Keywords & syntax

Quick cheat sheet for Rain syntax.

Rain is expression-oriented with C-like blocks. Statements end with ;. Blocks use { }.

Import modules with benutzen. User .rn files export every top-level binding by default: call them with module::name().

Minimal program shape

benutzen "math";

var xs = #[1, 2, 3];
print math::sqrt(16);
print xs->len();

output

4
3

Symbol	Description
`var`	Variable declaration
`fun`	Named function or anonymous `fun(params) { }` expression
`class`	Class declaration
`benutzen`	Import a built-in or `.rn` module
`if / else`	Conditional
`while`	Loop
`for`	C-style loop, `for (item von array)`, or `for (key, value von map)`
`von`	For-each: `for (item von array)` or `for (k, v von map)`
`break / continue`	Exit or skip loop iterations
`versuch / fang (try/catch)`	Try / catch runtime errors
`return`	Return from function
`print`	Output with newline
`and / or`	Logical operators
`true / false / nil`	Literals
`this`	Current instance
`super`	Superclass method call

Symbol	Description
`#[a, b, c]`	Array literal
`{"a": 1, "b": 2}`	Map literal: string keys, any values
`arr[i]`	Array index get / set
`map["key"]`	Map get / set: missing keys return nil
`map->len()`	Map method: len, keys, values, has, delete
`arr->len()`	Array method call
`obj?.field`	Optional chaining: `nil` receiver short-circuits to `nil`
`obj?.a?.b`	Chained optional access through nested instance fields
`for (x von arr)`	Iterate every element of an array
`for (k, v von map)`	Iterate every key/value pair of a map
`{}`	Empty map literal
`fun(x) { }`	Anonymous function expression
`fun(a, ...rest)`	Variadic function: `...rest` must be last; extra args become an array
`"hello #{name}"`	String interpolation: any expression inside #{...}
`\#{literal}`	Escaped hash: prints #{literal} without interpolating
`\"quote\"`	Escaped quote inside a string literal
`"a" + "b"`	String concatenation; numbers and booleans coerce to strings
`vakya(x) / toString(x)`	Global built-in: convert any value to a string
`math::sqrt(9)`	Module function call
`class Child < Parent`	Inheritance