'\" '\" Generated from file 'expander\&.man' by tcllib/doctools with format 'nroff' '\" Copyright (c) William H\&. Duquette, http://www\&.wjduquette\&.com/expand '\" .TH "textutil::expander" 3tcl 1\&.3\&.1 tcllib "Text and string utilities, macro processing" .\" The -*- nroff -*- definitions below are for supplemental macros used .\" in Tcl/Tk manual entries. .\" .\" .AP type name in/out ?indent? .\" Start paragraph describing an argument to a library procedure. .\" type is type of argument (int, etc.), in/out is either "in", "out", .\" or "in/out" to describe whether procedure reads or modifies arg, .\" and indent is equivalent to second arg of .IP (shouldn't ever be .\" needed; use .AS below instead) .\" .\" .AS ?type? ?name? .\" Give maximum sizes of arguments for setting tab stops. Type and .\" name are examples of largest possible arguments that will be passed .\" to .AP later. If args are omitted, default tab stops are used. .\" .\" .BS .\" Start box enclosure. From here until next .BE, everything will be .\" enclosed in one large box. .\" .\" .BE .\" End of box enclosure. .\" .\" .CS .\" Begin code excerpt. .\" .\" .CE .\" End code excerpt. .\" .\" .VS ?version? ?br? .\" Begin vertical sidebar, for use in marking newly-changed parts .\" of man pages. The first argument is ignored and used for recording .\" the version when the .VS was added, so that the sidebars can be .\" found and removed when they reach a certain age. If another argument .\" is present, then a line break is forced before starting the sidebar. .\" .\" .VE .\" End of vertical sidebar. .\" .\" .DS .\" Begin an indented unfilled display. .\" .\" .DE .\" End of indented unfilled display. .\" .\" .SO ?manpage? .\" Start of list of standard options for a Tk widget. The manpage .\" argument defines where to look up the standard options; if .\" omitted, defaults to "options". The options follow on successive .\" lines, in three columns separated by tabs. .\" .\" .SE .\" End of list of standard options for a Tk widget. .\" .\" .OP cmdName dbName dbClass .\" Start of description of a specific option. cmdName gives the .\" option's name as specified in the class command, dbName gives .\" the option's name in the option database, and dbClass gives .\" the option's class in the option database. .\" .\" .UL arg1 arg2 .\" Print arg1 underlined, then print arg2 normally. .\" .\" .QW arg1 ?arg2? .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation). .\" .\" .PQ arg1 ?arg2? .\" Print an open parenthesis, arg1 in quotes, then arg2 normally .\" (for trailing punctuation) and then a closing parenthesis. .\" .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b .\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ta \\n()Au \\n()Bu .ie !"\\$3"" \{\ \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. .\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out .\" # BS - start boxed text .\" # ^y = starting y location .\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. .\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. .\" # VS - start vertical sidebar .\" # ^Y = starting y location .\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$2"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. .\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. .\" # Special macro to handle page bottom: finish off current .\" # box/sidebar if in box/sidebar mode, then invoked standard .\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. .\" # DS - begin display .de DS .RS .nf .sp .. .\" # DE - end display .de DE .fi .RE .sp .. .\" # SO - start of list of standard options .de SO 'ie '\\$1'' .ds So \\fBoptions\\fR 'el .ds So \\fB\\$1\\fR .SH "STANDARD OPTIONS" .LP .nf .ta 5.5c 11c .ft B .. .\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\*(So manual entry for details on the standard options. .. .\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. .\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. .\" # CE - end code excerpt .de CE .fi .RE .. .\" # UL - underline word .de UL \\$1\l'|0\(ul'\\$2 .. .\" # QW - apply quotation marks to word .de QW .ie '\\*(lq'"' ``\\$1''\\$2 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\$2 .. .\" # PQ - apply parens and quotation marks to word .de PQ .ie '\\*(lq'"' (``\\$1''\\$2)\\$3 .\"" fix emacs highlighting .el (\\*(lq\\$1\\*(rq\\$2)\\$3 .. .\" # QR - quoted range .de QR .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3 .. .\" # MT - "empty" string .de MT .QW "" .. .BS .SH NAME textutil::expander \- Procedures to process templates and expand text\&. .SH SYNOPSIS package require \fBTcl 8\&.2\fR .sp package require \fBtextutil::expander ?1\&.3\&.1?\fR .sp \fB::textutil::expander\fR \fIexpanderName\fR .sp \fIexpanderName\fR \fBcappend\fR \fItext\fR .sp \fIexpanderName\fR \fBcget\fR \fIvarname\fR .sp \fIexpanderName\fR \fBcis\fR \fIcname\fR .sp \fIexpanderName\fR \fBcname\fR .sp \fIexpanderName\fR \fBcpop\fR \fIcname\fR .sp \fIexpanderName\fR \fBctopandclear\fR .sp \fIexpanderName\fR \fBcpush\fR \fIcname\fR .sp \fIexpanderName\fR \fBcset\fR \fIvarname\fR \fIvalue\fR .sp \fIexpanderName\fR \fBcvar\fR \fIvarname\fR .sp \fIexpanderName\fR \fBerrmode\fR \fInewErrmode\fR .sp \fIexpanderName\fR \fBevalcmd\fR ?\fInewEvalCmd\fR? .sp \fIexpanderName\fR \fBexpand\fR \fIstring\fR ?\fIbrackets\fR? .sp \fIexpanderName\fR \fBlb\fR ?\fInewbracket\fR? .sp \fIexpanderName\fR \fBrb\fR ?\fInewbracket\fR? .sp \fIexpanderName\fR \fBreset\fR .sp \fIexpanderName\fR \fBsetbrackets\fR \fIlbrack rbrack\fR .sp \fIexpanderName\fR \fBtextcmd\fR ?\fInewTextCmd\fR? .sp \fIexpanderName\fR \fBwhere\fR .sp .BE .SH DESCRIPTION .PP The Tcl \fBsubst\fR command is often used to support a kind of template processing\&. Given a string with embedded variables or function calls, \fBsubst\fR will interpolate the variable and function values, returning the new string: .PP .CS % set greeting "Howdy" Howdy % proc place {} {return "World"} % subst {$greeting, [place]!} Howdy, World! % .CE .PP By defining a suitable set of Tcl commands, \fBsubst\fR can be used to implement a markup language similar to HTML\&. .PP The \fBsubst\fR command is efficient, but it has three drawbacks for this kind of template processing: .IP \(bu There's no way to identify and process the plain text between two embedded Tcl commands; that makes it difficult to handle plain text in a context-sensitive way\&. .IP \(bu Embedded commands are necessarily bracketed by \fB[\fR and \fB]\fR; it's convenient to be able to choose different brackets in special cases\&. Someone producing web pages that include a large quantity of Tcl code examples might easily prefer to use \fB<<\fR and \fB>>\fR as the embedded code delimiters instead\&. .IP \(bu There's no easy way to handle incremental input, as one might wish to do when reading data from a socket\&. .PP .PP At present, expander solves the first two problems; eventually it will solve the third problem as well\&. .PP The following section describes the command API to the expander; this is followed by the tutorial sections, see \fBTUTORIAL\fR\&. .SH "EXPANDER API" .PP The \fBtextutil::expander\fR package provides only one command, described below\&. The rest of the section is taken by a description of the methods for the expander objects created by this command\&. .TP \fB::textutil::expander\fR \fIexpanderName\fR The command creates a new expander object with an associated Tcl command whose name is \fIexpanderName\fR\&. This command may be used to invoke various operations on the graph\&. If the \fIexpanderName\fR is not fully qualified it is interpreted as relative to the current namespace\&. The command has the following general form: .CS \fIexpanderName\fR option ?\fIarg arg \&.\&.\&.\fR? .CE .IP \fIOption\fR and the \fIarg\fRs determine the exact behavior of the command\&. .PP .PP The following commands are possible for expander objects: .TP \fIexpanderName\fR \fBcappend\fR \fItext\fR Appends a string to the output in the current context\&. This command should rarely be used by macros or application code\&. .TP \fIexpanderName\fR \fBcget\fR \fIvarname\fR Retrieves the value of variable \fIvarname\fR, defined in the current context\&. .TP \fIexpanderName\fR \fBcis\fR \fIcname\fR Determines whether or not the name of the current context is \fIcname\fR\&. .TP \fIexpanderName\fR \fBcname\fR Returns the name of the current context\&. .TP \fIexpanderName\fR \fBcpop\fR \fIcname\fR Pops a context from the context stack, returning all accumulated output in that context\&. The context must be named \fIcname\fR, or an error results\&. .TP \fIexpanderName\fR \fBctopandclear\fR Returns the output currently captured in the topmost context and clears that buffer\&. This is similar to a combination of \fBcpop\fR followed by \fBcpush\fR, except that internal state (brackets) is preserved here\&. .TP \fIexpanderName\fR \fBcpush\fR \fIcname\fR Pushes a context named \fIcname\fR onto the context stack\&. The context must be popped by \fBcpop\fR before expansion ends or an error results\&. .TP \fIexpanderName\fR \fBcset\fR \fIvarname\fR \fIvalue\fR Sets variable \fIvarname\fR to \fIvalue\fR in the current context\&. .TP \fIexpanderName\fR \fBcvar\fR \fIvarname\fR Retrieves the internal variable name of context variable \fIvarname\fR; this allows the variable to be passed to commands like \fBlappend\fR\&. .TP \fIexpanderName\fR \fBerrmode\fR \fInewErrmode\fR Sets the macro expansion error mode to one of \fBnothing\fR, \fBmacro\fR, \fBerror\fR, or \fBfail\fR; the default value is \fBfail\fR\&. The value determines what the expander does if an error is detected during expansion of a macro\&. .RS .TP \fBfail\fR The error propagates normally and can be caught or ignored by the application\&. .TP \fBerror\fR The macro expands into a detailed error message, and expansion continues\&. .TP \fBmacro\fR The macro expands to itself; that is, it is passed along to the output unchanged\&. .TP \fBnothing\fR The macro expands to the empty string, and is effectively ignored\&. .RE .sp .TP \fIexpanderName\fR \fBevalcmd\fR ?\fInewEvalCmd\fR? Returns the current evaluation command, which defaults to \fBuplevel #0\fR\&. If specified, \fInewEvalCmd\fR will be saved for future use and then returned; it must be a Tcl command expecting one additional argument: the macro to evaluate\&. .TP \fIexpanderName\fR \fBexpand\fR \fIstring\fR ?\fIbrackets\fR? Expands the input string, replacing embedded macros with their expanded values, and returns the expanded string\&. .sp Note that this method pushes a new (empty) context on the stack of contexts while it is running, and removes it on return\&. .sp If \fIbrackets\fR is given, it must be a list of two strings; the items will be used as the left and right macro expansion bracket sequences for this expansion only\&. .TP \fIexpanderName\fR \fBlb\fR ?\fInewbracket\fR? Returns the current value of the left macro expansion bracket; this is for use as or within a macro, when the bracket needs to be included in the output text\&. If \fInewbracket\fR is specified, it becomes the new bracket, and is returned\&. .TP \fIexpanderName\fR \fBrb\fR ?\fInewbracket\fR? Returns the current value of the right macro expansion bracket; this is for use as or within a macro, when the bracket needs to be included in the output text\&. If \fInewbracket\fR is specified, it becomes the new bracket, and is returned\&. .TP \fIexpanderName\fR \fBreset\fR Resets all expander settings to their initial values\&. Unusual results are likely if this command is called from within a call to \fBexpand\fR\&. .TP \fIexpanderName\fR \fBsetbrackets\fR \fIlbrack rbrack\fR Sets the left and right macro expansion brackets\&. This command is for use as or within a macro, or to permanently change the bracket definitions\&. By default, the brackets are \fB[\fR and \fB]\fR, but any non-empty string can be used; for example, \fB<\fR and \fB>\fR or \fB(*\fR and \fB*)\fR or even \fBHello,\fR and \fBWorld!\fR\&. .TP \fIexpanderName\fR \fBtextcmd\fR ?\fInewTextCmd\fR? Returns the current command for processing plain text, which defaults to the empty string, meaning \fIidentity\fR\&. If specified, \fInewTextCmd\fR will be saved for future use and then returned; it must be a Tcl command expecting one additional argument: the text to process\&. The expander object will this command for all plain text it encounters, giving the user of the object the ability to process all plain text in some standard way before writing it to the output\&. The object expects that the command returns the processed plain text\&. .sp \fINote\fR that the combination of "\fBtextcmd\fR \fIplaintext\fR" is run through the \fIevalcmd\fR for the actual evaluation\&. In other words, the \fItextcmd\fR is treated as a special macro implicitly surrounding all plain text in the template\&. .TP \fIexpanderName\fR \fBwhere\fR Returns a three-element list containing the current character position, line, and column the expander is at in the processing of the current input string\&. .PP .SH TUTORIAL .SS BASICS To begin, create an expander object: .PP .CS % package require textutil::expander 1\&.2 % ::textutil::expander myexp ::myexp % .CE .PP The created \fB::myexp\fR object can be used to expand text strings containing embedded Tcl commands\&. By default, embedded commands are delimited by square brackets\&. Note that expander doesn't attempt to interpolate variables, since variables can be referenced by embedded commands: .PP .CS % set greeting "Howdy" Howdy % proc place {} {return "World"} % ::myexp expand {[set greeting], [place]!} Howdy, World! % .CE .SS "EMBEDDING MACROS" An expander macro is simply a Tcl script embedded within a text string\&. Expander evaluates the script in the global context, and replaces it with its result string\&. For example, .PP .CS % set greetings {Howdy Hi "What's up"} Howdy Hi "What's up" % ::myexp expand {There are many ways to say "Hello, World!": [set result {} foreach greeting $greetings { append result "$greeting, World!\\\\n" } set result] And that's just a small sample!} There are many ways to say "Hello, World!": Howdy, World! Hi, World! What's up, World! And that's just a small sample! % .CE .SS "WRITING MACRO COMMANDS" More typically, \fImacro commands\fR are used to create a markup language\&. A macro command is just a Tcl command that returns an output string\&. For example, expand can be used to implement a generic document markup language that can be retargeted to HTML or any other output format: .PP .CS % proc bold {} {return ""} % proc /bold {} {return ""} % ::myexp expand {Some of this text is in [bold]boldface[/bold]} Some of this text is in boldface % .CE .PP The above definitions of \fBbold\fR and \fB/bold\fR returns HTML, but such commands can be as complicated as needed; they could, for example, decide what to return based on the desired output format\&. .SS "CHANGING THE EXPANSION BRACKETS" By default, embedded macros are enclosed in square brackets, \fB[\fR and \fB]\fR\&. If square brackets need to be included in the output, the input can contain the \fBlb\fR and \fBrb\fR commands\&. Alternatively, or if square brackets are objectionable for some other reason, the macro expansion brackets can be changed to any pair of non-empty strings\&. .PP The \fBsetbrackets\fR command changes the brackets permanently\&. For example, you can write pseudo-html by change them to \fB<\fR and \fB>\fR: .PP .CS % ::myexp setbrackets < > % ::myexp expand {This is boldface} This is boldface .CE .PP Alternatively, you can change the expansion brackets temporarily by passing the desired brackets to the \fBexpand\fR command: .PP .CS % ::myexp setbrackets "\\\\[" "\\\\]" % ::myexp expand {This is boldface} {< >} This is boldface % .CE .SS "CUSTOMIZED MACRO EXPANSION" By default, macros are evaluated using the Tcl \fBuplevel #0\fR command, so that the embedded code executes in the global context\&. The application can provide a different evaluation command using \fBevalcmd\fR; this allows the application to use a safe interpreter, for example, or even to evaluated something other than Tcl code\&. There is one caveat: to be recognized as valid, a macro must return 1 when passed to Tcl's "info complete" command\&. .PP For example, the following code "evaluates" each macro by returning the macro text itself\&. .PP .CS proc identity {macro} {return $macro} ::myexp evalcmd identity .CE .SS "USING THE CONTEXT STACK" Often it's desirable to define a pair of macros which operate in some way on the plain text between them\&. Consider a set of macros for adding footnotes to a web page: one could have implement something like this: .PP .CS Dr\&. Pangloss, however, thinks that this is the best of all possible worlds\&.[footnote "See Candide, by Voltaire"] .CE .PP The \fBfootnote\fR macro would, presumably, assign a number to this footnote and save the text to be formatted later on\&. However, this solution is ugly if the footnote text is long or should contain additional markup\&. Consider the following instead: .PP .CS Dr\&. Pangloss, however, thinks that this is the best of all possible worlds\&.[footnote]See [bookTitle "Candide"], by [authorsName "Voltaire"], for more information\&.[/footnote] .CE .PP Here the footnote text is contained between \fBfootnote\fR and \fB/footnote\fR macros, continues onto a second line, and contains several macros of its own\&. This is both clearer and more flexible; however, with the features presented so far there's no easy way to do it\&. That's the purpose of the context stack\&. .PP All macro expansion takes place in a particular context\&. Here, the \fBfootnote\fR macro pushes a new context onto the context stack\&. Then, all expanded text gets placed in that new context\&. \fB/footnote\fR retrieves it by popping the context\&. Here's a skeleton implementation of these two macros: .PP .CS proc footnote {} { ::myexp cpush footnote } proc /footnote {} { set footnoteText [::myexp cpop footnote] # Save the footnote text, and return an appropriate footnote # number and link\&. } .CE .PP The \fBcpush\fR command pushes a new context onto the stack; the argument is the context's name\&. It can be any string, but would typically be the name of the macro itself\&. Then, \fBcpop\fR verifies that the current context has the expected name, pops it off of the stack, and returns the accumulated text\&. .PP Expand provides several other tools related to the context stack\&. Suppose the first macro in a context pair takes arguments or computes values which the second macro in the pair needs\&. After calling \fBcpush\fR, the first macro can define one or more context variables; the second macro can retrieve their values any time before calling \fBcpop\fR\&. For example, suppose the document must specify the footnote number explicitly: .PP .CS proc footnote {footnoteNumber} { ::myexp cpush footnote ::myexp csave num $footnoteNumber # Return an appropriate link } proc /footnote {} { set footnoteNumber [::myexp cget num] set footnoteText [::myexp cpop footnote] # Save the footnote text and its footnoteNumber for future # output\&. } .CE .PP At times, it might be desirable to define macros that are valid only within a particular context pair; such macros should verify that they are only called within the correct context using either \fBcis\fR or \fBcname\fR\&. .SH HISTORY \fBexpander\fR was written by William H\&. Duquette; it is a repackaging of the central algorithm of the expand macro processing tool\&. .SH "BUGS, IDEAS, FEEDBACK" This document, and the package it describes, will undoubtedly contain bugs and other problems\&. Please report such in the category \fItextutil\fR of the \fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&. Please also report any ideas for enhancements you may have for either package and/or documentation\&. .PP When proposing code changes, please provide \fIunified diffs\fR, i\&.e the output of \fBdiff -u\fR\&. .PP Note further that \fIattachments\fR are strongly preferred over inlined patches\&. Attachments can be made by going to the \fBEdit\fR form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar\&. .SH "SEE ALSO" [uri, http://www\&.wjduquette\&.com/expand, regexp, split, string .SH KEYWORDS string, template processing, text expansion .SH CATEGORY Documentation tools .SH COPYRIGHT .nf Copyright (c) William H\&. Duquette, http://www\&.wjduquette\&.com/expand .fi