SIMPLE-4-Declarations

Language "SIMPLE"

#4 Declarations

Syntax  
  Decl : decl ::= vars-decl | func-decl

Semantics
  declare[[ _:decl ]] : =>environments

## 4.1 Variable Declarations


Syntax
  VarsDecl : vars-decl ::= 'var' declarators ';'

  Declarators : declarators ::= declarator (',' declarators)^?

Rule

  [[ 'var' Declarator ','       Declarators ';' Stmts^? ]] : stmts =
  [[ 'var' Declarator ';' 'var' Declarators ';' Stmts^? ]]
Rule
  [[ 'var' Declarator ','       Declarators ';' Decls^? ]] : decls =
  [[ 'var' Declarator ';' 'var' Declarators ';' Decls^? ]]

Rule
  declare[[ 'var' Declarator ';' ]] = var-declare[[ Declarator ]]


Syntax
  Declarator : declarator ::= id
                           |  id '=' exp
                           |  id ranks

Semantics
  var-declare[[ _:declarator ]] : =>environments

Rule

  var-declare[[ Id ]] = bind(id[[ Id ]], allocate-variable(values))
Rule
  var-declare[[ Id '=' Exp ]] =
  	bind(id[[ Id ]], allocate-initialised-variable(values, rval[[ Exp ]]))
Rule
  var-declare[[ Id Ranks ]] =
  	bind(id[[ Id ]], allocate-nested-vectors(ranks[[ Ranks ]]))

## 4.2 Arrays


Syntax
  Ranks : ranks ::= '[' exps ']' ranks^?

Rule

  [[ '[' Exp ',' Exps ']' Ranks^?     ]] : ranks =
  [[ '[' Exp ']' '[' Exps ']' Ranks^? ]]


// Compare this with p28 of the K version. 
Semantics
  ranks[[ _:ranks ]] : (=>nats)⁺

Rule

  ranks[[ '[' Exp ']' ]] = rval[[ Exp ]]
Rule
  ranks[[ '[' Exp ']' Ranks ]] = rval[[ Exp ]] , ranks[[ Ranks ]]


Funcon
  allocate-nested-vectors(_:nats⁺) : =>variables

Rule

  allocate-nested-vectors(N:nats) ~>
  	allocate-initialised-variable(vectors(variables),
  	  vector(left-to-right-repeat(allocate-variable(values),1,N)))
Rule
  allocate-nested-vectors(N:nats,N⁺:nats⁺) ~>
  	allocate-initialised-variable(vectors(variables),
  	  vector(left-to-right-repeat(allocate-nested-vectors(N⁺),1,N)))

## 4.3 Function Declarations


Syntax
  FuncDecl : func-decl ::= 'function' id '(' ids^? ')' block

Rule

  declare[[ 'function' Id '(' Ids^? ')' Block ]] =
    bind(id[[ Id ]], 
      allocate-variable(functions(tuples(values*),values)))


Semantics
  initialise[[ _:decl ]] : =>null-type

Rule

  initialise[[ 'var' Declarators ';' ]] = null
Rule
  initialise[[ 'function' Id '(' Ids^? ')' Block ]] =
  	assign(
  	  bound(id[[ Id ]]),
  	  function closure(
  	    scope(
  	  	  match(given,tuple(patts[[ Ids^? ]])),
          handle-return(exec[[ Block ]]))))


Syntax
  Ids : ids ::= id (',' ids)^?

Semantics
  patts[[ _:ids^? ]] : patterns*

Rule

  patts[[ ]] = ( )
Rule
  patts[[ Id ]] = 
 	pattern closure(bind(id[[ Id ]], 
  	                  allocate-initialised-variable(values, given)))
Rule
  patts[[ Id ',' Ids ]] =
    patts[[ Id ]] , patts[[ Ids ]]