reflow/syntax: add range builtin

Summary:
Range allows the user to generate lists of indices, e.g.:

	range(1, 5) == [1,2,3,4]

Reviewers: pgopal, pknudsgaard

Reviewed By: pknudsgaard

Differential Revision: https://phabricator.grailbio.com/D10005

fbshipit-source-id: 6f5ec00

syntax/eval.go

@@ -23,6 +23,8 @@ import (
 var (
 	coerceExecOutputDigest = reflow.Digester.FromString("grail.com/reflow/syntax.Eval.coerceExecOutput")
 	sequenceDigest         = reflow.Digester.FromString("grail.com/reflow/syntax.Eval.~>")
+
+	one = big.NewInt(1)
 )
 
 // Eval evaluates the expression e and returns its value (or error).
@@ -637,6 +639,18 @@ func (e *Expr) eval(sess *Session, env *values.Env, ident string) (val values.T,
 				fmt.Fprintf(os.Stderr, "%s%s: %s\n", e.Position, ident, values.Sprint(vs[0], e.Left.Type))
 				return vs[0], nil
 			}, tval{e.Left.Type, left})
+		case "range":
+			return e.k(sess, env, ident, func(vs []values.T) (values.T, error) {
+				left, right := vs[0].(*big.Int), vs[1].(*big.Int)
+				if left.Cmp(right) > 0 {
+					return nil, errors.New("invalid range")
+				}
+				var list values.List
+				for i := new(big.Int).Set(left); i.Cmp(right) < 0; i.Add(i, one) {
+					list = append(list, new(big.Int).Set(i))
+				}
+				return list, nil
+			}, e.Left, e.Right)
 		}
 	case ExprRequires:
 		req, err := e.evalRequirements(sess, env, ident)

syntax/expr.go

@@ -752,6 +752,14 @@ func (e *Expr) init(sess *Session, env *types.Env) {
 			e.Type = e.Left.Type.Assign(nil)
 		case "trace":
 			e.Type = e.Left.Type.Assign(nil)
+		case "range":
+			if e.Left.Type.Kind != types.IntKind {
+				e.Type = types.Errorf("range expects an integer, not %s", e.Left.Type)
+			} else if e.Right.Type.Kind != types.IntKind {
+				e.Type = types.Errorf("range expects an integer, not %s", e.Right.Type)
+			} else {
+				e.Type = types.List(types.Int)
+			}
 		}
 	case ExprRequires:
 		if err := e.initResources(sess, env); err != nil {
@@ -1056,9 +1064,9 @@ func (e *Expr) String() string {
 var binopPrec = map[string]int{
 	"||": 2,
 	"&&": 3,
-	"<":  4, ">": 4, "<=": 4, ">=": 4, "!=": 4, "==": 4,
-	"+": 5, "-": 5, "|": 5, "^": 5,
-	"*": 6, "/": 6, "%": 6, "&": 6, "<<": 6, ">>": 6,
+	"<":  5, ">": 5, "<=": 5, ">=": 5, "!=": 5, "==": 5,
+	"+": 6, "-": 6, "|": 6, "^": 6,
+	"*": 7, "/": 7, "%": 7, "&": 7, "<<": 7, ">>": 7,
 }
 
 // Prec returns the precedence of expression e. If it is not a binary

syntax/parse.go

@@ -177,6 +177,8 @@ var identTokens = map[string]int{
 
 	"type": tokType,
 
+	"range": tokRange,
+
 	// Reserved identifiers:
 	"force":   tokReserved,
 	"switch":  tokReserved,

syntax/reflow.y

@@ -72,7 +72,7 @@ type typearg struct {
 %token	<pos>	tokVal tokFunc tokAssign tokArrow tokLeftArrow tokIf tokElse 
 %token	<pos>	tokMake tokLen  tokPanic tokDelay tokTrace tokMap tokList tokZip tokUnzip tokFlatten
 %token	<pos>	tokStartModule tokStartDecls tokStartExpr tokStartType
-%token	<pos>	tokKeyspace tokParam tokEllipsis  tokReserved  tokRequires
+%token	<pos>	tokKeyspace tokParam  tokEllipsis  tokReserved  tokRequires tokRange
 %token	<pos>	tokType
 %token	<pos>	'{' '(' '['
 %token	<pos>	tokOrOr tokAndAnd tokLE tokGE  tokNE tokEqEq tokLSH tokRSH
@@ -558,6 +558,8 @@ term:
 	{$$ = &Expr{Position: $1.Position, Comment: $1.comment, Kind: ExprBuiltin, Op: "flatten", Left: $3}}
 |	tokMap '(' expr ')'
 	{$$ = &Expr{Position: $1.Position, Comment: $1.comment, Kind: ExprBuiltin, Op: "map", Left: $3}}
+|	tokRange '(' expr ',' expr ')'
+	{$$ = &Expr{Position: $1.Position, Comment: $1.comment, Kind: ExprBuiltin, Op: "range", Left: $3, Right: $5}}
 |	tokList '(' expr ')'
 	{$$ = &Expr{Position: $1.Position, Comment: $1.comment, Kind: ExprBuiltin, Op: "list", Left: $3}}
 |	tokDelay '(' expr ')'

syntax/testdata/test1.rf

@@ -169,3 +169,8 @@ val TestCommaOks = {
 	)
 	true
 }
+
+val TestRange = {
+	func eq(x, y [int]) bool = test.All([x == y | (x, y) <- zip(x, y)])
+	eq(range(1, 2), [1]) && eq(range(0, 4), [0,1,2,3]) && len(range(0, 5000)) == 5000
+}