elvish/pkg/eval/vals/repr.go
2021-12-31 21:13:41 +00:00

96 lines
2.7 KiB
Go

package vals
import (
"fmt"
"math"
"math/big"
"reflect"
"strconv"
"src.elv.sh/pkg/parse"
)
// Reprer wraps the Repr method.
type Reprer interface {
// Repr returns a string that represents a Value. The string either be a
// literal of that Value that is preferably deep-equal to it (like `[a b c]`
// for a list), or a string enclosed in "<>" containing the kind and
// identity of the Value(like `<fn 0xdeadcafe>`).
//
// If indent is at least 0, it should be pretty-printed with the current
// indentation level of indent; the indent of the first line has already
// been written and shall not be written in Repr. The returned string
// should never contain a trailing newline.
Repr(indent int) string
}
// ReprPlain is like Repr, but without pretty-printing.
func ReprPlain(v interface{}) string {
// TODO: Change to math.MinInt when Go 1.17 is required.
return Repr(v, math.MinInt32)
}
// Repr returns the representation for a value, a string that is preferably
// (but not necessarily) an Elvish expression that evaluates to the argument.
// The representation is pretty-printed, using indent as the initial level of
// indentation. It is implemented for the builtin types nil, bool and string,
// the File, List and Map types, StructMap types, and types satisfying the
// Reprer interface. For other types, it uses fmt.Sprint with the format
// "<unknown %v>".
func Repr(v interface{}, indent int) string {
switch v := v.(type) {
case nil:
return "$nil"
case bool:
if v {
return "$true"
}
return "$false"
case string:
return parse.Quote(v)
case int:
return "(num " + strconv.Itoa(v) + ")"
case *big.Int:
return "(num " + v.String() + ")"
case *big.Rat:
return "(num " + v.String() + ")"
case float64:
return "(num " + formatFloat64(v) + ")"
case Reprer:
return v.Repr(indent)
case File:
return fmt.Sprintf("<file{%s %d}>", parse.Quote(v.Name()), v.Fd())
case List:
b := NewListReprBuilder(indent)
for it := v.Iterator(); it.HasElem(); it.Next() {
b.WriteElem(Repr(it.Elem(), indent+1))
}
return b.String()
case Map:
builder := NewMapReprBuilder(indent)
for it := v.Iterator(); it.HasElem(); it.Next() {
k, v := it.Elem()
builder.WritePair(Repr(k, indent+1), indent+2, Repr(v, indent+2))
}
return builder.String()
case StructMap:
return reprStructMap(v, indent)
case PseudoStructMap:
return reprStructMap(v.Fields(), indent)
default:
return fmt.Sprintf("<unknown %v>", v)
}
}
func reprStructMap(v StructMap, indent int) string {
vValue := reflect.ValueOf(v)
vType := vValue.Type()
builder := NewMapReprBuilder(indent)
it := iterateStructMap(vType)
for it.Next() {
k, v := it.Get(vValue)
builder.WritePair(Repr(k, indent+1), indent+2, Repr(v, indent+2))
}
return builder.String()
}