# Usages of Unicode symbols


```{julia}
#| echo: false

import Logging
Logging.disable_logging(Logging.Info) # or e.g. Logging.Info
Logging.disable_logging(Logging.Warn)

import SymPy
function Base.show(io::IO, ::MIME"text/html", x::T) where {T <: SymPy.SymbolicObject}
    println(io, "<span class=\"math-left-align\" style=\"padding-left: 4px; width:0; float:left;\"> ")
    println(io, "\\[")
    println(io, sympy.latex(x))
    println(io, "\\]")
    println(io, "</span>")
end

# hack to work around issue
import Markdown
import CalculusWithJulia
function CalculusWithJulia.WeaveSupport.ImageFile(d::Symbol, f::AbstractString, caption; kwargs...)
    nm = joinpath("..", string(d), f)
    u = "![$caption]($nm)"
    Markdown.parse(u)
end

nothing
```

`Julia` allows the use of *Unicode* symbols to replace variable names and for function calls. Unicode operations are entered in this pattern `\name[tab]`. That is a slash, `\`, the name (e.g., `alpha`), and then a press of the `tab` key.


In these notes, the following may appear as variable or function names


| `\Name`  | Symbol | Usage notes                     |
|:-------- |:------ |:------------------------------- |
| `\euler` | `ℯ`    | The variable `e`                |
| `\pi`    | `π`    |                                 |
| `\alpha` | `α`    |                                 |
| `\beta`  | `β`    |                                 |
| `\delta` | `δ`    |                                 |
| `\Delta` | `Δ`    | Change, as in `Δx`              |
| `\gamma` | `γ`    |                                 |
| `\phi`   | `ϕ`    |                                 |
| `\Phi`   | `Φ`    | Used for parameterized surfaces |
| `x\_1`   | `x₁`   | Subscripts                      |
| `r\vec`  | `r⃗`   | Vector annotation               |
| `T\hat`  | `T̂`   | Unit vector annotation          |


The following are associated with derivatives


| `\Name`    | Symbol | Usage notes                 |
|:---------- |:------ |:--------------------------- |
| `\partial` | `∂`    |                             |
| `\nabla`   | `∇`    | del operator in CwJ package |


The following are *infix* operators


| `\Name`  | Symbol | Usage notes   |
|:-------- |:------ |:------------- |
| `\circ`  | `∘`    | composition   |
| `\cdot`  | `⋅`    | dot product   |
| `\times` | `×`    | cross product |


Infix operators may need parentheses due to precedence rules. For example, to call a composition, one needs `(f ∘ g)(x)` so that composition happens before function evaluation (`g(x)`).