Appendix A. Language Grammar

The grammar is fed from the output of lexical analysis. The tokens returned from lexical analysis are

ATTRIBUTE CONST BOOL FLOAT INT
BREAK CONTINUE DO ELSE FOR IF DISCARD RETURN
BVEC2 BVEC3 BVEC4 IVEC2 IVEC3 IVEC4 VEC2 VEC3 VEC4
MAT2 MAT3 MAT4 IN OUT INOUT UNIFORM VARYING
SAMPLER1D SAMPLER2D SAMPLER3D
SAMPLERCUBE SAMPLER1DSHADOW SAMPLER2DSHADOW
STRUCT VOID WHILE

IDENTIFIER TYPE_NAME FLOATCONSTANT INTCONSTANT BOOLCONSTANT
FIELD_SELECTION
LEFT_OP RIGHT_OP
INC_OP DEC_OP LE_OP GE_OP EQ_OP NE_OP
AND_OP OR_OP XOR_OP MUL_ASSIGN DIV_ASSIGN ADD_ASSIGN
MOD_ASSIGN LEFT_ASSIGN RIGHT_ASSIGN AND_ASSIGN XOR_ASSIGN OR_ASSIGN
SUB_ASSIGN

LEFT_PAREN RIGHT_PAREN LEFT_BRACKET RIGHT_BRACKET
LEFT_BRACE RIGHT_BRACE DOT
COMMA COLON EQUAL SEMICOLON BANG DASH TILDE PLUS STAR SLASH PERCENT
LEFT_ANGLE RIGHT_ANGLE VERTICAL_BAR CARET AMPERSAND QUESTION

The following describes the grammar for the OpenGL Shading Language in terms of the preceding tokens.

variable_identifier:

  • IDENTIFIER

primary_expression:

  • variable_identifier

  • INTCONSTANT

  • FLOATCONSTANT

  • BOOLCONSTANT

  • LEFT_PAREN expression RIGHT_PAREN

postfix_expression:

  • primary_expression

  • postfix_expression LEFT_BRACKET integer_expression RIGHT_BRACKET

  • function_call

  • postfix_expression DOT FIELD_SELECTION

  • postfix_expression INC_OP

  • postfix_expression DEC_OP

integer_expression:

  • expression

function_call:

  • function_call_generic

function_call_generic:

  • function_call_header_with_parameters RIGHT_PAREN

  • function_call_header_no_parameters RIGHT_PAREN

function_call_header_no_parameters:

  • function_call_header VOID

  • function_call_header

function_call_header_with_parameters:

  • function_call_header assignment_expression

  • function_call_header_with_parameters COMMA assignment_expression

function_call_header:

  • function_identifier LEFT_PAREN

function_identifier:

  • constructor_identifier

  • IDENTIFIER

// Grammar Note: Constructors look like functions, but lexical analysis recognized most of them as keywords.

constructor_identifier:

  • FLOAT

  • INT

  • BOOL

  • VEC2

  • VEC3

  • VEC4

  • BVEC2

  • BVEC3

  • BVEC4

  • IVEC2

  • IVEC3

  • IVEC4

  • MAT2

  • MAT3

  • MAT4

  • TYPE_NAME

unary_expression:

  • postfix_expression

  • INC_OP unary_expression

  • DEC_OP unary_expression

  • unary_operator unary_expression

// Grammar Note: No traditional style type casts.

unary_operator:

  • PLUS

  • DASH

  • BANG

  • TILDE // reserved

// Grammar Note: No ‘*’ or ‘&’ unary ops. Pointers are not supported. multiplicative_expression:

  • unary_expression

  • multiplicative_expression STAR unary_expression

  • multiplicative_expression SLASH unary_expression

  • multiplicative_expression PERCENT unary_expression // reserved

additive_expression:

  • multiplicative_expression

  • additive_expression PLUS multiplicative_expression

  • additive_expression DASH multiplicative_expression

shift_expression:

  • additive_expression

  • shift_expression LEFT_OP additive_expression // reserved

  • shift_expression RIGHT_OP additive_expression // reserved

relational_expression:

  • shift_expression

  • relational_expression LEFT_ANGLE shift_expression

  • relational_expression RIGHT_ANGLE shift_expression

  • relational_expression LE_OP shift_expression

  • relational_expression GE_OP shift_expression

equality_expression:

  • relational_expression

  • equality_expression EQ_OP relational_expression

  • equality_expression NE_OP relational_expression

and_expression:

  • equality_expression

  • and_expression AMPERSAND equality_expression // reserved

exclusive_or_expression:

  • and_expression

  • exclusive_or_expression CARET and_expression // reserved

inclusive_or_expression:

  • exclusive_or_expression

  • inclusive_or_expression VERTICAL_BAR exclusive_or_expression // reserved

logical_and_expression:

  • inclusive_or_expression

  • logical_and_expression AND_OP inclusive_or_expression

logical_xor_expression:

  • logical_and_expression

  • logical_xor_expression XOR_OP logical_and_expression

logical_or_expression:

  • logical_xor_expression

  • logical_or_expression OR_OP logical_xor_expression

conditional_expression:

  • logical_or_expression

  • logical_or_expression QUESTION expression COLON assignment_expression

assignment_expression:

  • conditional_expression

  • unary_expression assignment_operator assignment_expression

assignment_operator:

  • EQUAL

  • MUL_ASSIGN

  • DIV_ASSIGN

  • MOD_ASSIGN // reserved

  • ADD_ASSIGN

  • SUB_ASSIGN

  • LEFT_ASSIGN // reserved

  • RIGHT_ASSIGN // reserved

  • AND_ASSIGN // reserved

  • XOR_ASSIGN // reserved

  • OR_ASSIGN // reserved

expression:

  • assignment_expression

  • expression COMMA assignment_expression

constant_expression:

  • conditional_expression

declaration:

  • function_prototype SEMICOLON

  • init_declarator_list SEMICOLON

function_prototype:

  • function_declarator RIGHT_PAREN

function_declarator:

  • function_header

  • function_header_with_parameters

function_header_with_parameters:

  • function_header parameter_declaration

  • function_header_with_parameters COMMA parameter_declaration

function_header:

  • fully_specified_type IDENTIFIER LEFT_PAREN

parameter_declarator:

  • type_specifier IDENTIFIER

  • type_specifier IDENTIFIER LEFT_BRACKET constant_expression RIGHT_BRACKET

parameter_declaration:

  • type_qualifier parameter_qualifier parameter_declarator

  • parameter_qualifier parameter_declarator

  • type_qualifier parameter_qualifier parameter_type_specifier

  • parameter_qualifier parameter_type_specifier

parameter_qualifier:

  • /* empty */

  • IN

  • OUT

  • INOUT

parameter_type_specifier:

  • type_specifier

  • type_specifier LEFT_BRACKET constant_expression RIGHT_BRACKET

init_declarator_list:

  • single_declaration

  • init_declarator_list COMMA IDENTIFIER

  • init_declarator_list COMMA IDENTIFIER LEFT_BRACKET RIGHT_BRACKET

  • init_declarator_list COMMA IDENTIFIER LEFT_BRACKET constant_expression RIGHT_BRACKET

  • init_declarator_list COMMA IDENTIFIER EQUAL initializer

single_declaration:

  • fully_specified_type

  • fully_specified_type IDENTIFIER

  • fully_specified_type IDENTIFIER LEFT_BRACKET RIGHT_BRACKET

  • fully_specified_type IDENTIFIER LEFT_BRACKET constant_expression RIGHT_BRACKET

  • fully_specified_type IDENTIFIER EQUAL initializer

// Grammar Note: No ‘enum’ or ‘typedef’.

fully_specified_type:

  • type_specifier

  • type_qualifier type_specifier

type_qualifier:

  • CONST

  • ATTRIBUTE // Vertex only.

  • VARYING

  • UNIFORM

type_specifier:

  • VOID

  • FLOAT

  • INT

  • BOOL

  • VEC2

  • VEC3

  • VEC4

  • BVEC2

  • BVEC3

  • BVEC4

  • IVEC2

  • IVEC3

  • IVEC4

  • MAT2

  • MAT3

  • MAT4

  • SAMPLER1D

  • SAMPLER2D

  • SAMPLER3D

  • SAMPLERCUBE

  • SAMPLER1DSHADOW

  • SAMPLER2DSHADOW

  • struct_specifier

  • TYPE_NAME

struct_specifier:

  • STRUCT IDENTIFIER LEFT_BRACE struct_declaration_list RIGHT_BRACE

  • STRUCT LEFT_BRACE struct_declaration_list RIGHT_BRACE

struct_declaration_list:

  • struct_declaration

  • struct_declaration_list struct_declaration

struct_declaration:

  • type_specifier struct_declarator_list SEMICOLON

struct_declarator_list:

  • struct_declarator

  • struct_declarator_list COMMA struct_declarator

struct_declarator:

  • IDENTIFIER

  • IDENTIFIER LEFT_BRACKET constant_expression RIGHT_BRACKET

initializer:

  • assignment_expression

declaration_statement:

  • declaration

statement:

  • compound_statement

  • simple_statement

// Grammar Note: No labeled statements; ‘goto’ is not supported.

simple_statement:

  • declaration_statement

  • expression_statement

  • selection_statement

  • iteration_statement

  • jump_statement

compound_statement:

  • LEFT_BRACE RIGHT_BRACE

  • LEFT_BRACE statement_list RIGHT_BRACE

statement_no_new_scope:

  • compound_statement_no_new_scope

  • simple_statement

compound_statement_no_new_scope:

  • LEFT_BRACE RIGHT_BRACE

  • LEFT_BRACE statement_list RIGHT_BRACE

statement_list:

  • statement

  • statement_list statement

expression_statement:

  • SEMICOLON

  • expression SEMICOLON

selection_statement:

  • IF LEFT_PAREN expression RIGHT_PAREN selection_rest_statement

selection_rest_statement:

  • statement ELSE statement

  • statement

// Grammar Note: No ‘switch’. Switch statements not supported.

condition:

  • expression

  • fully_specified_type IDENTIFIER EQUAL initializer

iteration_statement:

  • WHILE LEFT_PAREN condition RIGHT_PAREN statement_no_new_scope

  • DO statement WHILE LEFT_PAREN expression RIGHT_PAREN SEMICOLON

  • FOR LEFT_PAREN for_init_statement for_rest_statement RIGHT_PAREN statement_no_new_scope

for_init_statement:

  • expression_statement

  • declaration_statement

conditionopt:

  • condition

  • /* empty */

for_rest_statement:

  • conditionopt SEMICOLON

  • conditionopt SEMICOLON expression

jump_statement:

  • CONTINUE SEMICOLON

  • BREAK SEMICOLON

  • RETURN SEMICOLON

  • RETURN expression SEMICOLON

  • DISCARD SEMICOLON // Fragment shader only.

// Grammar Note: No ‘goto’. Gotos are not supported.

translation_unit:

  • external_declaration

  • translation_unit external_declaration

external_declaration:

  • function_definition

  • declaration

function_definition:

  • function_prototype compound_statement_no_new_scope

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