The Fortress Language Specification - CiteSeerX

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test s : SetZ = {−2000, 0, 1, 7, 42, 59, 100, 1000, 5697} test fIsMonotonicOverS[x ← s, y ← s] = fIsMonotonic(x, y) test fIsMonotonicHairy[x ← s, y ← s] = fIsMonotonic(x, x 2 + y) The test fIsMonotonicOverS tests that function f is monotonic over all values in set s . The test fIsMonotonicHairy tests that f is monotonic with respect to the values in s compared to the set of values corresponding to all the ways in which we can choose an element of s , square it, and add it to another element of s . 152
Chapter 20 Type Inference Type inference in Fortress is performed independently on each simple component (described in Chapter 22). For separation of concerns, in this chapter, we describe the Fortress type inference as a procedure performed over a whole Fortress program. We explain how this procedure can be adapted to perform type inference over a simple program component in Section 22.5. Note that type inference cannot be performed on each functional (function or method) declaration in isolation because it may be declared mutually recursively or may contain free variables. 20.1 What Is Inferred Types of functional parameters, functional results, and variables may be elided in a program where they can be inferred automatically. Similarly, instantiations of static parameters of generic functional invocations may be elided where they can be inferred automatically. A Fortress compiler must allow types and static arguments inferable via the procedure described in Section 20.2 to be elided, no more and no less. This strict requirement is made for the sake of source-code portability; it is important that a program that compiles on one compiler will compile on all compilers. Of course, there is nothing preventing a development environment from aiding programmers by performing more sophisticated analyses and filling in additional information, but the text produced is not a valid Fortress program unless all elided types and static arguments can be inferred via the described procedure. 20.2 Type Inference Procedure To perform type inference, we first infer any elided parameter type in each functional declaration that can be inferred from other declaration as follows: 1. If the declaration is a functional declaration and the type of the declared functional is declared via a separate declaration, any elided parameter type is inferred to have the type provided by the separate declaration. 2. Otherwise, if the declaration is a method declaration that overloads a method declaration provided by a supertrait, any elided parameter type is inferred to have the type provided (or inferred) by the overloaded method declaration. All remaining parameter types are inferred along with instantiations of static parameters. In the following, we adopt the convention of writing “primed” static variables, T ′ 0, ..., T ′ m, U ′ 0, ..., to stand for fresh static variables. Our procedure will introduce primed static variables as placeholders that are to be replaced with 153
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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
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40.10The Trait Fortress.Core.Binary
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Chapter 1 Introduction The Fortress
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A note on the presented libraries i
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component HelloWorld export Executa
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foo:String → () baz: String → S
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fortress upgrade Gary with Ralph No
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halve(x : R64) : R64 = x/2 Predicta
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while x < 10 do print x x += 1 end
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It is also possible to convert a me
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factorial(n) = ∏ i←1:n i This f
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In both methods cons and append , t
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default distributions will provide
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Chapter 3 Programs A program consis
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Chapter 10), a literal (see Section
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(discussed in Section 13.13) to a s
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Chapter 5 Lexical Structure A Fortr
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U+0021 EXCLAMATION MARK ! U+0023 NU
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If a character (or any other syntac
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BIG SI unit absorbs abstract also a
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escape sequences are useful for ASC
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5.14.1 Multicharacter Enclosing Ope
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Note: the elegant way to write Avog
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• top-level variable declarations
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declares id to be a mutable variabl
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several new variables. This syntax
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Chapter 7 Names Names are used to r
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7.3 Qualified Names Fortress provid
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Fortress also allows coercion betwe
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• element types of a tuple type c
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TypeAlias ::= type Id [StaticParams
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‘}’. If such a clause contains
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Note that a trait declaration inher
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the parametric trait WrappedDiction
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Chapter 10 Objects An object is a v
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FldDef ::= FldMod ∗ Id [IsType] (
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Chapter 11 Static Parameters Trait,
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11.5 Operator and Identifier Parame
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Chapter 12 Functions Functions are
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swap(x :Object, y : Object) = (y, x
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A function declaration may be separ
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Chapter 13 Expressions Fortress is
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Negating the literal 0 produces a s
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the function is evaluated with the
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13.10 Assignments Syntax: Expr ::=
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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
Page 111 and 112: 13.27.2 Static Expressions and Valu
Page 113 and 114: A = [1 2 3; 4 5 6; 7 8 9] then A 1,
Page 115 and 116: evaluates to the set {0, 4, 16} Map
Page 117 and 118: ignore(f x) is equivalent to: f x;
Page 119 and 120: trait CheckedException extends { Ex
Page 121 and 122: Chapter 15 Overloading and Multiple
Page 123 and 124: e called with. In other words, we e
Page 125 and 126: Chapter 16 Operators Operators are
Page 127 and 128: • “ordinary” operators: + −
Page 129 and 130: left context whitespace operator fi
Page 131 and 132: The rules below are designed to for
Page 133 and 134: 16.8.3 Enclosing Operators When use
Page 135 and 136: 16.8.9 Intersection, Union, and Set
Page 137 and 138: Chapter 17 Conversions and Coercion
Page 139 and 140: 17.3 Coercion Invocations One may i
Page 141 and 142: arguments nor with variable number
Page 143 and 144: trait B extends A end trait C exten
Page 145 and 146: a new coercion in a subexpression
Page 147 and 148: for tokens. For readability, plural
Page 149 and 150: Chapter 19 Tests and Properties For
Page 151: 19.5 Test Suites In order to allow
Page 155 and 156: 3. If a i is a functional applicati
Page 157 and 158: 21.2 Programming Discipline If Fort
Page 159 and 160: Here the call f(a, a) ends up setti
Page 161 and 162: 2. Ancestors, dynamically ordered b
Page 163 and 164: The ways in which fortresses are ac
Page 165 and 166: Component equivalence is determined
Page 167 and 168: 22.5 Type Inference for Components
Page 169 and 170: Fortress.IO Fortress.Crypto IronLin
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Page 173 and 174: 3. If the replacement does not expo
Page 175 and 176: This method runs all test functions
Page 177 and 178: Fortress.IO Fortress.Crypto Fortres
Page 179 and 180: Part III Fortress APIs and Document
Page 181 and 182: 23.1.3 hash(maxval: N64): N64 23.1.
Page 183 and 184: opr =(self,other: Boolean):Boolean
Page 185 and 186: 24.1.20 getter hashCode(): N64 24.1
Page 187 and 188: False: BooleanInterval Uncertain: B
Page 189 and 190: 24.2.11 opr ∧(self,other: Boolean
Page 191 and 192: 24.2.19 possibly(self): Boolean 24.
Page 193 and 194: Chapter 25 Numbers 25.1 Rational Nu
Page 195 and 196: opr ⌈self ⌉: N realpart(self):
Page 197 and 198: 25.1.11 opr (self,other: Q):Boolean
Page 199 and 200: 25.1.26 floor(self): Z 25.1.27 opr
Page 201 and 202: 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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