Syntax

Comments

Oba has line comments, only, which start with // and end on a newline:

// This is a comment

Reserved words

debug false let true if else while match fn import

Identifiers

Identifiers start with an underscore or letter and contain letters, digits, and underscores. Examples:

_i
camelCase
PascalCase
_snake_case
alph4num3r1c
ALL_CAPS

Newlines

Oba does not have semicolons, except for in special cases. Instead, newlines (\n) are used to terminate statements:

system::print("hello")
system::print("there")

Newlines in the middle of statements are ignored to allow long statements to be broken across multiple lines:

call_function_with_many_args(
  arg0, arg1, arg2, arg3, arg4,
  arg5, arg6, arg7, arg8, arg9
)

Blocks

Blocks are used to create nested scopes and are delimited by curly braces. They are used as the bodies of functions, if-statements and loops. Some examples:

{
  // x is a local variable in this block's scope.
  let x = 1
}

if (true) {
  // This is a different local variable named 'x'.
  let x = 2;
}

while (true) {
  // Yet another unique 'x'.
  let x = 3;
}

fn foo {
  let x = 4; // You get the idea...
}

Strings

Oba strings are surrounded by double-quotes and can span newlines:

"This is a string"

"This
is
also
a
string
"

Values can be interpolated within strings using %() notation:

import "system"

let a = 1;
let b = 2;

system::print("%(a) + %(b) = %(a + b)") // Prints: 1 + 2 = 3

The interpolated expression can span multiple lines as well. This prints the same thing as the above example:

system::print("%(a) + %(b) = %(
a + b
)")

Strings also support the following escape characters:

Character	Description
`\%`	Percent sign
`\\`	Backslash
`\r`	Carriage return
`\n`	Newline
`\"`	Double quotation

Precedence and associativity

Oba has both prefix and infix operators. Unary operators such as the “not” operator ! are always right-associative. Binary operators such as +-*/ are always left-associative. The full set of operators is described in the table below:

Precedence	Operators	Description	Associativity
1	! =	Not, Assignment	Right
2	< > <= >= != ==	Comparison	Left
3	+ - %	Add,Subtract,Mod	Left
4	/ *	Multiply,Divide	Left
5	::	Membership	Left

Grammar

declaration   = data
              | statement
              | import
data          | 'data' IDENT '=' constructor ('|' constructor)*
import        = 'import' STRING
statement     = functionDefn
              | variableDecl
              | debugStmt
              | blockStmt
              | ifStmt
              | whileStmt
              | expression
constructor   | IDENTGG
functionDefn  = 'fn' IDENT parameterList functionBody
variableDecl  = 'let' IDENT '=' expression
debugStmt     = 'debug' expression
blockStmt     = '{' declaration* '}'
ifStmt        = 'if' expression statement ('else' statement)?
whileStmt     = 'while' expression statement
expression    = grouping
              | PREFIX_OP expression
              | TERM INIFIX_OP expression
grouping      = '(' expression* ')
parameterList = IDENT*
functionBody  = expression
              | blockStmt
TERM          = IDENT
              | NUMBER
              | STRING
              | functionCall
functionCall  = IDENT '(' (expression ','?)* ')'
IDENT         = ([a-zA-Z_][a-zA-Z_0-9]*) ('::' IDENT)*
STRING        = '"' [^'"']* '"'
NUMBER        = [0-9]+
PREFIX_OP     = '!'
INIFIX_OP     = '+' '-' '*' '/'

Reference

Language