Array length

docs/usage/expressions.md

@@ -324,6 +324,14 @@ Syntax: `{@ ele0 ele1 ele2}` (`{$ ele0 ele1 ele2}` is equivalent)
 
 Creates an array with the provided elements. Use `{@}` for an array of all matches.
 
+#### @len
+
+Syntax: `{@len array}`
+
+Returns the length of an array.  Empty "" returns 0, a literal will be 1.
+
+**Note:** This is a linear-time operation.
+
 #### @in
 
 Syntax: `{@in <val> array}` or `{@in <val> {@ val0 val1 val2 ...}}`

pkg/expressions/stdlib/funcs.go

@@ -82,6 +82,7 @@ var StandardFunctions = map[string]KeyBuilderFunction{
 
 	// Ranges
 	"@":       kfJoin(ArraySeparator),
+	"@len":    kfArrayLen,
 	"@map":    kfArrayMap,
 	"@split":  kfArraySplit,
 	"@select": kfArraySelect,

pkg/expressions/stdlib/funcsRange.go

@@ -4,6 +4,7 @@ import (
 	. "rare/pkg/expressions" //lint:ignore ST1001 Legacy
 	"rare/pkg/slicepool"
 	"rare/pkg/stringSplitter"
+	"strconv"
 	"strings"
 )
 
@@ -34,6 +35,22 @@ func (s *subContext) Eval(stage KeyBuilderStage, v0, v1 string) string {
 	return stage(s)
 }
 
+// {@len <arr>}
+func kfArrayLen(args []KeyBuilderStage) (KeyBuilderStage, error) {
+	if len(args) != 1 {
+		return stageErrArgCount(args, 1)
+	}
+	return func(context KeyBuilderContext) string {
+		val := args[0](context)
+		if val == "" {
+			return "0"
+		}
+
+		count := strings.Count(val, ArraySeparatorString) + 1
+		return strconv.Itoa(count)
+	}, nil
+}
+
 // {@split <string> "delim"}
 func kfArraySplit(args []KeyBuilderStage) (KeyBuilderStage, error) {
 	if !isArgCountBetween(args, 1, 2) {

pkg/expressions/stdlib/funcsRange_test.go

@@ -11,6 +11,13 @@ func TestArray(t *testing.T) {
 	testExpression(t, mockContext("q"), "{$ {0}}", "q")
 }
 
+func TestArrayLen(t *testing.T) {
+	testExpression(t, mockContext("abc"), "{@len {0}}", "1")
+	testExpression(t, mockContext(expressions.MakeArray("a", "bc", "c")), "{@len {0}}", "3")
+	testExpression(t, mockContext(""), "{@len {0}}", "0")
+	testExpressionErr(t, mockContext(), "{@len a b}", "<ARGN>", ErrArgCount)
+}
+
 func TestArraySplit(t *testing.T) {
 	testExpression(
 		t,