README.Rmd

---
output:
  md_document:
    variant: markdown_github
---

<!-- README.md is generated from README.Rmd. Please edit that file -->

```{r, echo = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.path = "README-"
)
```

# terser

A natural and terse syntax of function declaration in R for people who are interested in
shooting yourself in the foot :gun:.

You can use `f(x, y) = x + y` to define a function `f`.

```{r include=FALSE}
library(terser)
```

```{r}
f(x, y) = x + y
f(3, 4)
```


![](https://user-images.githubusercontent.com/9980776/38043325-64bae8ec-32e9-11e8-955c-b7fbae468212.gif)

> How... ?

> Yes! I overwrite the `=` operator.

If the left hand side is a symbol, it just does normal assignment like the `<-` operator.
If the left hand side is a function call, it defines a function.

Some more examples:

```{r}
x = 3
x

f(x, y) = x + y
f(2, 3)
identical(f, function(x, y) x + y)

g(x = 231) = log(x)
g()
identical(g, function(x = 231) log(x))

h(a, b = a^2) = a + b
h(1)
h(1, 2)
identical(h, function(a, b = a^2) a + b)

tan2(a) = sin(a)/cos(a)
tan2(pi)

`∑`(...) = sum(...)
`∑`(2, 3, 4)
```


## Warning

The operator `=` can no longer do assignment for attributes and elements, the following
will no longer work. Use `<-` instead.

```{r, eval=FALSE}
names(x) = c("a", "b", "c")
x[[2]] = 32
```

## See also

This package is inspired by a syntax for defining a function in Julia.

```
julia> f(x, y) = x + y
f (generic function with 1 method)
```