272 lines
4.1 KiB
Markdown
272 lines
4.1 KiB
Markdown
# Fun Language Specification v0.1
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**Fun (Fun Uses Nothing)** is a lightweight, multi-purpose programming language designed for clarity, safety, and—above all—fun.
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This document defines the language syntax and semantics as of version 0.1.
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## 1. Introduction
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Fun is a scripting and systems programming language inspired by the best ideas from C, Lua, and Python—yet deliberately strict in its rules to ensure readability and consistency.
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- **Readable**: fixed indentation rules, no ambiguous syntax.
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- **Strict**: type safety, no implicit coercion, no silent shadowing.
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- **Hackable**: strong system integration with safe defaults.
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- **Fun**: simple enough to learn in a day, expressive enough for real work.
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## 2. Lexical Structure
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### Case Sensitivity
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Fun is **case-sensitive**. `Fun` and `fun` are different identifiers.
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### Identifiers
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- May contain `a–z`, `A–Z`, `0–9`, and `_`.
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- Must not start with a number.
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### Keywords
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Reserved words cannot be redefined:
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`if`, `else`, `for`, `while`, `fi`, `f`, `global`, `private`, `return`, `true`, `false`.
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### Comments
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- Single-line:
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// This is a comment
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- Multi-line:
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/*
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This is
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a multi-line comment
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*/
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### Whitespace
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- Indentation is exactly two spaces.
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- Tabs are forbidden.
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- Line breaks terminate statements (no semicolons).
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## 3. Data Types
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### Number
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- 64-bit signed integer.
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```
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number n = 42
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```
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### Float
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- 64-bit IEEE floating point.
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```
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float pi = 3.14159
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```
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### String
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- Double or single quotes may be used.
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- ' has higher priority, so " can appear unescaped inside '...'.
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- To include ' inside '...', escape with \'.
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```
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string s1 = "Hello"
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string s2 = 'World'
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string s3 = "He said: 'Fun!'"
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```
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### Boolean
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- Canonical values: true, false.
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- 1 and 0 are accepted in conditionals.
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```
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boolean flag = true
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```
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### Byte
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- Raw byte value.
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```
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byte b1 = 0x23
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byte b2 = "A"
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```
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### Array
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- Declared using [ ... ].
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```
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array nums = [1, 2, 3]
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```
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## 4. Variables and Scope
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- Global variables: accessible everywhere.
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- Private variables: file-local, cannot be used outside the file.
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- Redefining globals or shadowing names is forbidden.
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```
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global string message = "Hello"
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private number count = 42
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```
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## 5. Operators
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- Arithmetic: + - * / %
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- Comparison: == != > < >= <=
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- Boolean: && || !
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- Assignment: =
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## 6. Control Flow
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### If/Else
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```
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if(x != y)
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print x
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else if(a == b || h != i)
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print a + b
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else
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if(k < 1 && l > 1)
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print "Buh!"
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fi
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fi
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```
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### For Loops
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```
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for i in range(1, 10)
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print i
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```
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### While Loops
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```
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while x < 10
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print x
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x = x + 1
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```
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## 7. Functions
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### Internal Functions
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Provided by the runtime (cannot be redefined). Examples:
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print, range, system, exec.
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```
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print "Hello, Fun!"
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```
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### User-Defined Functions
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Must be declared with the f prefix.
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```
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f add(a, b)
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return a + b
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```
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### Return Values
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- Scalars: return a + b
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- Arrays: return [a, b, c]
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## 8. Modules & Includes
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### System Includes
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Looked up in /var/lib/fun/, supporting .so (native) and .fun (Fun code).
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```
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#include crypt/md5
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#include date
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#include math
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```
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### Local Includes
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From the current working directory:
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```
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#include utils/file.fun
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```
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### Absolute Includes
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Full path:
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```
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#include /home/user/project/lib.fun
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```
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## 9. System Integration
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### system
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Executes a command, returns exit code.
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```
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system("ls -l")
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```
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### exec
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Executes a command, returns stdout.
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```
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string result = exec("date")
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```
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### spawn
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Executes a command asynchronously, returns process ID.
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```
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number pid = spawn("sleep 10")
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```
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## 10. Error Handling
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- No implicit type coercion.
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- Redefinition of globals is a compile-time error.
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- Using undefined variables or functions is an error.
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- Internal/runtime functions cannot be shadowed.
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## 11. Examples
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### Hello World
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```
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print "Hello, World!"
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```
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### Loop with Range
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```
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for i in range(1, 5)
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print i
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```
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### User Function
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```
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f greet(name)
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return "Hello " + name
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print greet("Fun")
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```
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### System Call
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```
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string now = exec("date")
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print "Current time: " + now
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```
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## 12. License
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This document and the Fun language reference are licensed under the Apache License 2.0
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