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diff --git a/funtools/man/man7/funcombine.7 b/funtools/man/man7/funcombine.7 new file mode 100644 index 0000000..b2e5dc4 --- /dev/null +++ b/funtools/man/man7/funcombine.7 @@ -0,0 +1,248 @@ +.\" 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. 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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(7) for a list of Funtools help pages |