rexagon / usl

Useless scripting language

USL - useless scripting language

Syntax definition

program = general_statement*

general_statement = function_declaration | statement

statement = while_loop | 
            do_while_loop | 
            for_loop | 
            branch | 
            block |
            variable_declaration SEMICOLON | 
            expression SEMICOLON 

function_declaration = KW_FUNCTION ID function_arguments function_block
function_arguments = PAR_O function_arg_id (COMMA function_arg_id)* PAR_C
function_arg_id = [KW_REF] ID
function_block = BR_O function_statement* BR_C
function_statement = statement | KW_RETURN [expression] SEMICOLON

while_loop = KW_WHILE condition loop_block
do_while_loop = KW_DO loop_block condition

for_loop = KW_FOR for_condition loop_block
for_condition = PAR_O [variable_declaration] SEMICOLON [expression] SEMICOLON [expression] PAR_C

loop_block = BR_O loop_statement* BR_C
loop_statement = statement | KW_BREAK SEMICOLON | KW_CONTINUE SEMICOLON

branch = KW_IF condition block [branch_else]
branch_else = KW_ELSE block

condition = PAR_O expression PAR_C
block = BR_O statement* BR_C

variable_declaration = KW_LET ID [OP_ASSIGN expression]

expression = logical_or_expression |
             (unary_expression OP_ASSIGN expression)

logical_or_expression = logical_and_expression |
                        logical_or_expression OP_OR logical_and_expression

logical_and_expression = equality_expression |
                         logical_and_expression OP_AND equality_expression


equality_expression = relational_expression |
                      equality_expression OP_EQ relational_expression |
                      equality_expression OP_NEQ relational_expression

relational_expression = additive_expression |
                        relational_expression OP_LT additive_expression |
                        relational_expression OP_LEQ additive_expression |
                        relational_expression OP_GT additive_expression |
                        relational_expression OP_GEQ additive_expression

additive_expression = multiplicative_expression |
                      additive_expression OP_ADD multiplicative_expression |
                      additive_expression OP_MINUS multiplicative_expression

multiplicative_expression = unary_expression |
                            multiplicative_expression OP_MUL unary_expression |
                            multiplicative_expression OP_DIV unary_expression

unary_expression = postfix_expression |
                   OP_INC unary_expression |
                   OP_DEC unary_expression |
                   OP_PLUS unary_expression |
                   OP_MINUS unary_expression |
                   OP_NEG unary_expression

postfix_expression = primary_expression |
                     postfix_expression OP_INC |
                     postfix_expression OP_DEC |
                     postfix_expression STRUCT_REF ID |
                     postfix_expression PAR_O call_arguments PAR_C

primary_expression = ID | NULL | BOOL | NUMBER | STRING | PAR_O expression PAR_C

call_arguments = [expression (COMMA expression)*]

KW_LET = "let"
KW_IF = "if"
KW_ELSE = "else"
KW_WHILE = "while"
KW_DO = "do"
KW_FOR = "for"
KW_BREAK = "break"
KW_CONTINUE = "continue"
KW_FUNCTION = "function"
KW_RETURN = "return"
KW_REF = "ref"

NULL = "null"
BOOL = 'true" | "false"
ID = /[a-zA-Z_]+/
STRING = /"(\\.|[^"])*"/
NUMBER = /-?[0-9]+\.?[0-9]*/

OP_ASSIGN = "="
OP_OR = "||"
OP_AND = "&&"
OP_EQ = "=="
OP_NEQ = "!="
OP_LT = "<"
OP_LEQ = "<="
OP_GT = ">"
OP_GEQ = ">="
OP_PLUS = "+"
OP_MINUS = "-"
OP_MUL = "*"
OP_DIV = "/"
OP_INC = "++"
OP_DEC = "--"
OP_NEG = "!"

STRUCT_REF = "."
PAR_O = "("
PAR_C = ")"
BR_O = "{"
BR_C = "}"
COMMA = ","
SEMICOLON = ";"

COMMENT_SL = ///*$"/
COMMENT_ML = //\**.\*//

Generating project

Ensure latest versions of CMake and C++ compiler are installed.

mkdir build && cd build
cmake ..

# On Windows use
cmake --build . --config Release

# On Linux use
make