Changes

ConTeXt allows different methods to initialize variables and to calculate with dimension units{{note|This article is about the data type. For the names of a page's many dimensions, see [[Layout]].}}

=== \definemeasure === \setupexternalfigures[location={localA dimension,globalin TeX,default}]is a variable storing a length. The length is entered \definemeasure[ColumnC][30mm]as a number immediately followed by two letters that indicate the unit, e.g. \definemeasure[ColumnD][40mm] \definemeasure[ColumnCD][\the\dimexpr(\measure{ColumnC}+\measure{ColumnDcode|12pt})\relax] C \measure{ColumnC} D \measureor {ColumnD} CD \measure{ColumnCDcode|1cm} \externalfigure[cow][width=\measure{ColumnCD}]. TeX recognizes 9 different units:

=== \defineexpandable === \setupexternalfigures[location={local* scaled points ('''sp'''), equal to 1/65536 points. This is TeX's internal unit for dimensions. One sp is so small that TeX can store dimensions as integers; at the time,globalthis was an advantage,default}]because floating point arithmetic was not guaranteed to be consistent across platforms. * points ('''pt''') and picas ('''pc'''). One point is 1/72.27 inch; 12 points = 1 pica. \defineexpandable\ColumnA {30mm}* didot ('''dd''') and cicero ('''cc'''). The didot is a continental counterpart of the point; 12 didot = 1 cicero. \defineexpandable\ColumnB {40mm}* big points ('''bp'''), defined by Adobe as 1/72 of an inch. \defineexpandable\ColumnAB {\the\dimexpr* millimeters ('''mm'''), centimeters ('''cm'''), and inches (\ColumnA + \ColumnB'''in''')\relax} A \ColumnA B \ColumnB AB: \ColumnAB \externalfigure[cow][width=\ColumnAB].

\defineexpandable\.{{tex|newdimen}} is the native TeX method to initialise a dimension variable.The requirement to explicitly initialize your dimension variables is a bit clunky, but this method should still be preferred over [[#Storing dimensions as strings|storing dimensions as strings]]. same as * {{tex|newdimen}} is by far the lowlevel-TeX-Macro \more common idiom* Values stored in a dimension register with {{cmd|newdimen}} can be accessed directly from Lua, which is not true for values stored in a macro with {{tex|def\..}} or {{cmd|definemeasure}}.

<context mode="mkiv" source== \newdimen === \setupexternalfigures[location={local,global,default}] "yes"> \defineexpandable\ColumnA {30mm} \defineexpandable\ColumnB {40mm} \newdimen\ColumnAB \ColumnAB=\dimexpr(\ColumnA + \ColumnB) columnA % initialise variable A \ColumnA B \ColumnB ColumnAB: \the\ColumnAB \externalfigure[cow][widthcolumnA=\the\ColumnAB]\externalfigure ist also working without "\the".10mm % set variable

=== Column A is \ctxlua === \setupexternalfigures[location={local,global,default}] \defineexpandable\ColumnA {30mm} \defineexpandable\ColumnB {40mm} \defineexpandablethe\ColumnABii columnA{\ctxlua{context([==[\ColumnA + \ColumnB]==])}} ColumnABii: \the\dimexpr \ColumnABii\relaxwide. % lengths are automatically \externalfigure[cow][width=\dimexpr(\ColumnABii)\relax] % displayed in pt.

=== Offene Fragen === Column A is \number\the expandcolumnA sp wide. % internally, lengths are stored \relax % as an integer number of sp

\blackrule[width=\columnA]</context> == Defining and accesing dimensions in Lua == How to rewrite TeX code <texcode>\the\dimexpr\availablehsize\relax %say, 426pt</texcode> Mostly LMTX: <context mode="mkxl" source="yes"> 1: \number\dimexpr\availablehsize\relax 2: \startluacode token.set_macro(tex.ctxcatcodes,"temp","\\scratchdimen\\availablehsize") token.expand_macro("temp") context(tex.getdimen("scratchdimen"))\stopluacode 3: \startluacode token.set_macro(tex.ctxcatcodes,"temp","\\scratchdimen\\availablehsize") tex.runlocal("temp") context(tex.getdimen("scratchdimen"))\stopluacode 4: \startluacode tex.print("\\scratchdimen\\availablehsize") tex.pushlocal() tex.poplocal() context(tex.getdimen("scratchdimen"))\stopluacode 5: \startluacode tex.print("\\dimensiondef\\temp\\availablehsize") tex.pushlocal() tex.poplocal() context(tex.getdimensionvalue("temp"))\stopluacode \def\calculateavailablehsize{\dimensiondef\temp\availablehsize} 6: \startluacode token.expand_macro("calculateavailablehsize") context(tex.getdimensionvalue("temp"))\stopluacode \newtoks\tcalculateavailablehsize\tcalculateavailablehsize{\dimensiondef\temp\availablehsize} 7: \startluacode -- mkiv tex.runtoks("tcalculateavailablehsize") context(tex.getdimensionvalue("temp"))\stopluacode</context> == Converting dimensions == Usually, you will want to express a dimension in something other than points orscaled points. For this, Lua is the way to go:  * If you want to print, the functions {{code|number.tocentimeters}}, {{code|topoints}}, {{code|topicas}}, etc. are already provided. These functions return a number as a string with (by default) the unit abbreviation appended. * If you want to calculate, the conversion factors from standard points are stored in {{code|number.dimenfactors}}. For example, {{code|65536 * number.dimenfactors[Category"pt"]}} returns {{code|1}}. <context source=yes>\newdimen\columnA % initialise variable\columnA=10mm % set variable \startluacode local A = tex.dimen.columnA -- access a dimen value  -- internal unit: scaled points (integer) context("Column A is %d scaled points", A) context.par()  -- default conversion:ConTeXt15 digits, unit at the end, no space context("Column A is %s", number.tocentimeters(A)) context.par()  --Issuesexpressing a dimen in cm, rounded to 0.01, no automatic unit context("Column A is %s cm", number.tocentimeters(A, "%.2f")) context.par()  -- converting from mm to cm local inmm = 10 local incm = inmm / number.dimenfactors["mm"]* number.dimenfactors["cm"] context("Column A is %.1f cm", incm)\stopluacode</context> == Calculating with dimensions == From TeX, you can compute with dimensions by writing your calculation between {{tex|dimexpr}}{{code|...}}{{tex|relax}}. Such an expression may only occur where a length is expected. Spaces are allowed, but never required. <context mode=mkiv source=yes>\newdimen\columnA\columnA=1cm 0.5 cm equals \the\dimexpr \columnA / 2 \relax. \blackrule[width=\dimexpr 2 \columnA\relax]</context> In Lua, dimensions are a number of scaled points, and you can do all the usual things. TeX uses integers for dimens, but Lua treats them as floats; the number will only be coerced to integer when you retrieve from, or assign to, {{code|tex.dimen.somevalue}}. Not that half a scaled point is much to worry about. <context mode=mkiv source=yes>\newdimen\columnA\columnA=1cm \startluacode local A = tex.dimen.columnA double_A = 2 * A context.blackrule({width = double_A .. "sp"})\stopluacode</context> ;More examples: <context mode=mkiv source=yes> \newdimen\AAA \AAA=100pt \newdimen\BBB \BBB=\AAA  AAA is \the\AAA  BBB is \the\BBB</context> == Storing dimensions as strings == Because TeX expands macros, we can store a dimension string like {{code|10pt}}in a macro, and insert that in any place TeX expects a dimension. You can use a plain {{tex|def}}; or you can define dimensions with {{cmd|definemeasure|[...]}} and retrieve them with {{cmd|measure|{...}|}}. <context mode=mkiv source=yes>\definemeasure[One][10mm]\def\Two{20mm} \definemeasure[Three][\dimexpr \measure{One} + \Two\relax] \blackrule[width=\measure{One}] \crlf\blackrule[width=\Two] \crlf\blackrule[width=\measure{Three}]\crlf</context> == Conversion table == Bold numbers indicate conversions that are set by definition. {| class="wikitable"|-! unit !! TeX name! in sp !! in pt !! in pc !! in dd !! in cc! in bp !! in in !! in mm !! in cm|-| scaled point || {{code|sp}}| 1 || '''1/65536''' || || ||| || || || |-| point || {{code|pt}}| '''65536''' || 1 || '''1/12''' || 0.9346 || 0.0779| 0.9963 || '''1/72.27''' || 0.3516 || 0.0351|-| pica || {{code|pc}}| 786432 || '''12''' || 1 || 11.2149 || 0.9346| 11.9552 || 0.1660 || 4.2175 || 0.4218|-| didot || {{code|dd}}| 70124.081 || 1.0700 || 0.0892 || 1 || '''1/12'''| 1.0660 || 0.0148 || 0.3761 || 0.0376|-| cicero || {{code|cc}}| 841488.98 || 12.8401 || 1.0700 || '''12''' || 1| 12.7921 || 0.1777 || 4.5128 || 0.45128|-| big point || {{code|bp}}| 65781.76 || 1.0038 || 0.0836 || 0.9381 || 0.0782| 1 || '''1/72''' || 0.3528 || 0.0353|-| inch || {{code|in}}| 4736286.7 || '''72.27''' || 6.0225 || 67.5415 || 5.6284| '''72''' || 1 || 25.4 || 2.54|-| millimeter || {{code|mm}}| 186467.98 || 2.8453 || 0.2371 || 2.6591 || 0.2216| 2.8346 || 0.0394 || 1 || 0.1|-| centimeter || {{code|cm}}| 1864679.8 || 28.4528 || 2.3711 || 26.5911 || 2.2159| 28.3464 || 0.39370 || 10 || 1|-|} == See also ==* {{cmd|definemeasure}}* {{cmd|measure}} [[Category:Programmingand Databases]][[Category:Tools]]