deertree/specs.org

GRU DeerTree specifications

GRU DeerTree standard library specifications

DeerTree is high-level programming language, focused on simplification of low-level development.

Lexical items

Comments

• One line comment starts with // and ends with a newline.
• Multiple lines comment starts with /* and ends with */.

Tokens

• Token is minimal language unit in DeerTree.
• There several types of tokens in DeerTree: identifiers, keywords and punctuation.

Identifiers

• Identifiers are program elements.
• Keywords can't be used as identifiers.

Keywords

• Keywords are predefined and reserved words.
• They are associated with specific features.

DeerTree keywords:

fn, import, int, double, long, float, char, byte,
string, bool, true, false, return, if, else, const,
switch, case, for, do, while, break, continue, struct,
enum, union, type, goto, unsigned, extern, strict

(auto), (until), (define) -- this is not needed

Punctuation

• Punctutation is character sequence that represents operators and punctuation.

DeerTree punctuation:

'+', '-', '*', '/', '%', '++', '--'
'&', '&&', '|', '||', '^', '<<', '>>',
'+=', '-=', '*=', '/=', '%=', '&=', '|=', '^=',
'>', '>=', '<', '<=', '=', '==', '!', '~'
'(', ')', '{', '}', '[', ']', ',', '.', ';', ':'

Integer literals

• An integer literal is sequence of digits that represents integer contstant.
• Prefix before integer literal sets non-decimal base of it: 0b or 0B - binary, 0o or 0O - octal, 0x or 0X - hexadecimal.
• Underscores don't change literal value, if they are after base prefix. Underscores can't be before integer literal or after.

Integer literals examples:

123
12_34
0b0101010
0B0101010
0o20
0O20
0xff
0xFF
0Xff
0XFF
0xFF_FF_FF

_12 // invalid: handled as identifier
12_ // invalid: can't be in the end of integer literal, must separate digits
12__34 // invalid: there can't be two underscores in a row
0_xff // invalid: underscore can't be in base prefix

Float literals

• A floating-point literal is a decimal or hexadecimal representation of a floating-point constant.
• A decimal floating-point literal consists of an integer part (decimal digits), a decimal point, a fractional part (decimal digits), and an exponent part (e or E followed by an optional sign and decimal digits).
• A hexadecimal floating-point literal consists of a 0x or 0X prefix, an integer part (hexadecimal digits), a radix point, a fractional part (hexadecimal digits), and an exponent part (p or P followed by an optional sign and decimal digits).
• Underscores don't change literal value, if they are after base prefix. Underscores can't be before float literal or after.

Integer literals examples:

0.
12.34
1.23456
1.e+10
3_4.

Rune literals

• A rune literal represents a rune constant, an integer value identifying a Unicode code point.
• A rune literal is expressed as one or more characters enclosed in single quotes, as in 'x' or '\n'.
• Within the quotes, any character may appear except newline and unescaped single quote.
• Single quoted character represents the Unicode value of the character itself, while multi-character sequences beginning with a backslash encode values in various formats.

After backslash, certain single-character escapes represent special values

\a   U+0007 alert or bell
\b   U+0008 backspace
\f   U+000C form feed
\n   U+000A line feed or newline
\r   U+000D carriage return
\t   U+0009 horizontal tab
\v   U+000B vertical tab
\\   U+005C backslash
\'   U+0027 single quote  (valid escape only within rune literals)
\"   U+0022 double quote  (valid escape only within string literals)

Rune literals examples

'a'
'\n'
'\000'
'\xFFF'
'aa' // invalid: too many characters

String literals

• A string literal represents a string constant.
• A string is sequence of characters.
• The text between the quotes forms the value of the literal, with backslash escapes interpreted as rune literals.

String literals examples

"a"
"aaa"
"\n"
"\""
"Hello, World\n"

TODO Constants

Variables

• A variable is a location for storing a value.
• Variables have types.
• Each element of array acts as a variable.

Variables examples

int a;
float b;
char[] c;
int a = 12;
a = 34;
b = 56;
a = b;

TODO Types

• A type can be defined using type command.

Boolean types

• A boolean type represents the set of Boolean truth values denoted by the predeclared constants true and false.
• bool is predeclared boolean type.

Numeric types

• A numeric type represents a set of integer or floating-point values.

Predeclared numeric types

// TODO: unsigned and others
int    - 32-bit integer
double - 64-bit integer
long   - 64-bit integer
float  - 32-bit floating-point numbers
char   - 8-bit integer
byte   - alias for char

String types

• A string type represents the set of string values
• A string value is a (possibly empty) sequence of character
• string is predeclared string type

Array types

Function types

Dictionary types

TODO Declarations

Label scopes

Constant declarations

Type declarations

Variable declarations

[type] [var-name];
[type] [var-name] = [value];

Function declarations

• A function declaration binds an identifier to function as function name

fn [function-name] '(' { arguments_list } ')' { '(' { type } ')' } '{' body '}'

Example

fn inc_number(int num) (int) {
  return num+1;
}

TODO Expressions

TODO Statements

Empty statements

Labeled statements

[identifier] ':' body

Expression statements

expression

Increment/Decrement statements

expression ( "++" | "--" )

Assignments

[identifier] ( '+=' | '-=' | '*=' | '/=' | '%=' | '|=' | '^=' | '&=' | '=' ) expression

If statements

"if" '(' condition ')' '{' body '}' ( ( "else if" | "else" ) )

switch statements

"switch" '(' expression ')' '{' ( "case" expression | "else" ) body '}'

for statements

"for" '(' condition ')' '{' body '}'

while statements

"while" '(' condition ')' '{' body '}'

return statements

• "return" statement terminates execution of function and provided result values.

return { expression }

break statements

"break"

continue statements

"continue"

goto statements

• "goto" statement transfers control to statement with corresponding label

goto [label]

TODO Built-in functions

sizeof()

len()

compare()

Printing functions

print();

println();

fprint();

fprintln()

sprint();

sprintln()

eprint();

eprintln()

Converting functions

int()

float()

char()

str()

TODO Headers