Modelica^® Language Specification version 3.6-dev 20 The Modelica Standard Library B Modelica DAE Representation

Appendix A Modelica Concrete Syntax

(August 19, 2021)

A.1 Lexical conventions

The following syntactic meta symbols are used (extended BNF):

Syntax	Description
[ $\ldots$ ]	Optional
{ $\ldots$ }	Repeat zero or more times
$\ldots$ \| $\ldots$	Alternatives
" $\mathit{text}$ "	The $\mathit{text}$ is treated as a single token (no white-space between any characters)

The following lexical units are defined:

⬇

IDENT = NON-DIGIT { DIGIT | NON-DIGIT } | Q-IDENT

Q-IDENT = "’" { Q-CHAR | S-ESCAPE } "’"

NON-DIGIT = "_" | letters "a"

\ldots

"z" | letters "A"

\ldots

"Z"

DIGIT = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"

Q-CHAR = NON-DIGIT | DIGIT | "!" | "#" | "$" | "%" | "&" | "(" | ")"

| "*" | "+" | "," | "-" | "." | "/" | ":" | ";" | "<" | ">" | "="

| "?" | "@" | "[" | "]" | "^" | "{" | "}" | "|" | "~" | " " | """

S-ESCAPE = "\’" | "\"" | "\?" | "\\"

| "\a" | "\b" | "\f" | "\n" | "\r" | "\t" | "\v"

STRING = """ { S-CHAR | S-ESCAPE } """

S-CHAR = see below

UNSIGNED-INTEGER = DIGIT { DIGIT }

UNSIGNED-REAL =

UNSIGNED-INTEGER "." [ UNSIGNED-INTEGER ]

| UNSIGNED_INTEGER [ "." [ UNSIGNED_INTEGER ] ]

( "e" | "E" ) [ "+" | "-" ] UNSIGNED-INTEGER

| "." UNSIGNED-INTEGER [ ( "e" | "E" ) [ "+" | "-" ] UNSIGNED-INTEGER ]

S-CHAR is any member of the Unicode character set (http://www.unicode.org; see section 13.4 for storing as UTF-8 on files) except double-quote ‘"’, and backslash ‘\’.

For identifiers the redundant escapes (‘\?’ and ‘\""’) are the same as the corresponding non-escaped variants (‘?’ and ’""’). The single quotes are part of an identifier. For example, the identifiers ’x’ and x are different.

Note:

•

White-space and comments can be used between separate lexical units and/or symbols, and also separates them. Each lexical unit will consume the maximum number of characters from the input stream. White-space and comments cannot be used inside other lexical units, except for STRING and Q-IDENT where they are treated as part of the STRING or Q-IDENT lexical unit.
•

Concatenation of string literals requires a binary expression. For example, "a" + "b" evaluates to "ab". There is no support for the C/C++ style of concatenating adjacent string literal tokens (for example, "a" "b" becoming "ab").
•

Modelica uses the same comment syntax as C++ and Java (i.e., // signals the start of a line comment and /* $\ldots$ */ is a multi-line comment); comments may contain any Unicode character. Modelica also has structured comments in the form of annotations and string comments.
•

Each description-string or string in annotations (= STRING with production annotation-clause in the grammar) may contain any member of the Unicode character set. All other strings have to contain only the subset of Unicode characters identical with the 7-bit US-ASCII character set.

[As a consequence, operators like ‘>’ or ‘<’, and external functions only operate on ASCII strings and not on Unicode-strings. Within a description-string the tags <HTML> and </HTML> or <html> and </html> define optionally begin and end of content that is HTML encoded.]
•

Boldface denotes keywords of the Modelica language. Keywords are reserved words and shall not be used as identifiers.
•

Productions use hyphen as separator both in the grammar and in the text. Previously the grammar used underscore.

A.2 Grammar

A.2.1 Stored Definition – Within

⬇

stored-definition :

[ within [ name ] ";" ]

{ [ final ] class-definition ";" }

A.2.2 Class Definition

⬇

class-definition :

[ encapsulated ] class-prefixes class-specifier

class-prefixes :

[ partial ]

( class

| model

| [ operator ] record

| block

| [ expandable ] connector

| type

| package

| [ pure | impure ] [ operator ] function

| operator

)

class-specifier :

long-class-specifier | short-class-specifier | der-class-specifier

long-class-specifier :

IDENT description-string composition end IDENT

| extends IDENT [ class-modification ] description-string composition

end IDENT

short-class-specifier :

IDENT "=" base-prefix type-specifier [ array-subscripts ]

[ class-modification ] description

| IDENT "=" enumeration "(" ( [ enum-list ] | ":" ) ")" description

der-class-specifier :

IDENT "=" der "(" type-specifier "," IDENT { "," IDENT } ")" description

base-prefix :

[ input | output ]

enum-list :

enumeration-literal { "," enumeration-literal }

enumeration-literal :

IDENT description

composition :

element-list

{ public element-list

| protected element-list

| equation-section

| algorithm-section

}

[ external [ language-specification ]

[ external-function-call ] [ annotation-clause ] ";"

]

[ annotation-clause ";" ]

language-specification :

STRING

external-function-call :

[ component-reference "=" ]

IDENT "(" [ expression-list ] ")"

element-list :

{ element ";" }

element :

import-clause

| extends-clause

| [ redeclare ]

[ final ]

[ inner ] [ outer ]

( class-definition

| component-clause

| replaceable ( class-definition | component-clause )

[ constraining-clause description ]

)

import-clause :

import

( IDENT "=" name

| name [ ".*" | "." ( "*" | "{" import-list "}" ) ]

)

description

import-list :

IDENT { "," IDENT }

A.2.3 Extends

⬇

extends-clause :

extends type-specifier [ class-modification ] [ annotation-clause ]

constraining-clause :

constrainedby type-specifier [ class-modification ]

A.2.4 Component Clause

⬇

component-clause :

type-prefix type-specifier [ array-subscripts ] component-list

type-prefix :

[ flow | stream ]

[ discrete | parameter | constant ]

[ input | output ]

component-list :

component-declaration { "," component-declaration }

component-declaration :

declaration [ condition-attribute ] description

condition-attribute :

if expression

declaration :

IDENT [ array-subscripts ] [ modification ]

A.2.5 Modification

⬇

modification :

class-modification [ "=" expression ]

| "=" expression

| ":=" expression

class-modification :

"(" [ argument-list ] ")"

argument-list :

argument { "," argument }

argument :

element-modification-or-replaceable

| element-redeclaration

element-modification-or-replaceable :

[ each ] [ final ] ( element-modification | element-replaceable )

element-modification :

name [ modification ] description-string

element-redeclaration :

redeclare [ each ] [ final ]

( short-class-definition | component-clause1 | element-replaceable )

element-replaceable :

replaceable ( short-class-definition | component-clause1 )

[ constraining-clause ]

component-clause1 :

type-prefix type-specifier component-declaration1

component-declaration1 :

declaration description

short-class-definition :

class-prefixes short-class-specifier

A.2.6 Equations

⬇

equation-section :

[ initial ] equation { equation ";" }

algorithm-section :

[ initial ] algorithm { statement ";" }

equation :

( simple-expression "=" expression

| if-equation

| for-equation

| connect-clause

| when-equation

| component-reference function-call-args

)

description

statement :

( component-reference ( ":=" expression | function-call-args )

| "(" output-expression-list ")" ":="

component-reference function-call-args

| break

| return

| if-statement

| for-statement

| while-statement

| when-statement

)

description

if-equation :

if expression then

{ equation ";" }

{ elseif expression then

{ equation ";" }

}

[ else

{ equation ";" }

]

end if

if-statement :

if expression then

{ statement ";" }

{ elseif expression then

{ statement ";" }

}

[ else

{ statement ";" }

]

end if

for-equation :

for for-indices loop

{ equation ";" }

end for

for-statement :

for for-indices loop

{ statement ";" }

end for

for-indices :

for-index { "," for-index }

for-index :

IDENT [ in expression ]

while-statement :

while expression loop

{ statement ";" }

end while

when-equation :

when expression then

{ equation ";" }

{ elsewhen expression then

{ equation ";" }

}

end when

when-statement :

when expression then

{ statement ";" }

{ elsewhen expression then

{ statement ";" }

}

end when

connect-clause :

connect "(" component-reference "," component-reference ")"

A.2.7 Expressions

⬇

expression :

simple-expression

| if expression then expression

{ elseif expression then expression }

else expression

simple-expression :

logical-expression [ ":" logical-expression [ ":" logical-expression ] ]

logical-expression :

logical-term { or logical-term }

logical-term :

logical-factor { and logical-factor }

logical-factor :

[ not ] relation

relation :

arithmetic-expression [ relational-operator arithmetic-expression ]

relational-operator :

"<" | "<=" | ">" | ">=" | "==" | "<>"

arithmetic-expression :

[ add-operator ] term { add-operator term }

add-operator :

"+" | "-" | ".+" | ".-"

term :

factor { mul-operator factor }

mul-operator :

"*" | "/" | ".*" | "./"

factor :

primary [ ("^" | ".^") primary ]

primary :

UNSIGNED-NUMBER

| STRING

| false

| true

| ( component-reference | der | initial | pure ) function-call-args

| component-reference

| "(" output-expression-list ")"

| "[" expression-list { ";" expression-list } "]"

| "{" array-arguments "}"

| end

UNSIGNED-NUMBER :

UNSIGNED-INTEGER | UNSIGNED-REAL

type-specifier :

["."] name

name :

IDENT { "." IDENT }

component-reference :

[ "." ] IDENT [ array-subscripts ] { "." IDENT [ array-subscripts ] }

function-call-args :

"(" [ function-arguments ] ")"

function-arguments :

expression [ "," function-arguments-non-first | for for-indices ]

| function-partial-application [ "," function-arguments-non-first ]

| named-arguments

function-arguments-non-first :

function-argument [ "," function-arguments-non-first ]

| named-arguments

array-arguments :

expression [ "," array-arguments-non-first | for for-indices ]

array-arguments-non-first :

expression [ "," array-arguments-non-first ]

named-arguments: named-argument [ "," named-arguments ]

named-argument: IDENT "=" function-argument

function-argument :

function-partial-application | expression

function-partial-application :

function type-specifier "(" [ named-arguments ] ")"

output-expression-list :

[ expression ] { "," [ expression ] }

expression-list :

expression { "," expression }

array-subscripts :

"[" subscript { "," subscript } "]"

subscript :

":" | expression

description :

description-string [ annotation-clause ]

description-string :

[ STRING { "+" STRING } ]

annotation-clause :

annotation class-modification