Structure of Programs

A semi-formal representation of Polylang programs is shown below.

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For the official grammar for Polylang, please refer to this grammar file (opens in a new tab).

Grammar Notation

{x} means zero or more occurrences of x.
[x] means zero or one occurrences of x, meaning that x is optional.
(one of) followed by space-separated items indicates a choice of one of the items.
x indicates a literal of value x.

Simplified Grammar for Polylang

A polylang program ("schema") consists of one or more contract (opens in a new tab) declarations:

Schema:
    [ContractDeclaration]

where each contract consists of field declarations, a constructor declaration, and function declarations:

ContractDeclaration:
    [(one of)`@public` `@private`]
    `contract` ContractName ContractBody
 
ContractName:
    alphanumeric starting with a letter
 
ContractBody:
    {FieldDeclaration}
    [ConstructorDeclaration]
    {FunctionDeclaration}

FieldDeclaration:
    (one of)
    RequiredFieldDeclaration OptionalFieldDeclaration
 
RequiredFieldDeclaration:
    FieldName: FieldType ';'
 
OptionalFieldDeclaration:
    FieldName`?` : FieldTyoe ';'
 
FieldName:
    alphanumeric starting with a letter

where each field can have the following types:

FieldType:
    (one of)
    PrimitiveType `bytes` `PublicKey` ContractType ArrayType MapType ObjectType
 
PrimitiveType:
    (one of)
    `string` `number` `boolean`
 
ContractType:
   a reference to a contract 
 
ArrayType:
    `string`[] `number`[] `boolean`[] `PublicKey`[] ContractType[]
 
MapType:
    `map` `<`MapKeyType : FieldType `>`
 
MapKeyType:
    (one of)
    `string` `number`
 
ObjectType:
    '{' [FieldName ':' FieldType] '}'

Field types are defined in more detail here.

Constructors and functions are similar in structure. Note that the constructor keyword is mandatory for a constructor declaration:

ConstructorDeclaration:
   `constructor` ConstructorName ConstructorArgs ConstructorBody 
 
ConstructorName:
    alphanumeric starting with a letter
 
ConstructorArgs:
    '(' [ArgPair] {`,` ArgPair} ')'

ArgPair:
    ArgName ':' ArgType
 
ArgName:
    alphanumeric starting with a letter
 
ArgType:
    FieldType

Note that the function keyword in a function declaration is optional:

FunctionDeclaration:
    [`function`] FunctionName FunctionArgs FunctionBody
 
FunctionName:
    alphanumeric starting with a letter
 
FunctionArgs:
    ConstructorArgs
 
FunctionBody:
    ConstructorBody

Declarative Permissions