Added additional builtins for strings and lists

Co-authored-by: Leon Mika <lmika@lmika.com>
Reviewed-on: #2

.forgejo/workflows/build.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v2
         with:
-          go-version: 1.24
+          go-version: 1.25
       - uses: actions/setup-node@v4
         with:
           node-version: 21.1

.forgejo/workflows/test.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v2
         with:
-          go-version: 1.22.4
+          go-version: 1.25
       - name: Build
         run: |
           make test

go.mod

@@ -1,21 +1,20 @@
 module ucl.lmika.dev
 
-go 1.24
+go 1.25
 
 require (
 	github.com/alecthomas/participle/v2 v2.1.1
 	github.com/chzyer/readline v1.5.1
-	github.com/lmika/gopkgs v0.0.0-20240408110817-a02f6fc67d1f
 	github.com/stretchr/testify v1.10.0
-	lmika.dev/pkg/modash v0.0.0-20250619112300-0be0b6b35b1b
+	github.com/yuin/goldmark v1.7.8
+	go.abhg.dev/goldmark/frontmatter v0.2.0
+	lmika.dev/pkg/modash v0.1.0
 )
 
 require (
 	github.com/BurntSushi/toml v1.2.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/yuin/goldmark v1.7.8 // indirect
-	go.abhg.dev/goldmark/frontmatter v0.2.0 // indirect
 	golang.org/x/sys v0.0.0-20220310020820-b874c991c1a5 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -16,24 +16,19 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
 github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
-github.com/lmika/gopkgs v0.0.0-20240408110817-a02f6fc67d1f h1:tz68Lhc1oR15HVz69IGbtdukdH0x70kBDEvvj5pTXyE=
-github.com/lmika/gopkgs v0.0.0-20240408110817-a02f6fc67d1f/go.mod h1:zHQvhjGXRro/Xp2C9dbC+ZUpE0gL4GYW75x1lk7hwzI=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/yuin/goldmark v1.7.8 h1:iERMLn0/QJeHFhxSt3p6PeN9mGnvIKSpG9YYorDMnic=
 github.com/yuin/goldmark v1.7.8/go.mod h1:uzxRWxtg69N339t3louHJ7+O03ezfj6PlliRlaOzY1E=
 go.abhg.dev/goldmark/frontmatter v0.2.0 h1:P8kPG0YkL12+aYk2yU3xHv4tcXzeVnN+gU0tJ5JnxRw=
 go.abhg.dev/goldmark/frontmatter v0.2.0/go.mod h1:XqrEkZuM57djk7zrlRUB02x8I5J0px76YjkOzhB4YlU=
+golang.org/x/sys v0.0.0-20220310020820-b874c991c1a5 h1:y/woIyUBFbpQGKS0u1aHF/40WUDnek3fPOyD08H5Vng=
 golang.org/x/sys v0.0.0-20220310020820-b874c991c1a5/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
-golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-lmika.dev/pkg/modash v0.0.0-20250619112300-0be0b6b35b1b h1:Oymcj66pgyJ2CtGk9lPh06P4FOekllE1iPehDwaL0vw=
+lmika.dev/pkg/modash v0.1.0 h1:fltroSvP0nKj9K0E6G+S9LULvB9Qhj47+SZ2b9v/v/c=
-lmika.dev/pkg/modash v0.0.0-20250619112300-0be0b6b35b1b/go.mod h1:8NDl/yR1eCCEhip9FJlVuMNXIeaztQ0Ks/tizExFcTI=
+lmika.dev/pkg/modash v0.1.0/go.mod h1:8NDl/yR1eCCEhip9FJlVuMNXIeaztQ0Ks/tizExFcTI=

repl/docs.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"github.com/lmika/gopkgs/fp/maps"
+	"lmika.dev/pkg/modash/momap"
 	"os"
 	"slices"
 	"sort"
@@ -33,7 +33,7 @@ func (d Doc) config(cmdName string, r *REPL) {
 func (r *REPL) helpBuiltin(ctx context.Context, args ucl.CallArgs) (any, error) {
 	switch {
 	case args.NArgs() == 0:
-		names := maps.Keys(r.commandDocs)
+		names := momap.Keys(r.commandDocs)
 		sort.Strings(names)
 
 		tabWriter := tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ', 0)

ucl/builtins/fns_test.go

@@ -0,0 +1,31 @@
+package builtins_test
+
+import (
+	"context"
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"ucl.lmika.dev/ucl"
+	"ucl.lmika.dev/ucl/builtins"
+)
+
+func TestFns_Uni(t *testing.T) {
+	tests := []struct {
+		descr string
+		eval  string
+		want  any
+	}{
+		{descr: "uni 1", eval: `s = fns:uni add 2 ; $s 3`, want: 5},
+		{descr: "uni 2", eval: `s = fns:uni (proc { |x| add $x 1 }) ; $s 3`, want: 4},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.descr, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Fns()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, res)
+		})
+	}
+}

ucl/builtins/lists.go

@@ -3,6 +3,7 @@ package builtins
 import (
 	"context"
 	"errors"
+
 	"ucl.lmika.dev/ucl"
 )
 
@@ -10,12 +11,46 @@ func Lists() ucl.Module {
 	return ucl.Module{
 		Name: "lists",
 		Builtins: map[string]ucl.BuiltinHandler{
-			"first": listFirst,
+			"append":  listAppend,
-			"uniq":  listUniq,
+			"first":   listFirst,
+			"batch":   listBatch,
+			"uniq":    listUniq,
+			"sublist": listSublist,
 		},
 	}
 }
 
+func listAppend(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		what ucl.Object
+		item ucl.Object
+	)
+
+	if err := args.Bind(&what); err != nil {
+		return nil, err
+	}
+
+	if what == nil {
+		what = ucl.NewListObject()
+	}
+
+	t, ok := what.(ucl.ModListable)
+	if !ok {
+		return nil, errors.New("expected mutable list")
+	}
+
+	for args.NArgs() > 0 {
+		if err := args.Bind(&item); err != nil {
+			return nil, err
+		}
+		if err := t.Insert(-1, item); err != nil {
+			return nil, err
+		}
+	}
+
+	return t, nil
+}
+
 func listFirst(ctx context.Context, args ucl.CallArgs) (any, error) {
 	var (
 		what  ucl.Object
@@ -125,3 +160,83 @@ func listUniq(ctx context.Context, args ucl.CallArgs) (any, error) {
 
 	return found, nil
 }
+
+func listBatch(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		what      ucl.Object
+		groupSize int
+	)
+
+	if err := args.Bind(&what, &groupSize); err != nil {
+		return nil, err
+	}
+
+	if groupSize <= 0 {
+		return nil, errors.New("group size must be > 0")
+	}
+
+	groups := ucl.NewListObject()
+	var thisGroup *ucl.ListObject
+
+	if err := eachListOrIterItem(ctx, what, func(idx int, v ucl.Object) error {
+		if thisGroup == nil || thisGroup.Len() == groupSize {
+			thisGroup = ucl.NewListObject()
+			groups.Append(thisGroup)
+		}
+		thisGroup.Append(v)
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	return groups, nil
+}
+
+func listSublist(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		l             ucl.Listable
+		from, fromIdx int
+		to, toIdx     int
+	)
+
+	if err := args.Bind(&l, &from); err != nil {
+		return nil, err
+	}
+
+	if l == nil {
+		return nil, nil
+	}
+
+	if args.NArgs() >= 1 {
+		if err := args.Bind(&to); err != nil {
+			return nil, err
+		}
+
+		fromIdx, toIdx = listPos(l, from), listPos(l, to)
+	} else {
+		if from < 0 {
+			fromIdx, toIdx = listPos(l, from), l.Len()
+		} else {
+			fromIdx, toIdx = 0, listPos(l, from)
+		}
+	}
+
+	if fromIdx > toIdx {
+		return ucl.NewListObject(), nil
+	}
+
+	newList := ucl.NewListObjectOfLength(toIdx - fromIdx)
+	for i := fromIdx; i < toIdx; i++ {
+		if err := newList.SetIndex(i-fromIdx, l.Index(i)); err != nil {
+			return nil, err
+		}
+	}
+	return newList, nil
+}
+
+func listPos(l ucl.Listable, pos int) int {
+	if pos < 0 {
+		return max(l.Len()+pos, 0)
+	}
+	return min(pos, l.Len())
+}

ucl/builtins/lists_test.go

@@ -2,12 +2,51 @@ package builtins_test
 
 import (
 	"context"
-	"github.com/stretchr/testify/assert"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 	"ucl.lmika.dev/ucl"
 	"ucl.lmika.dev/ucl/builtins"
 )
 
+func TestLists_Append(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "append 1", eval: `lists:append [1 2 3] 4`, want: []any{1, 2, 3, 4}},
+		{desc: "append 2", eval: `lists:append [1 2 3] 4 5 6`, want: []any{1, 2, 3, 4, 5, 6}},
+		{desc: "append 3", eval: `lists:append [] 1 2 3`, want: []any{1, 2, 3}},
+		{desc: "append 4", eval: `lists:append () 1 2 3`, want: []any{1, 2, 3}},
+		{desc: "append 5", eval: `lists:append [1 2 3]`, want: []any{1, 2, 3}},
+		{desc: "append 6", eval: `l = [] ; lists:append $l 1 2 3 ; $l`, want: []any{1, 2, 3}},
+		{desc: "append 7", eval: `l = [1 2 3] ; lists:append $l [4 5 6] ; $l`, want: []any{1, 2, 3, []any{4, 5, 6}}},
+		{desc: "append 8", eval: `lists:append (seq 3 | itrs:from | itrs:to-list) 4 5 6`, want: []any{0, 1, 2, 4, 5, 6}},
+
+		{desc: "err 1", eval: `lists:append "asa" 1`, wantErr: true},
+		{desc: "err 2", eval: `lists:append 123 1`, wantErr: true},
+		{desc: "err 3", eval: `lists:append [:] 1`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Itrs()),
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
 func TestLists_First(t *testing.T) {
 	tests := []struct {
 		desc    string
@@ -45,6 +84,42 @@ func TestLists_First(t *testing.T) {
 	}
 }
 
+func TestLists_Batch(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "batch 1", eval: `lists:batch [1 2 3 4 5] 2`, want: []any{[]any{1, 2}, []any{3, 4}, []any{5}}},
+		{desc: "batch 2", eval: `lists:batch [1 2 3 4] 2`, want: []any{[]any{1, 2}, []any{3, 4}}},
+		{desc: "batch 3", eval: `lists:batch [1 2 3 4 5] 3`, want: []any{[]any{1, 2, 3}, []any{4, 5}}},
+		{desc: "batch 4", eval: `lists:batch [1 2 3 4 5] 12`, want: []any{[]any{1, 2, 3, 4, 5}}},
+		{desc: "batch 5", eval: `lists:batch [1 2 3 4 5] 1`, want: []any{[]any{1}, []any{2}, []any{3}, []any{4}, []any{5}}},
+		{desc: "batch 6", eval: `lists:batch [1] 12`, want: []any{[]any{1}}},
+		{desc: "batch 7", eval: `lists:batch [] 12`, want: []any{}},
+
+		{desc: "err 1", eval: `lists:batch [1 2 3] -3`, wantErr: true},
+		{desc: "err 2", eval: `lists:batch [1 2 3] 0`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Itrs()),
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
 func TestLists_Uniq(t *testing.T) {
 	tests := []struct {
 		desc    string
@@ -76,6 +151,47 @@ func TestLists_Uniq(t *testing.T) {
 	}
 }
 
+func TestStrs_Sublist(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "sublist 1", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 5`, want: []any{"h", "e", "l", "l", "o"}},
+		{desc: "sublist 2", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 5000`, want: []any{"h", "e", "l", "l", "o", ",", " ", "w", "o", "r", "l", "d"}},
+		{desc: "sublist 3", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] -5`, want: []any{"w", "o", "r", "l", "d"}},
+		{desc: "sublist 4", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] -5000`, want: []any{"h", "e", "l", "l", "o", ",", " ", "w", "o", "r", "l", "d"}},
+		{desc: "sublist 5", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 0 5`, want: []any{"h", "e", "l", "l", "o"}},
+		{desc: "sublist 6", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 3 10`, want: []any{"l", "o", ",", " ", "w", "o", "r"}},
+		{desc: "sublist 7", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 3 10000`, want: []any{"l", "o", ",", " ", "w", "o", "r", "l", "d"}},
+		{desc: "sublist 8", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 3 -5`, want: []any{"l", "o", ",", " "}},
+		{desc: "sublist 9", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] -9 -5`, want: []any{"l", "o", ",", " "}},
+		{desc: "sublist 10", eval: `lists:sublist [h e l l o ',' ' ' w o r l d] 8 5`, want: []any{}},
+		{desc: "sublist 11", eval: `lists:sublist [] 8 5`, want: []any{}},
+
+		{desc: "err 1", eval: `lists:sublist`, wantErr: true},
+		{desc: "err 2", eval: `lists:sublist "asd"`, wantErr: true},
+		{desc: "err 3", eval: `lists:sublist ["asd"]`, wantErr: true},
+		{desc: "err 4", eval: `lists:sublist () 8 5`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
 func uclListOf(args ...any) *ucl.ListObject {
 	newList := ucl.NewListObject()
 	for _, arg := range args {

ucl/builtins/os.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"os"
 	"os/exec"
+	"strings"
 
 	"ucl.lmika.dev/ucl"
 )
@@ -72,6 +73,14 @@ func (oh osHandlers) exec(ctx context.Context, args ucl.CallArgs) (any, error) {
 		return nil, err
 	}
 
+	if args.HasSwitch("in") {
+		var inVal string
+		if err := args.BindSwitch("in", &inVal); err != nil {
+			return nil, err
+		}
+		cmd.Stdin = strings.NewReader(inVal)
+	}
+
 	res, err := cmd.Output()
 	if err != nil {
 		return nil, err

ucl/builtins/os_test.go

@@ -44,7 +44,8 @@ func TestOS_Exec(t *testing.T) {
 		want  any
 	}{
 		{descr: "run command 1", eval: `os:exec "echo" "hello, world"`, want: "hello, world\n"},
-		{descr: "run command 1", eval: `os:exec "date" "+%Y%m%d"`, want: time.Now().Format("20060102") + "\n"},
+		{descr: "run command 2", eval: `os:exec "date" "+%Y%m%d"`, want: time.Now().Format("20060102") + "\n"},
+		{descr: "run command 3", eval: `os:exec "tr" "[a-z]" "[A-Z]" -in "hello"`, want: "HELLO"},
 	}
 
 	for _, tt := range tests {

ucl/builtins/strs.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"strings"
+
 	"ucl.lmika.dev/ucl"
 )
 
@@ -11,16 +12,74 @@ func Strs() ucl.Module {
 	return ucl.Module{
 		Name: "strs",
 		Builtins: map[string]ucl.BuiltinHandler{
-			"to-upper":   toUpper,
+			"to-upper":    toUpper,
-			"to-lower":   toLower,
+			"to-lower":    toLower,
-			"trim":       trim,
+			"trim":        trim,
-			"split":      split,
+			"split":       split,
-			"join":       join,
+			"join":        join,
-			"has-prefix": hasPrefix,
+			"has-prefix":  hasPrefix,
+			"has-suffix":  hasSuffix,
+			"trim-prefix": trimPrefix,
+			"trim-suffix": trimSuffix,
+			"substr":      strsSubstr,
+			"replace":     strsReplace,
 		},
 	}
 }
 
+func strsReplace(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		s    string
+		from string
+		to   string
+	)
+
+	if err := args.Bind(&s, &from, &to); err != nil {
+		return nil, err
+	}
+
+	var count = -1
+	if args.HasSwitch("n") {
+		if err := args.BindSwitch("n", &count); err != nil {
+			return nil, err
+		}
+	}
+
+	return strings.Replace(s, from, to, count), nil
+}
+
+func strsSubstr(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		s    string
+		from int
+		to   int
+	)
+
+	if err := args.Bind(&s, &from); err != nil {
+		return nil, err
+	}
+
+	if args.NArgs() >= 1 {
+		if err := args.Bind(&to); err != nil {
+			return nil, err
+		}
+
+		ffr := strPos(s, from)
+		tfr := strPos(s, to)
+		if ffr > tfr {
+			return "", nil
+		}
+		return s[ffr:tfr], nil
+
+	} else {
+		if from < 0 {
+			return s[strPos(s, from):], nil
+		} else {
+			return s[:strPos(s, from)], nil
+		}
+	}
+}
+
 func toUpper(ctx context.Context, args ucl.CallArgs) (any, error) {
 	var s string
 	if err := args.Bind(&s); err != nil {
@@ -57,17 +116,40 @@ func hasPrefix(ctx context.Context, args ucl.CallArgs) (any, error) {
 	return strings.HasPrefix(s, prefix), nil
 }
 
-func split(ctx context.Context, args ucl.CallArgs) (any, error) {
+func hasSuffix(ctx context.Context, args ucl.CallArgs) (any, error) {
-	var s string
+	var s, suffix string
-	if err := args.Bind(&s); err != nil {
+	if err := args.Bind(&s, &suffix); err != nil {
 		return nil, err
 	}
 
-	sep := ""
+	return strings.HasSuffix(s, suffix), nil
-	if args.NArgs() > 0 {
+}
-		if err := args.Bind(&sep); err != nil {
+
-			return nil, err
+func trimPrefix(ctx context.Context, args ucl.CallArgs) (any, error) {
-		}
+	var s, prefix string
+	if err := args.Bind(&s, &prefix); err != nil {
+		return nil, err
+	}
+
+	return strings.TrimPrefix(s, prefix), nil
+}
+
+func trimSuffix(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var s, suffix string
+	if err := args.Bind(&s, &suffix); err != nil {
+		return nil, err
+	}
+
+	return strings.TrimSuffix(s, suffix), nil
+}
+
+func split(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var (
+		s   string
+		sep string
+	)
+	if err := args.Bind(&s, &sep); err != nil {
+		return nil, err
 	}
 
 	n := -1
@@ -128,3 +210,10 @@ func join(ctx context.Context, args ucl.CallArgs) (any, error) {
 
 	return nil, errors.New("expected listable or iterable as arg 1")
 }
+
+func strPos(s string, pos int) int {
+	if pos < 0 {
+		return max(len(s)+pos, 0)
+	}
+	return min(pos, len(s))
+}

ucl/builtins/strs_test.go

@@ -2,8 +2,9 @@ package builtins_test
 
 import (
 	"context"
-	"github.com/stretchr/testify/assert"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 	"ucl.lmika.dev/ucl"
 	"ucl.lmika.dev/ucl/builtins"
 )
@@ -145,14 +146,15 @@ func TestStrs_Split(t *testing.T) {
 		{desc: "split 3", eval: `strs:split "" ";"`, want: []string{""}},
 		{desc: "split 4", eval: `strs:split " " ";"`, want: []string{" "}},
 
-		{desc: "split by char 1", eval: `strs:split "123"`, want: []string{"1", "2", "3"}},
+		{desc: "split by char 1", eval: `strs:split "123" ""`, want: []string{"1", "2", "3"}},
 
 		{desc: "split max 1", eval: `strs:split "1,2,3" "," -max 2`, want: []string{"1", "2,3"}},
 		{desc: "split max 2", eval: `strs:split "1,2,3" "," -max 5`, want: []string{"1", "2", "3"}},
 
-		{desc: "split by char max 1", eval: `strs:split "12345" -max 3`, want: []string{"1", "2", "345"}},
+		{desc: "split by char max 1", eval: `strs:split "12345" "" -max 3`, want: []string{"1", "2", "345"}},
 
 		{desc: "err 1", eval: `strs:split "1,2,3" -max []`, wantErr: true},
+		{desc: "err 1", eval: `strs:split "1,2,3"`, wantErr: true},
 	}
 
 	for _, tt := range tests {
@@ -202,3 +204,184 @@ func TestStrs_Join(t *testing.T) {
 		})
 	}
 }
+
+func TestStrs_HasSuffix(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "has suffix 1", eval: `strs:has-suffix "hello, world" "world"`, want: true},
+		{desc: "has suffix 2", eval: `strs:has-suffix "hello, world" "hello"`, want: false},
+		{desc: "has suffix 3", eval: `strs:has-suffix "" "world"`, want: false},
+		{desc: "has suffix 4", eval: `strs:has-suffix "hello" ""`, want: true},
+		{desc: "has suffix 5", eval: `strs:has-suffix "test.txt" ".txt"`, want: true},
+		{desc: "has suffix 6", eval: `strs:has-suffix "test.txt" ".pdf"`, want: false},
+
+		{desc: "err 1", eval: `strs:has-suffix`, wantErr: true},
+		{desc: "err 2", eval: `strs:has-suffix "asd"`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
+func TestStrs_TrimPrefix(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "trim prefix 1", eval: `strs:trim-prefix "hello, world" "hello, "`, want: "world"},
+		{desc: "trim prefix 2", eval: `strs:trim-prefix "goodbye, world" "hello"`, want: "goodbye, world"},
+		{desc: "trim prefix 3", eval: `strs:trim-prefix "" "world"`, want: ""},
+		{desc: "trim prefix 4", eval: `strs:trim-prefix "hello" ""`, want: "hello"},
+		{desc: "trim prefix 5", eval: `strs:trim-prefix "test.txt" "test"`, want: ".txt"},
+		{desc: "trim prefix 6", eval: `strs:trim-prefix "/path/to/file" "/path/"`, want: "to/file"},
+
+		{desc: "err 1", eval: `strs:trim-prefix`, wantErr: true},
+		{desc: "err 2", eval: `strs:trim-prefix "asd"`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
+func TestStrs_TrimSuffix(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "trim suffix 1", eval: `strs:trim-suffix "hello, world" ", world"`, want: "hello"},
+		{desc: "trim suffix 2", eval: `strs:trim-suffix "hello, world" "goodbye"`, want: "hello, world"},
+		{desc: "trim suffix 3", eval: `strs:trim-suffix "" "world"`, want: ""},
+		{desc: "trim suffix 4", eval: `strs:trim-suffix "hello" ""`, want: "hello"},
+		{desc: "trim suffix 5", eval: `strs:trim-suffix "test.txt" ".txt"`, want: "test"},
+		{desc: "trim suffix 6", eval: `strs:trim-suffix "file.backup" ".backup"`, want: "file"},
+
+		{desc: "err 1", eval: `strs:trim-suffix`, wantErr: true},
+		{desc: "err 2", eval: `strs:trim-suffix "asd"`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
+func TestStrs_Substr(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "substr 1", eval: `strs:substr "hello, world" 5`, want: "hello"},
+		{desc: "substr 2", eval: `strs:substr "hello, world" 5000`, want: "hello, world"},
+		{desc: "substr 3", eval: `strs:substr "hello, world" -5`, want: "world"},
+		{desc: "substr 4", eval: `strs:substr "hello, world" -5000`, want: "hello, world"},
+		{desc: "substr 5", eval: `strs:substr "hello, world" 0 5`, want: "hello"},
+		{desc: "substr 6", eval: `strs:substr "hello, world" 3 10`, want: "lo, wor"},
+		{desc: "substr 7", eval: `strs:substr "hello, world" 3 10000`, want: "lo, world"},
+		{desc: "substr 8", eval: `strs:substr "hello, world" 3 -5`, want: "lo, "},
+		{desc: "substr 9", eval: `strs:substr "hello, world" -9 -5`, want: "lo, "},
+		{desc: "substr 10", eval: `strs:substr "hello, world" 8 5`, want: ""},
+		{desc: "substr 11", eval: `strs:substr "" 8 5`, want: ""},
+		{desc: "substr 12", eval: `strs:substr () 8 5`, want: ""},
+
+		{desc: "err 1", eval: `strs:substr`, wantErr: true},
+		{desc: "err 2", eval: `strs:substr "asd"`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
+
+func TestStrs_Replace(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "replace 1", eval: `strs:replace "hello hello hello" "hello" "world"`, want: "world world world"},
+		{desc: "replace 2", eval: `strs:replace "hello hi hello hi" "hello" "lo"`, want: "lo hi lo hi"},
+		{desc: "replace 3", eval: `strs:replace "hello hello hello" "hello" "world" -n 1`, want: "world hello hello"},
+		{desc: "replace 4", eval: `strs:replace "hello hello hello" "hello" "world" -n 2`, want: "world world hello"},
+		{desc: "replace 5", eval: `strs:replace "hello hello hello" "hello" "world" -n 0`, want: "hello hello hello"},
+		{desc: "replace 6", eval: `strs:replace "each one" "" "|"`, want: "|e|a|c|h| |o|n|e|"},
+		{desc: "replace 7", eval: `strs:replace "hello hello hello" "hello" ""`, want: "  "},
+		{desc: "replace 8", eval: `strs:replace "nothing to replace here" "what" "why"`, want: "nothing to replace here"},
+		{desc: "replace 9", eval: `strs:replace "" "what" "why"`, want: ""},
+		{desc: "replace 10", eval: `strs:replace "" "hello" "world" -n 0`, want: ""},
+
+		{desc: "err 1", eval: `strs:replace`, wantErr: true},
+		{desc: "err 2", eval: `strs:replace "asd"`, wantErr: true},
+		{desc: "err 3", eval: `strs:replace "asd" "asd"`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Strs()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}

ucl/inst.go

@@ -82,6 +82,7 @@ func New(opts ...InstOption) *Inst {
 	rootEC.addCmd("str", invokableFunc(strBuiltin))
 	rootEC.addCmd("int", invokableFunc(intBuiltin))
 
+	rootEC.addCmd("nil?", invokableFunc(notNilBuiltin))
 	rootEC.addCmd("!nil", invokableFunc(notNilBuiltin))
 
 	rootEC.addCmd("add", invokableFunc(addBuiltin))

ucl/objs.go

@@ -10,7 +10,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/lmika/gopkgs/fp/slices"
+	"lmika.dev/pkg/modash/moslice"
 )
 
 type Object interface {
@@ -62,6 +62,11 @@ func NewListObject() *ListObject {
 	return &ListObject{}
 }
 
+func NewListObjectOfLength(l int) *ListObject {
+	o := make(ListObject, l)
+	return &o
+}
+
 func (lo *ListObject) Append(o Object) {
 	*lo = append(*lo, o)
 }
@@ -626,7 +631,7 @@ func newStructProxyObject(v reflect.Value, orig reflect.Value) structProxyObject
 	return structProxyObject{
 		v:    v,
 		orig: orig,
-		vf:   slices.Filter(reflect.VisibleFields(v.Type()), func(t reflect.StructField) bool { return t.IsExported() }),
+		vf:   moslice.Filter(reflect.VisibleFields(v.Type()), func(t reflect.StructField) bool { return t.IsExported() }),
 	}
 }
 

ucl/userbuiltin.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 	"reflect"
 
-	"github.com/lmika/gopkgs/fp/slices"
+	"lmika.dev/pkg/modash/moslice"
 )
 
 type BuiltinHandler func(ctx context.Context, args CallArgs) (any, error)
@@ -291,7 +291,7 @@ func (i Invokable) Invoke(ctx context.Context, args ...any) (any, error) {
 		inst: i.inst,
 	}
 
-	invArgs.args, err = slices.MapWithError(args, func(a any) (Object, error) {
+	invArgs.args, err = moslice.MapWithError(args, func(a any) (Object, error) {
 		return fromGoValue(a)
 	})
 	if err != nil {