A length is a measure of distance. Many LaTeX commands take
a length as an argument.
\newlength: Define a new length.
\setlength: Set the value of a length.
\addtolength: Add a quantity to a length.
\settodepth: Set a length to the depth of something.
\settoheight: Set a length to the height of something.
\settowidth: Set a length to the width of something.
Predefined lengths: Lengths that are, like, predefined.
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\newlength ::newlength::
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\newlength{\gnat}
The \newlength command defines the mandatory argument, \gnat,
as a length command with a value of 0in. An error occurs if a
\gnat command already exists.
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\setlength ::setlength::
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\setlength{\gnat}{length}
The \setlength command is used to set the value of a length
command. The length argument can be expressed in any terms
of length LaTeX understands, i.e., inches (in),
millimetres (mm), points (pt), etc.
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\addtolength ::addtolength::
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\addtolength{\gnat}{length}
The \addtolength command increments a "length command" by the
amount specified in the length argument. It can be a negative
amount.
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\settodepth ::settodepth::
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\settodepth{\gnat}{text}
The \settodepth command sets the value of a length command
equal to the depth of the text argument.
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\settoheight ::settoheight::
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\settoheight{\gnat}{text}
The \settoheight command sets the value of a length command
equal to the height of the text argument.
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\settowidth ::settowidth::
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\settowidth{\gnat}{text}
The \settowidth command sets the value of a length command
equal to the width of the text argument.
These length parameters can be used in the arguments of the
box-making commands
See section Spaces & Boxes.
They specify the natural width etc. of the text in the box.
\totalheight equals \height + \depth. To make a box with the
text stretched to double the natural size, e.g., say
