assoc or record with 
appropriate preprocessing to achieve better performance. <BR>
- We should provide some standard to to automatic type-checking on 
option lists.
</DL>

<P>The library(option) provides some utilities for processing option 
lists. Option lists are commonly used as an alternative for many 
arguments. Examples built-in predicates are <A class="pred" href="IO.html#open/4">open/4</A> 
and <A class="pred" href="termrw.html#write_term/3">write_term/3</A>. 
Naming the arguments results in more readable code and the list nature 
makes it easy to extend the list of options accepted by a predicate. 
Option lists come in two styles, both of which are handled by this 
library.

<DL>
<DT><B>Name(Value)</B></DT>
<DD>
This is the preferred style.
</DD>
<DT><B>Name = Value</B></DT>
<DD>
This is often used, but deprecated.
</DD>
</DL>

<P>Processing options inside time critical code (loops) can cause 
serious overhead. One possibility is to define a record using 
library(record) and initialise this using make_<VAR>&lt;</VAR>record<A class="pred" href="arith.html#>/2">&gt;/2</A>. 
In addition to providing good performance, this also provides 
type-checking and central declaration of defaults.

<PRE class="code">
:- record atts(width:integer=100, shape:oneof([box,circle])=box).

process(Data, Options) :-
        make_atts(Options, Attributes),
        action(Data, Attributes).

action(Data, Attributes) :-
        atts_shape(Attributes, Shape),
        ...
</PRE>

<DL>
<DT class="pubdef"><A NAME="option/3"><STRONG>option</STRONG>(<VAR>?Option, 
+OptionList, +Default</VAR>)</A></DT>
<DD class="defbody">
Get an option from a <VAR>OptionList</VAR>. <VAR>OptionList</VAR> can 
use the Name=Value as well as the Name(Value) convention.
<TABLE class="paramlist">
<TR VALIGN=top><TD><VAR>Option</VAR> </TD><TD>Term of the form 
Name(?Value). </TD></TR>
</TABLE>

</DD>
<DT class="pubdef"><A NAME="option/2"><STRONG>option</STRONG>(<VAR>?Option, 
+OptionList</VAR>)</A></DT>
<DD class="defbody">
Get an option from a <VAR>OptionList</VAR>. <VAR>OptionList</VAR> can 
use the Name=Value as well as the Name(Value) convention. Fails silently 
if the option does not appear in <VAR>OptionList</VAR>.
<TABLE class="paramlist">
<TR VALIGN=top><TD><VAR>Option</VAR> </TD><TD>Term of the form 
Name(?Value). </TD></TR>
</TABLE>

</DD>
<DT class="pubdef"><span class="pred-tag">[semidet]</span><A NAME="select_option/3"><STRONG>select_option</STRONG>(<VAR>?Option, 
+Options, -RestOptions</VAR>)</A></DT>
<DD class="defbody">
Get and remove option from an option list. As <A class="pred" href="option.html#option/2">option/2</A>, 
removing the matching option from <VAR>Options</VAR> and unifying the 
remaining options with <VAR>RestOptions</VAR>.</DD>
<DT class="pubdef"><span class="pred-tag">[det]</span><A NAME="select_option/4"><STRONG>select_option</STRONG>(<VAR>?Option, 
+Options, -RestOptions, +Default</VAR>)</A></DT>
<DD class="defbody">
Get and remove option with default value. As <A class="pred" href="option.html#select_option/3">select_option/3</A>, 
but if <VAR>Option</VAR> is not in <VAR>Options</VAR>, its value is 
unified with
<VAR>Default</VAR> and <VAR>RestOptions</VAR> with <VAR>Options</VAR>.</DD>
<DT class="pubdef"><span class="pred-tag">[det]</span><A NAME="merge_options/3"><STRONG>merge_options</STRONG>(<VAR>+New, 
+Old, -Merged</VAR>)</A></DT>
<DD class="defbody">
Merge two option lists. <VAR>Merged</VAR> is a sorted list of options 
using the canonical format Name(Value) holding all options from <VAR>New</VAR> 
and <VAR>Old</VAR>, after removing conflicting options from <VAR>Old</VAR>.</DD>
<DT class="pubdef"><span class="pred-tag">[det]</span><A NAME="meta_options/3"><STRONG>meta_options</STRONG>(<VAR>+IsMeta, 
:Options0, -Options</VAR>)</A></DT>
<DD class="defbody">
Perform meta-expansion on options that are module-sensitive. Whether an 
option name is module sensitive is determined by calling call(<VAR>IsMeta</VAR>, 
Name). Here is an example:

<PRE class="code">
        meta_options(is_meta, OptionsIn, Options),
        ...

is_meta(callback).
</PRE>

<P></DD>
</DL>

<P></BODY></HTML>