Juxtaposition means combine in the obvious way: Difference between revisions
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[[Category:Unspoken conventions]] | |||
[[Category:Ambiguities]] | |||
In an expression, putting two things immediately next to each other usually means that they should be combined in some way. It's usually implicit that the combination operation should be clear from the context. | In an expression, putting two things immediately next to each other usually means that they should be combined in some way. It's usually implicit that the combination operation should be clear from the context. | ||
==Examples== | |||
* [[Missing multiplication symbol|Multiplication]]: \(ab = a \times b\). | * [[Missing multiplication symbol|Multiplication]]: \(ab = a \times b\). | ||
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* Group operation: when \(x,y \in G = (X,\star)\), \(xy = x \star y\). | * Group operation: when \(x,y \in G = (X,\star)\), \(xy = x \star y\). | ||
* A linear transformation: \(\mathrm{A}\mathbf{v}\). (I've never seen \(\mathrm{A} \times \mathbf{v}\) or \(\mathrm{A} \cdot \mathbf{v}\) for matrix-vector product) | * A linear transformation: \(\mathrm{A}\mathbf{v}\). (I've never seen \(\mathrm{A} \times \mathbf{v}\) or \(\mathrm{A} \cdot \mathbf{v}\) for matrix-vector product) | ||
==Exceptions== | |||
* [[Matrix indices|Matrix indices written without a comma]]. | |||
==Unicode== | |||
There are Unicode symbols U+2062 INVISIBLE TIMES and U+2061 FUNCTION APPLICATION, both invisible. Christian Lawson-Perfect claims he can tell when you don't use them<ref>[https://somethingorotherwhatever.com/twitter-archive/status/1321409295473352705/ Tweet by Christian Lawson-Perfect]</ref>. | |||
==References== | |||
<references/> | |||
Latest revision as of 14:05, 22 May 2026
In an expression, putting two things immediately next to each other usually means that they should be combined in some way. It's usually implicit that the combination operation should be clear from the context.
Examples
- Multiplication: \(ab = a \times b\).
- Function composition: \(fg(x) = f \circ g(x) = f(g(x))\).
- Function application: \(\sin x\).
- Group operation: when \(x,y \in G = (X,\star)\), \(xy = x \star y\).
- A linear transformation: \(\mathrm{A}\mathbf{v}\). (I've never seen \(\mathrm{A} \times \mathbf{v}\) or \(\mathrm{A} \cdot \mathbf{v}\) for matrix-vector product)
Exceptions
Unicode
There are Unicode symbols U+2062 INVISIBLE TIMES and U+2061 FUNCTION APPLICATION, both invisible. Christian Lawson-Perfect claims he can tell when you don't use them[1].