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value.go
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value.go
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package bytecode
import (
"fmt"
"strconv"
"strings"
"evylang.dev/evy/pkg/parser"
)
var (
// ErrBounds reports an index out of bounds in an array or string.
ErrBounds = fmt.Errorf("%w: index out of bounds", ErrPanic)
// ErrMapKey reports that no value was found for a specific key
// used in a map index.
ErrMapKey = fmt.Errorf("%w: no value for map key", ErrPanic)
// ErrSlice reports an invalid slice where start index > end index.
ErrSlice = fmt.Errorf("%w: invalid slice", ErrPanic)
)
type value interface {
Type() *parser.Type
Equals(value) bool
String() string
}
type indexable interface {
// Index returns the value at the specified key. A user error will
// be returned if the key is not found inside the structure.
Index(key value) (value, error)
}
type sliceable interface {
// Slice returns a subset of elements between the start (inclusive)
// and end (exclusive) index. A user error will be returned if start
// or end index are outside the bounds of the structure.
Slice(start, end value) (value, error)
}
type numVal float64
func (n numVal) Type() *parser.Type { return parser.NUM_TYPE }
func (n numVal) String() string {
return strconv.FormatFloat(float64(n), 'f', -1, 64)
}
func (n numVal) Equals(v value) bool {
n2, ok := v.(numVal)
if !ok {
panic("internal error: Num.Equals called with non-Num value")
}
return n == n2
}
type boolVal bool
func (boolVal) Type() *parser.Type { return parser.BOOL_TYPE }
func (b boolVal) String() string {
return strconv.FormatBool(bool(b))
}
func (b boolVal) Equals(v value) bool {
b2, ok := v.(boolVal)
if !ok {
panic("internal error: Bool.Equals called with non-Bool value")
}
return b == b2
}
type stringVal string
func (s stringVal) Type() *parser.Type { return parser.STRING_TYPE }
func (s stringVal) String() string {
return string(s)
}
func (s stringVal) Equals(v value) bool {
s2, ok := v.(stringVal)
if !ok {
panic("internal error: String.Equals called with non-String value")
}
return s == s2
}
func (s stringVal) Index(idx value) (value, error) {
index := int(idx.(numVal))
if index >= len(s) || index < -len(s) {
return nil, fmt.Errorf("%w: %d", ErrBounds, index)
}
if index < 0 {
index += len(s)
}
return s[index : index+1], nil
}
func (s stringVal) Slice(start, end value) (value, error) {
startIdx, endIdx, err := normalizeSliceIndices(start, end, len(s))
if err != nil {
return nil, err
}
return s[startIdx:endIdx], nil
}
type arrayVal struct {
Elements []value
}
func (a arrayVal) Type() *parser.Type {
// Revisit this when adding the typeof builtin: https://github.com/evylang/evy/pull/305#discussion_r1531149977
return parser.GENERIC_ARRAY
}
func (a arrayVal) String() string {
elements := make([]string, len(a.Elements))
for i, e := range a.Elements {
elements[i] = e.String()
}
return "[" + strings.Join(elements, " ") + "]"
}
func (a arrayVal) Equals(v value) bool {
a2, ok := v.(arrayVal)
if !ok {
panic("internal error: Array.Equals called with non-Array value")
}
if len(a.Elements) != len(a2.Elements) {
return false
}
elements2 := a2.Elements
for i, e := range a.Elements {
e2 := elements2[i]
if !e.Equals(e2) {
return false
}
}
return true
}
func (a arrayVal) Index(idx value) (value, error) {
index := int(idx.(numVal))
length := len(a.Elements)
if index >= length || index < -length {
return nil, fmt.Errorf("%w: %d", ErrBounds, index)
}
if index < 0 {
index += length
}
return a.Elements[index], nil
}
// Set checks that idx is in bounds and then sets
// the value of the element at idx to val.
func (a arrayVal) Set(idx, val value) error {
index := int(idx.(numVal))
length := len(a.Elements)
if index >= length || index < -length {
return fmt.Errorf("%w: %d", ErrBounds, index)
}
if index < 0 {
index += length
}
a.Elements[index] = val
return nil
}
func (a arrayVal) Slice(start, end value) (value, error) {
startIdx, endIdx, err := normalizeSliceIndices(start, end, len(a.Elements))
if err != nil {
return nil, err
}
elements := make([]value, endIdx-startIdx)
copy(elements, a.Elements[startIdx:endIdx])
return arrayVal{Elements: elements}, nil
}
type mapVal map[string]value
func (m mapVal) Type() *parser.Type {
return parser.GENERIC_MAP
}
func (m mapVal) String() string {
pairs := []string{}
for k, v := range m {
pairs = append(pairs, fmt.Sprintf("%s: %s", k, v.String()))
}
return "{" + strings.Join(pairs, ", ") + "}"
}
func (m mapVal) Equals(v value) bool {
m2, ok := v.(mapVal)
if !ok {
panic("internal error: Map.Equals called with non-Map value")
}
if len(m) != len(m2) {
return false
}
for key, val := range m {
val2 := m2[key]
if val2 == nil || !val.Equals(val2) {
return false
}
}
return true
}
func (m mapVal) Index(idx value) (value, error) {
k := idx.(stringVal)
key := string(k)
val, ok := m[key]
if !ok {
return nil, fmt.Errorf("%w %q", ErrMapKey, key)
}
return val, nil
}
type noneVal struct{}
func (noneVal) Type() *parser.Type {
return parser.NONE_TYPE
}
func (noneVal) String() string {
return ""
}
func (noneVal) Equals(_ value) bool {
return false
}
func normalizeSliceIndices(start, end value, length int) (int, int, error) {
startIdx := 0
if _, ok := start.(numVal); ok {
startIdx = int(start.(numVal))
}
if startIdx > length || startIdx < -length {
return 0, 0, fmt.Errorf("%w: %d", ErrBounds, start)
}
if startIdx < 0 {
startIdx += length
}
endIdx := length
if _, ok := end.(numVal); ok {
endIdx = int(end.(numVal))
}
if endIdx > length || endIdx < -length {
return 0, 0, fmt.Errorf("%w: %d", ErrBounds, end)
}
if endIdx < 0 {
endIdx += length
}
if startIdx > endIdx {
return 0, 0, fmt.Errorf("%w: start (%d) > end (%d)", ErrSlice,
startIdx, endIdx)
}
return startIdx, endIdx, nil
}