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diff --git a/share/doc/usd/22.trofftut/tt08 b/share/doc/usd/22.trofftut/tt08 new file mode 100644 index 000000000000..f6b4c7ee34c2 --- /dev/null +++ b/share/doc/usd/22.trofftut/tt08 @@ -0,0 +1,196 @@ +.\" This module is believed to contain source code proprietary to AT&T. +.\" Use and redistribution is subject to the Berkeley Software License +.\" Agreement and your Software Agreement with AT&T (Western Electric). +.\" Copyright (C) Caldera International Inc. 2001-2002. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions are +.\" met: +.\" +.\" Redistributions of source code and documentation must retain the above +.\" copyright notice, this list of conditions and the following +.\" disclaimer. +.\" +.\" Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" +.\" This product includes software developed or owned by Caldera +.\" International, Inc. Neither the name of Caldera International, Inc. +.\" nor the names of other contributors may be used to endorse or promote +.\" products derived from this software without specific prior written +.\" permission. +.\" +.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA +.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE +.\" DISCLAIMED. IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE +.\" FOR ANY DIRECT, INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR +.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR +.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE +.\" OR OTHERWISE) RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN +.\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\" +.NH +Introduction to Macros +.PP +Before we can go much further in +.UL troff , +we need to learn a bit about the +macro +facility. +In its simplest form, a macro is just a shorthand notation +quite similar to a string. +Suppose we want every paragraph to start +in exactly the same way _ +with a space and a temporary indent of two ems: +.P1 +^sp +^ti +2m +.P2 +Then to save typing, we would like to collapse these into +one shorthand line, +a +.UL troff +`command' like +.P1 +^PP +.P2 +that would be treated by +.UL troff +exactly as +.P1 +^sp +^ti +2m +.P2 +.BD .PP +is called a +.ul +macro. +The way we tell +.UL troff +what +.BD .PP +means is to +.ul +define +it with the +.BD .de +command: +.P1 +^de PP +^sp +^ti +2m +^^ +.P2 +The first line names the macro +(we used +.BD .PP ' ` +for `paragraph', +and upper case so it wouldn't conflict with +any name that +.UL troff +might +already know about). +The last line +.BD .. +marks the end of the definition. +In between is the text, +which is simply inserted whenever +.UL troff +sees the `command' +or macro call +.P1 +^PP +.P2 +A macro +can contain any mixture of text and formatting commands. +.PP +The definition of +.BD .PP +has to precede its first use; +undefined macros are simply ignored. +Names are restricted to one or two characters. +.PP +Using macros for commonly occurring sequences of commands +is critically important. +Not only does it save typing, +but it makes later changes much easier. +Suppose we decide that the paragraph indent is too small, +the vertical space is much too big, +and roman font should be forced. +Instead of changing the whole document, +we need only change the definition of +.BD .PP +to +something like +.P1 +^de PP \e" paragraph macro +^sp 2p +^ti +3m +^ft R +^^ +.P2 +and the change takes +effect everywhere we used +.BD .PP . +.PP +.BD \e" +is a +.UL troff +command that causes the rest of the line to be ignored. +We use it here to add comments to the macro +definition +(a wise idea once definitions get complicated). +.PP +As another example of macros, +consider these two which start and end a block of offset, +unfilled text, like most of the examples in this paper: +.P1 +^de BS \e" start indented block +^sp +^nf +^in +0.3i +^^ +^de BE \e" end indented block +^sp +^fi +^in \(mi0.3i +^^ +.P2 +Now we can surround text like +.P1 +Copy to +John Doe +Richard Roberts +Stanley Smith +.P2 +by the commands +.BD .BS +and +.BD .BE , +and it will come out as it did above. +Notice that we indented by +.BD .in\ +0.3i +instead of +.BD .in\ 0.3i . +This way we can nest our uses of +.BD .BS +and +.BD BE +to get blocks within blocks. +.PP +If later on we decide that the indent +should be 0.5i, then it is only necessary to +change the definitions of +.BD .BS +and +.BD .BE , +not the whole paper. |