File: funcombine.n

package info (click to toggle)
funtools 1.4.4+dfsg2-1
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-kfreebsd
  • size: 16,168 kB
  • ctags: 10,760
  • sloc: ansic: 87,238; sh: 9,727; lex: 4,595; asm: 3,281; ada: 1,681; makefile: 1,458; pascal: 1,089; cpp: 1,001; cs: 879; perl: 161; yacc: 64; sed: 32; csh: 10; tcl: 9
file content (248 lines) | stat: -rw-r--r-- 6,899 bytes parent folder | download
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
242
243
244
245
246
247
248
.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  | will give a
.\" real vertical bar.  \*(C+ will give a nicer C++.  Capital omega is used to
.\" do unbreakable dashes and therefore won't be available.  \*(C` and \*(C'
.\" expand to `' in nroff, nothing in troff, for use with C<>.
.tr \(*W-|\(bv\*(Tr
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.if \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.\"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "funcombine 7"
.TH funcombine 7 "January 2, 2008" "version 1.4.2" "SAORD Documentation"
.SH "NAME"
\&\fBFunCombine \- Combining Region and Table Filters\fR
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
This document discusses the conventions for combining region and table
filters, especially with regards to the comma operator.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBComma Conventions\fR
.PP
Filter specifications consist of a series of boolean expressions,
separated by commas. These expressions can be table filters,
spatial region filters, or combinations thereof. Unfortunately,
common usage requires that the comma operator must act differently
in different situations. Therefore, while its use is intuitive in
most cases, commas can be a source of confusion.
.PP
According to long-standing usage in \s-1IRAF\s0, when a comma separates two
table filters, it takes on the meaning of a boolean \fBand\fR. Thus:
.PP
.Vb 1
\&  foo.fits[pha==1,pi==2]
.Ve
.PP
is equivalent to:
.PP
.Vb 1
\&  foo.fits[pha==1 && pi==2]
.Ve
.PP
When a comma separates two spatial region filters, however, it has
traditionally taken on the meaning of a boolean \fBor\fR. Thus:
.PP
.Vb 1
\&  foo.fits[circle(10,10,3),ellipse(20,20,8,5)]
.Ve
.PP
is equivalent to:
.PP
.Vb 1
\&  foo.fits[circle(10,10,3) || ellipse(20,20,8,5)]
.Ve
.PP
(except that in the former case, each region is given a unique id
in programs such as funcnts).
.PP
Region and table filters can be combined:
.PP
.Vb 1
\&  foo.fits[circle(10,10,3),pi=1:5]
.Ve
.PP
or even:
.PP
.Vb 1
\&  foo.fits[pha==1&&circle(10,10,3),pi==2&&ellipse(20,20,8,5)]
.Ve
.PP
In these cases, it is not obvious whether the command should utilize an
\&\fBor\fR or \fBand\fR operator. We therefore arbitrarily chose to
implement the following rule:
.IP "\(bu" 4
if both expressions contain a region, the operator used is \fBor\fR.
.IP "\(bu" 4
if one (or both) expression(s) does not contain a region, the operator
used is \fBand\fR.
.PP
This rule handles the cases of pure regions and pure column filters properly.
It unambiguously assigns the boolean \fBand\fR to all mixed cases. Thus:
.PP
.Vb 1
\&  foo.fits[circle(10,10,3),pi=1:5]
.Ve
.PP
and
.PP
.Vb 1
\&  foo.fits[pi=1:5,circle(10,10,3)]
.Ve
.PP
both are equivalent to:
.PP
.Vb 1
\&  foo.fits[circle(10,10,3) && pi=1:5]
.Ve
.PP
[\s-1NB:\s0 This arbitrary rule \fBreplaces the previous arbitrary rule\fR
(pre\-funtools 1.2.3) which stated:
.IP "\(bu" 4
if the 2nd expression contains a region, the operator used is \fBor\fR.
.IP "\(bu" 4
if the 2nd expression does not contain a region, the operator
used is \fBand\fR.
.PP
In that scenario, the \fBor\fR operator was implied by:
.PP
.Vb 1
\&  pha==4,circle 5 5 1
.Ve
.PP
while the \fBand\fR operator was implied by
.PP
.Vb 1
\&  circle 5 5 1,pha==4
.Ve
.PP
Experience showed that this non-commutative treatment of the comma
operator was confusing and led to unexpected results.]
.PP
The comma rule must be considered provisional: comments and complaints
are welcome to help clarify the matter. Better still, we recommend
that the comma operator be avoided in such cases in favor of an
explicit boolean operator.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
See funtools(n) for a list of Funtools help pages