Add back 0-based indexes (#6348)

This commit adds back 0-based index/slice expressions to the language.
It also institutes pragmas declarations that allow users to specify
1-based or 0-based indexes for a given scope.

Author: mattnibs

book/src/super-sql/functions/records/unflatten.md

@@ -37,7 +37,7 @@ _Flatten to unflatten_
 ```mdtest-spq
 # spq
 unnest flatten(this) into (
-  key[1] != "rm"
+  key[0] != "rm"
   | values collect(this)
 )
 | values unflatten(this)

book/src/super-sql/functions/strings/upper.md

@@ -31,7 +31,7 @@ values upper(this)
 ```mdtest-spq
 # spq
 fn capitalize(str): (
-  upper(str[1:2]) + str[2:]
+  upper(str[0:1]) + str[1:]
 )
 values capitalize(this)
 # input

book/src/super-sql/operators/unnest.md

@@ -184,7 +184,7 @@ unnest {s,a} into ( sum(a) by s )
 _Unnested the elements of a record by flattening it_
 ```mdtest-spq
 # spq
-unnest {s,f:flatten(r)} into ( values {s,key:f.key[1],val:f.value} )
+unnest {s,f:flatten(r)} into ( values {s,key:f.key[0],val:f.value} )
 # input
 {s:"foo",r:{a:1,b:2}}
 {s:"bar",r:{a:3,b:4}}

compiler/ast/decl.go

@@ -27,6 +27,13 @@ type OpDecl struct {
 	Loc    `json:"loc"`
 }
 
+type PragmaDecl struct {
+	Kind string `json:"kind" unpack:""`
+	Name *ID    `json:"name"`
+	Expr Expr   `json:"expr"`
+	Loc  `json:"loc"`
+}
+
 type QueryDecl struct {
 	Kind string `json:"kind" unpack:""`
 	Name *ID    `json:"name"`
@@ -41,8 +48,9 @@ type TypeDecl struct {
 	Loc  `json:"loc"`
 }
 
-func (*ConstDecl) declNode() {}
-func (*FuncDecl) declNode()  {}
-func (*OpDecl) declNode()    {}
-func (*QueryDecl) declNode() {}
-func (*TypeDecl) declNode()  {}
+func (*ConstDecl) declNode()  {}
+func (*FuncDecl) declNode()   {}
+func (*OpDecl) declNode()     {}
+func (*PragmaDecl) declNode() {}
+func (*QueryDecl) declNode()  {}
+func (*TypeDecl) declNode()   {}

compiler/ast/unpack.go

@@ -65,6 +65,7 @@ var unpacker = unpack.New(
 	OpDecl{},
 	OutputOp{},
 	PassOp{},
+	PragmaDecl{},
 	Primitive{},
 	PutOp{},
 	Record{},

compiler/dag/expr.go

@@ -69,6 +69,7 @@ type (
 		Kind  string `json:"kind" unpack:""`
 		Expr  Expr   `json:"expr"`
 		Index Expr   `json:"index"`
+		Base1 bool   `json:"base1"`
 	}
 	IsNullExpr struct {
 		Kind string `json:"kind" unpack:""`
@@ -112,10 +113,11 @@ type (
 		Elems []VectorElem `json:"elems"`
 	}
 	SliceExpr struct {
-		Kind string `json:"kind" unpack:""`
-		Expr Expr   `json:"expr"`
-		From Expr   `json:"from"`
-		To   Expr   `json:"to"`
+		Kind  string `json:"kind" unpack:""`
+		Expr  Expr   `json:"expr"`
+		From  Expr   `json:"from"`
+		To    Expr   `json:"to"`
+		Base1 bool   `json:"base1"`
 	}
 	SortExpr struct {
 		Key   Expr        `json:"key"`