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We first define a declaration’s reach. The reach of a labeled block is the block itself. A method declaration not in an object expression or declaration must be in the declaration of some trait T , and its reach is the declaration of T and any trait or object declarations or object expressions that extend T ; that is, if the declaration of trait T contains a method declaration, and trait S extends trait T , then the reach of that method declaration includes the declaration of trait S. The reach of any other declaration is the smallest block strictly containing that declaration (i.e., not just the declaration itself). For example, the reach of a top-level declaration is the component containing that declaration, the reach of a field declaration is the enclosing object declaration or expression, the reach of a parameter declaration is the functional declaration or function expression in whose parameter list it occurs, and the reach of a local variable declaration is the smallest block in which that declaration occurs. We say that a declaration reaches any point within its reach. It is a static error for two declarations with overlapping reaches to declare the same name other than self (even if the name is declared in different namespaces) unless one of the following conditions holds: • both declarations are functional declarations with the same reach, • both declarations are method declarations that occur in different trait declarations, • one declaration is a field or keyword-parameter declaration whose reach is strictly contained in the reach of the other declaration, or • one declaration is a method declaration that is provided by (i.e., occurs in or is inherited by) some trait or object declaration or object expression that is strictly contained in the reach of the other declaration. If either of the first two conditions holds, or if one declaration is a field or method declaration that occurs in an object declaration or expression that inherits the other declaration (which therefore must be a method declaration), then the two declarations are overloaded, and subject to the restrictions on overloading (see Chapter 33). If two declarations with overlapping reaches declare the same name in the same namespace, and the declarations are not overloaded, then at any point that their reaches overlap, one declaration shadows the other for that name in that namespace; we may omit the name and namespace when it is clear from context. Shadowing is permitted only in the following cases: • In a trait or object declaration, any declaration in a block enclosing the declaration is shadowed if it declares a name of a field or method provided (declared or inherited) by the trait or object being declared. • In a method declaration that does not give an explicit name other than self for the self parameter, any declaration of self (including implicit declarations) in a block enclosing the field or method declaration is shadowed. • In the ensures clause of a contract, any declaration of result in a block enclosing the ensures clause is shadowed. • In a function or method declaration with keyword parameters, any declaration in a block enclosing the declaration is shadowed if it declares the name of any of the keyword parameters. We say that a name is in scope in a namespace at any point in the program within the reach of a declaration that declares that name in that namespace unless one of the following conditions holds: • the declaration is shadowed for the name in that namespace, • the declaration is a variable declaration, the namespace is the value namespace, and the program point is in the initial-value expression of the declaration or an initial-value expression of another declaration that is in the smallest lexical block enclosing the declaration and lexically precedes the declaration in that block. Note that the last condition applies to the method names declared by a wrapped field declaration. We say that the scope of a declaration for a name in a namespace consists of those points at which the name is in scope for the namespace and the declaration is not shadowed for that name and that namespace. Again, when it is clear from context, we may omit the name and namespace. 62
7.3 Qualified Names Fortress provides a component system in which the entities declared in a component are described by an API. A component may import APIs, allowing it to refer to these entities declared by the imported APIs. In some cases, references to these entities must be qualified by the API name. These qualified names can be used in any place that a simple name would be used had the entity been declared directly in the component rather than being imported. Note that qualified names are distinguished from simple names by the inclusion of a “ . ” token, so they never shadow, nor are they shadowed by, simple names. For further discussion on APIs and the component system, see Chapter 22. 63
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The Fortress Language Specification
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4 Evaluation 36 4.1 Values . . . .
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12 Functions 85 12.1 Function Decla
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17.7 Coercions for Tuple and Arrow
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IV Fortress for Library Writers 214
Page 11 and 12: 40.10The Trait Fortress.Core.Binary
Page 13 and 14: Chapter 1 Introduction The Fortress
Page 15 and 16: A note on the presented libraries i
Page 17 and 18: component HelloWorld export Executa
Page 19 and 20: foo:String → () baz: String → S
Page 21 and 22: fortress upgrade Gary with Ralph No
Page 23 and 24: halve(x : R64) : R64 = x/2 Predicta
Page 25 and 26: while x < 10 do print x x += 1 end
Page 27 and 28: It is also possible to convert a me
Page 29 and 30: factorial(n) = ∏ i←1:n i This f
Page 31 and 32: In both methods cons and append , t
Page 33 and 34: default distributions will provide
Page 35 and 36: Chapter 3 Programs A program consis
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Page 41 and 42: Chapter 5 Lexical Structure A Fortr
Page 43 and 44: U+0021 EXCLAMATION MARK ! U+0023 NU
Page 45 and 46: If a character (or any other syntac
Page 47 and 48: BIG SI unit absorbs abstract also a
Page 49 and 50: escape sequences are useful for ASC
Page 51 and 52: 5.14.1 Multicharacter Enclosing Ope
Page 53 and 54: Note: the elegant way to write Avog
Page 55 and 56: • top-level variable declarations
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Page 59 and 60: several new variables. This syntax
Page 61: Chapter 7 Names Names are used to r
Page 65 and 66: Fortress also allows coercion betwe
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Page 69 and 70: TypeAlias ::= type Id [StaticParams
Page 71 and 72: ‘}’. If such a clause contains
Page 73 and 74: Note that a trait declaration inher
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Page 77 and 78: Chapter 10 Objects An object is a v
Page 79 and 80: FldDef ::= FldMod ∗ Id [IsType] (
Page 81 and 82: Chapter 11 Static Parameters Trait,
Page 83 and 84: 11.5 Operator and Identifier Parame
Page 85 and 86: Chapter 12 Functions Functions are
Page 87 and 88: swap(x :Object, y : Object) = (y, x
Page 89 and 90: A function declaration may be separ
Page 91 and 92: Chapter 13 Expressions Fortress is
Page 93 and 94: Negating the literal 0 produces a s
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Page 97 and 98: 13.10 Assignments Syntax: Expr ::=
Page 99 and 100: treeSum(t : TreeLeaf) = 0 treeSum(t
Page 101 and 102: Several common mathematical operato
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Page 107 and 108: An atomic expression consists of th
Page 109 and 110: 13.26 Try Expressions Syntax: Flow
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A = [1 2 3; 4 5 6; 7 8 9] then A 1,
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evaluates to the set {0, 4, 16} Map
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ignore(f x) is equivalent to: f x;
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trait CheckedException extends { Ex
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Chapter 15 Overloading and Multiple
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e called with. In other words, we e
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Chapter 16 Operators Operators are
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• “ordinary” operators: + −
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left context whitespace operator fi
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The rules below are designed to for
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16.8.3 Enclosing Operators When use
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16.8.9 Intersection, Union, and Set
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Chapter 17 Conversions and Coercion
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17.3 Coercion Invocations One may i
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arguments nor with variable number
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trait B extends A end trait C exten
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a new coercion in a subexpression
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for tokens. For readability, plural
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Chapter 19 Tests and Properties For
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19.5 Test Suites In order to allow
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Chapter 20 Type Inference Type infe
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3. If a i is a functional applicati
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21.2 Programming Discipline If Fort
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Here the call f(a, a) ends up setti
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2. Ancestors, dynamically ordered b
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The ways in which fortresses are ac
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Component equivalence is determined
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22.5 Type Inference for Components
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Fortress.IO Fortress.Crypto IronLin
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execute(componentName:String, args:
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3. If the replacement does not expo
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This method runs all test functions
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Fortress.IO Fortress.Crypto Fortres
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Part III Fortress APIs and Document
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23.1.3 hash(maxval: N64): N64 23.1.
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opr =(self,other: Boolean):Boolean
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24.1.20 getter hashCode(): N64 24.1
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False: BooleanInterval Uncertain: B
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24.2.11 opr ∧(self,other: Boolean
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24.2.19 possibly(self): Boolean 24.
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Chapter 25 Numbers 25.1 Rational Nu
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opr ⌈self ⌉: N realpart(self):
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25.1.11 opr (self,other: Q):Boolean
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25.1.26 floor(self): Z 25.1.27 opr
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Chapter 26 Negated Relational Opera
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26.1.26 opr ⊀T extends BinaryPred
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27.3 The Trait Fortress.Standard.Un
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Chapter 29 Dimensions and Units 29.
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unit secondOfAngle secondsOfAngle:
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Chapter 30 Tests 30.1 The Object Fo
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31.2 Convenience Types An optional
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Chapter 32 Parallelism and Locality
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y evaluating the two elements of th
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There is a DefaultDistribution whic
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v = spawn at a.region(i) do a i end
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expr ∑ type wrapper ∑ body R,
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32.8.3 Using Overloading to Adapt G
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Chapter 33 Overloaded Functional De
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coercions: T U ⇐⇒ T ♦ U ∧
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The More Specific Rule for Function
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An infix/multifix operator declarat
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may be so defined except ordinary p
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and here some of these computed dim
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unit name 1 name 2 name 3 : . . . u
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Chapter 36 Support for Domain-Speci
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Because syntax expanders are define
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Part V Fortress APIs and Documentat
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property ∀(a:T) ¬(a ∼ a) end A
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trait PartialOrderOperatorsT extend
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The HasMinimalElement trait specifi
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The trait Commutative requires the
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A value e is a left identity for a
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trait ApproximatelyHasInverses T ex
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end extends { ApproximateCommutativ
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A default definition is provided fo
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trait RationalQuantityunit U absorb
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(self,other:RationalQuantityU,ninf
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38.2.4 getter hashCode(): Z64 38.2.
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Chapter 39 Components and APIs We d
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Chapter 40 Memory Sequences and Bin
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updatenat k(j: IntegerStatick, v: T
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40.1.12 update(j:IndexInt, v: T): L
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40.3.2 opr nat m[r:RangeOfStaticSiz
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40.5 The Trait Fortress.Core.Binary
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40.5.5 bit(m:IndexInt): Bit The res
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40.6 The Trait Fortress.Core.Binary
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40.6.4 opr nat m[r:RangeOfStaticSiz
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40.6.16 opr ‖ nat m,bool bigEndia
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countLeadingZeroBits():IndexInt cou
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40.7.41 signedShift(j:IndexInt):T 4
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40.8.6 signedDivide(other: T,overfl
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littleEndian():BinaryEndianLinearEn
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40.9.16 opr ‖ nat m,nat radix,nat
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v: BinaryEndianWordb,bigEndianBytes
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40.10.9 opr nat m[r:RangeOfStaticSi
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40.10.24 splitnat b ′ () : Binary
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itAnd(selfStart: IndexInt,source:T,
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40.13.2 wrappingAdd(selfStart: Inde
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40.13.30 unsignedMax(selfStart: Ind
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40.13.55 gatherBits(selfStart:Index
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Appendix A Fortress Calculi A.1 Bas
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Values, evaluation contexts, redexe
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Expression typing: p; ∆; Γ ⊢ e
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α, β type variables f method name
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Function/method name lookup: Fname(
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One owner for all the visible metho
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Traits defining a method: defining
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Values, evaluation contexts, and re
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Valid function declarations: p ⊢
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Method definition lookup: visible p
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Values, intermediate expressions, e
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Field typing: p; ∆; Γ ⊢ vd ok
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Appendix B Overloaded Functional De
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Proof. We prove this for δ, but th
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Upgrade A predicate upg? takes two
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a is rendered as a foobar is render
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• If a portion is sub and another
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supercalifragilisticexpialidocious
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any alternative names, with undersc
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Appendix F Operator Precedence, Cha
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U+007C VERTICAL LINE | | U+2016 DOU
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The following two operators have th
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U+003D EQUALS SIGN = = EQ U+2243 AS
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U+22DD EQUAL TO OR GREATER-THAN U+2
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U+2289 NEITHER A SUPERSET OF NOR EQ
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F.4.8 Miscellaneous Relational Oper
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U+21A5 UPWARDS ARROW FROM BAR U+21A
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U+2224 DOES NOT DIVIDE ∤ U+2225 P
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U+27F8 LONG LEFTWARDS DOUBLE ARROW
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U+2960 UPWARDS HARPOON WITH BARB LE
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U+29ED BLACK CIRCLE WITH DOWN ARROW
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Appendix G Concrete Syntax In this
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Extends ::= extends TraitTypes Excl
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StaticParam ::= Id [Extends] [absor
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Value ::= Literal | fn ValParam [Is
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Appendix H Generated Concrete Synta
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-> fn_decl -> object_decl -> var_de
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-> id extends_opt absorbs_opt -> "n
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-> w "excludes" w type_ref_list com
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-> obj_decl_body_elem br obj_decl_b
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-> op wr op_follows_op_w -> op wr e
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-> no_space_op_expr_result no_space
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id_opt -> -> w id with_opt -> -> w
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-> unpasting_elem rect_separator un
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-> "}" comprehension -> set_compreh
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-> do_expr -> for_expr -> spawn_exp
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-> type_ref -> "(" w type_ref w ","
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enc -> enc_literal op_or_enc -> op
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Bibliography [1] O. Agesen, L. Bak,
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