mirror of https://github.com/texmacs/doc.git
103 lines
4.0 KiB
Plaintext
103 lines
4.0 KiB
Plaintext
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<TeXmacs|1.0.3.10>
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<style|tmdoc>
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<\body>
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<tmdoc-title|Environment primitives>
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The current environment both defines all style parameters which affect the
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typesetting process and all additional macros provided by the user and the
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current style. The primitives in this section are used to access and modify
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environment variables.
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<\explain>
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<explain-macro|assign|var|val><explain-synopsis|variable mutation>
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<|explain>
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This primitive sets the environment variable named <src-arg|var> (string
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value) to the value of the <src-arg|val> expression. This primitive is
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used to make non-scoped changes to the environment, like defining markup
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or increasing counters.
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This primitive affects the evaluation process <emdash>through
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<markup|value>, <markup|provides>, and macro definitions<emdash> and the
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typesetting process <emdash>through special typesetter variables.
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<\example>
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Enabling page breaking by style.
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The <verbatim|page-medium> is used to enable page breaking. Since only
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the <re-index|initial environment> value for this variable is
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effective, this assignation must occur in a style file, not within a
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document.
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<\tm-fragment>
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<inactive*|<assign|page-medium|paper>>
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</tm-fragment>
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</example>
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<\example>
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Setting the chapter counter.
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The following snippet will cause the immediately following chapter to
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be number 3. This is useful to get the the numbering right in
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<verbatim|book> style when working with projects and <markup|include>.
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<\tm-fragment>
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<inactive*|<assign|chapter-nr|2>>
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</tm-fragment>
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</example>
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The operand must be a literal string and is interpreted as a file name.
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The content of this file is typeset in place of the <markup|include> tag,
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which must be placed in <re-index|block context>.
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</explain>
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<\explain>
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<explain-macro|with|var-1|val-1|<with|mode|math|\<cdots\>>|var-n|val-n|body><explain-synopsis|variable
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scope>
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<|explain>
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This primitive temporarily sets the environment variables <src-arg|var-1>
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until <src-arg|var-n> (in this order) to the evaluated values of
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<src-arg|val-1> until <src-arg|val-n> and typesets <src-arg|body> in this
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modified environment. All non-scoped change done with <markup|assign> to
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<src-arg|var-1> until <src-arg|var-n> within <src-arg|body> are reverted
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at the end of the <markup|with>.
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This primitive is used extensively in style files to modify the
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typesetter environment. For example to locally set the text font, the
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paragraph style, or the mode for mathematics.
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</explain>
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<\explain>
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<explain-macro|value|var><explain-synopsis|variable value>
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<|explain>
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This primitive evaluates the current value of the environment variable
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<src-var|var> (literal string). This is useful to display counters and
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generally to implement environment-sensitive behavior.
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This primitive is used extensively in style files to modify the
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typesetter environment. For example to locally set the text font, the
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paragraph style, or the mode for mathematics.
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</explain>
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<\explain>
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<explain-macro|provides|var><explain-synopsis|definition predicate>
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<|explain>
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This predicate evaluates to <verbatim|true> if the environment variable
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<src-var|var> (string value) is defined, and to <verbatim|false>
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otherwise.
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That is useful for modular markup, like the <markup|session>
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environments, to fall back to a default appearance when a required
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package is not used in the document.
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</explain>
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<tmdoc-copyright|2004|David Allouche|Joris van der Hoeven>
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<tmdoc-license|Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version 1.1
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or any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled "GNU Free
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Documentation License".>
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</body>
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