Change interface prefix from ? to ~

? will eventually be used in place of * to denote an optional
pointer, and ~ already means "approximation", which works well for
a polymorphic data structure.

entity/type.go

@@ -130,7 +130,7 @@ type TypeInterface struct {
 }
 func (*TypeInterface) ty(){}
 func (this *TypeInterface) String () string {
-	out := "(?"
+	out := "(~"
 	for _, behavior := range this.Behaviors {
 		out += fmt.Sprint(" ", behavior)
 	}

parser/parser_test.go

@@ -7,7 +7,7 @@ testString (test,
 // correct
 `- BasicInt: Int
 - Structure: (. x:Int y:Int)
-- Interface: (? [aMethod x:Int]:*U8 [otherMethod arg:5:Int]:*U8)
+- Interface: (~ [aMethod x:Int]:*U8 [otherMethod arg:5:Int]:*U8)
 - Array: 16:16:16:Int
 - StructArray: 31:24:340920:(. x:Int y:Int)
 - String: *:U8`,
@@ -17,7 +17,7 @@ BasicInt: Int
 Structure: (.
 	x:Int
 	y:Int)
-Interface: (?
+Interface: (~
 	[aMethod x:Int]:*U8
 	[otherMethod arg:5:Int]:*U8)
 Array: 16:16:16:Int

parser/type.go

@@ -57,12 +57,12 @@ func (this *Parser) parseType () (entity.Type, error) {
 	case lexer.LParen:
 		err := this.expectNext(lexer.Dot, lexer.Symbol)
 		if err != nil { return nil, err }
-		err = this.expectValue(0, ".", "?", "|")
+		err = this.expectValue(0, ".", "~", "|")
 		if err != nil { return nil, err }
 		
 		switch this.value() {
 		case ".": return this.parseTypeStructCore()
-		case "?": return this.parseTypeInterfaceCore()
+		case "~": return this.parseTypeInterfaceCore()
 		}
 		panic(this.bug())
 	}
@@ -155,7 +155,7 @@ func (this *Parser) parseTypeStructCore () (entity.Type, error) {
 }
 
 func (this *Parser) parseTypeInterfaceCore () (entity.Type, error) {
-	err := this.expectValue(lexer.Symbol, "?")
+	err := this.expectValue(lexer.Symbol, "~")
 	if err != nil { return nil, err }
 	ty := &entity.TypeInterface {
 		Position: this.pos(),