Type-C Basics

In this chapter, we introduce the basics of Type-C, such as identifiers, keywords, literals, program structure, etc. Some of the things we go through here are more in-depth as others, this is for simplicity reasons as things such as datatypes also have a chapter dedicated to them.

Identifiers

Identifiers in Type-C serve as names for variables, functions, types, and other entities. An identifier is a sequence of letters, digits, and underscores, starting with a letter or an underscore. Here are the exact rules of variable names:

• Must start with a letter (either uppercase or lowercase) or an underscore (_).

• Can contain letters, numbers, and underscores.

• Cannot contain special characters like #, \$, %, etc.

• Cannot be a reserved keyword.

• Are case-sensitive; for example, myVariable and myvariable are distinct identifiers.

• Follows the following regular expression pattern: ^[a-zA-Z_][a-zA-Z0-9_]*$

Examples of Valid Identifiers:

Examples of Invalid Identifiers:

Naming Conventions

In Type-C, clear and consistent naming conventions are essential for code readability and maintenance. The following conventions are established:

• Variables: Employ camelCase for variable names. For instance, localVariable.
• Constants: Use uppercase with underscores for constants, typically global compile-time constants. Example: MAX_SIZE.
• Methods: Adopt camelCase for method names. When a method is overloaded for different types, use an underscore to separate the method name from the type descriptor, then continue in camelCase. For general methods: calculateTotal(), and for type-specific methods: add_u8(), add_u16(), add_Object().
• Types: Utilize PascalCase for type names. For example, UserDetails. This is important especially for algebraic types (variants), which when used with pattern matching, a capital letter symbol will match to a datatype.
• Modules and Packages: Maintain lowercase letters and concatenate words. For example, networkutils.

Keywords

The following words are reserved keywords in Type-C and cannot be used as identifiers: as, as!, as?, break, cfn, class, const, continue, coroutine, do, else, enum, extern, false, fn, for, foreach, from, if, import, in, interface, is, let, match, mut, mutate, new, null, return, static, strict, struct, this, true, type, unreachable, variant, while, yield, yield!.

Punctuation

Type-C doesn't require semicolons. The compiler will complain if it find a semi-colon unless it is part of the grammar, in cases such as for loops.

Operators and Symbols

In Type-C, operators are fundamental constructs that perform various types of operations on variables and values. Symbols, on the other hand, serve as special characters that are part of the language's syntax. Below, we categorize and describe these elements.

Arithmetic Operators

• + Addition
• - Subtraction
• * Multiplication
• / Division
• % Modulus

Comparison Operators

• == Equal to
• != Not equal to
• < Less than
• <= Less than or equal to
• > Greater than
• >= Greater than or equal to

Logical Operators

• && Logical AND
• || Logical OR
• ! Logical NOT

Bitwise Operators

• & Bitwise AND
• | Bitwise OR
• ^ Bitwise XOR
• << Bitwise left shift
• >> Bitwise right shift
• ~ Bitwise NOT

Assignment Operators

• = Assignment
• += Add and assign
• -= Subtract and assign
• *= Multiply and assign
• /= Divide and assign

Keyword Operators

• spawn Spawning a process
• await Await a Promise
• new Class/Process allocator and consturctor
• is Type checking
• as Type casting

Other Operators

• ! Denull operator, returns a non-nullable version of a nullable type.
• ?. Nullable member access operator.
• ++ Increment
• -- Decrement

Special Symbols

• ;, :, ,, ., ..., (, ), [, ], {, } Punctuation and delimiters

• => Arrow for pattern matching

• -> Arrow used in type signatures

• _ Underscore, used in pattern matching (wild card) and as a discard symbol

As for whitespace, including spaces, tabs, and newline characters, are used to separate tokens and are generally ignored by the compiler. A practice in type-c is to use whitespaces instead of tabs, 4 whitespaces is the recommended value of indentation.

Comments

Comments in type-c follows same rules as C-family language like Java, C and C++. They come in two types:

• Single line comments: They start with // and spans for the rest of the line.

• Multi-line comments: They start with two characters /* and end at the very first occurrence of the enclosing comments */. Multiline comments cannot be nested.

Additionally, comments are a robust source of documentation if used properly. Even though Type-C currently lacks a Doxygen-style parser for automated documentation, a standard commenting style for code documentation is encouraged. This helps in maintaining readability and lays the foundation for future automated documentation parsing. The recommended style is as follows:

Example:

Literals

Literals represent constant values such as numbers or strings. Strings start with double quotes "Hello, world!" or a single quote 'Hello, type-c!'. Any string literal with a single quote and only one character is considered a char type, e.g., 'c', 'r', '\n'. The rest are strings such as "hello", "c". Escape characters in string and character literals allow for the representation of special characters within the text. The available escape characters are:

• \\ - Backslash
• \' - Single quote
• \" - Double quote
• \n - Newline
• \t - Horizontal tab
• \r - Carriage return
• \xhh - Byte by hexadecimal
• \uXXXX - Unicode code point below 10000 hexadecimal
• \UXXXXXXXX - Unicode code point where each X is a hexadecimal digit
• b"value" - Byte string literal, array of u8

Regular string literals are upcasted to standard String class, which supports utf8 encoding, some times you need a C style string, meaning as a bytearray, hence you can use byte string literals b"im just a u8[]".

Numbers are divided into three categories: single-precision floating-point numbers, double-precision floating-point numbers, and decimals. A single-precision float is a number that may or may not include a floating point but ends with f, such as 3.14f or 42f. A double float is a float that doesn't have a suffix, for example, 42.2. The overall regular expression for matching floats is: [+|-]?(?:[0-9]*)(?:\.[0-9]+)(?:[e|E]-[0-9]+)?f?. A regular decimal would be represented through simple numbers like 42. It's possible to write numbers not only in decimal but also in binary, octal, and hexadecimal. Binary values are prefixed with 0b, such as 0b0010. Octal numbers are prefixed with 0o, and hexadecimal numbers are prefixed with 0x. Note that the prefix is case-sensitive for all these cases.

On the other hand, boolean literals are represented by the reserved keywords true and false. They are of type bool and can take on only these two values. null is also a literal (and a type!). Null can only be assigned to memory referenced objects, i.e structs and objects.

Program Structure

A standard type-c program is generally organized into several key components. The structure ensures clean code separation and easier module integration. Here's what to expect in a typical file:

1. Module Imports: This is always the starting point of any type-c file. Importing modules must be the first action. While not mandatory, if present, must exclusively occupy the beginning of a type-c file.

2. Type Declarations: Unlike some languages that allow inline type declarations, type-c insists on global type declarations. This architectural choice facilitates easy type imports across different modules.

3. Function Declarations: This section is devoted to defining functions. Note that only named functions are considered here, as anonymous functions and lambda expressions are technically treated as variables.

4. Global Variables: While they are often considered harmful, global variables are allowed. However, it's strongly recommended to limit their mutability. Your code, your rules, but you've been warned.

This overview serves as a blueprint. Each of these components will be dissected and discussed in the following sections.

Importing Modules

The first logical step in most programs is to import modules. Type-C does not provide support for folders as packages, meaning, you must always import from within a Type-C file. Unlike some other languages, you're only allowed to import modules at the beginning of your file; once you declare a variable, function, or type, you can no longer perform imports. For instance, from our hello world example, the default package, std, is a folder containing various files such as io.tc. It's essential to note that nested imports don't propagate. If program A imports library B, which in turn imports library C, library C is not implicitly imported into A.

You can import datatypes and functions. Global variables are not allowed.

Variable Declarations:

Basic Declarations

In Type-C, variables must be explicitly typed unless they can be inferred from the context. Here's a basic example:

Type inference isn't automatic for literals, so either the type must be explicitly declared, or the value must be cast:

Casting as a function call, like u32(1), is permitted only for basic data types. This feature simplifies working with literals and type conversions.

Multiple Declarations

Multiple variables can be declared in a single statement, which can be useful for code organization:

Immutability

Immutability is enforced using the const keyword:

Once declared as immutable, the variable can't be reassigned:

Nested Declarations

Type-C supports scoping within expressions using nested let declarations:

Variables declared within the inner let are only available inside its scope, which allows for cleaner, functional-style programming.

Destructuring

Destructuring is a feature that allows unpacking arrays or structs into individual variables:

It's important to note that the compiler does not check if the size of the array matches the number of variables you are trying to destructure into. This check is performed at runtime, and a runtime error (Invalid Index) will occur if the sizes do not match. Therefore, it's the programmer's responsibility to ensure that the destructuring is valid given the size of the array. Destructuring feature works for structs as well, making it highly versatile:

Immutability Consequences

Immutable variables are 'read-only', their state and the states of their components can't be modified:

Immutable variables are restrictive but secure. Using them in a function where mutability is expected will result in a compile-time error. Note that type-c doesn't enforce deep immutability, meaning if an immutable variable x for example, holds a reference to another object y, which is also referenced by a mutable variable z, the state of x can still be altered if z was to change. Immutability is enforced from the root object, but not recursively.

Function Declarations

Functions in Type-C are defined using the fn keyword, followed by the function name and its parameters. Once declared, these functions are immutable, meaning they can't be reassigned.

Function Parameters and Return Types

By default, function arguments are immutable because Type-C encourages functional purity. Attempting to modify an argument without explicitly declaring it mutable with the mut keyword will result in a compile-time error. The return type of a function is denoted by the -> symbol.

Expression Bodies

Functions can be defined with an expression body, providing a concise way to define simple functions. The return type is optional and is inferred if not provided.

Also, if a function has a block-body and no return type, it is presumed to return void by default.

Generic Functions

Functions can also be defined as generic, parameterized over types. Type checking is deferred until the generic types are concretized. Note that generic functions can't be passed as arguments or invoked unless their type parameters are explicitly specified.