github.com/kolbycrouch/elvish@v0.14.1-0.20210614162631-215b9ac1c423/pkg/eval/vals/repr.go (about)

     1  package vals
     2  
     3  import (
     4  	"fmt"
     5  	"math"
     6  	"math/big"
     7  	"reflect"
     8  	"strconv"
     9  
    10  	"src.elv.sh/pkg/parse"
    11  )
    12  
    13  // NoPretty can be passed to Repr to suppress pretty-printing.
    14  const NoPretty = math.MinInt32
    15  
    16  // Reprer wraps the Repr method.
    17  type Reprer interface {
    18  	// Repr returns a string that represents a Value. The string either be a
    19  	// literal of that Value that is preferably deep-equal to it (like `[a b c]`
    20  	// for a list), or a string enclosed in "<>" containing the kind and
    21  	// identity of the Value(like `<fn 0xdeadcafe>`).
    22  	//
    23  	// If indent is at least 0, it should be pretty-printed with the current
    24  	// indentation level of indent; the indent of the first line has already
    25  	// been written and shall not be written in Repr. The returned string
    26  	// should never contain a trailing newline.
    27  	Repr(indent int) string
    28  }
    29  
    30  // Repr returns the representation for a value, a string that is preferably (but
    31  // not necessarily) an Elvish expression that evaluates to the argument. If
    32  // indent >= 0, the representation is pretty-printed. It is implemented for the
    33  // builtin types nil, bool and string, the File, List and Map types, StructMap
    34  // types, and types satisfying the Reprer interface. For other types, it uses
    35  // fmt.Sprint with the format "<unknown %v>".
    36  func Repr(v interface{}, indent int) string {
    37  	switch v := v.(type) {
    38  	case nil:
    39  		return "$nil"
    40  	case bool:
    41  		if v {
    42  			return "$true"
    43  		}
    44  		return "$false"
    45  	case string:
    46  		return parse.Quote(v)
    47  	case int:
    48  		return "(num " + strconv.Itoa(v) + ")"
    49  	case *big.Int:
    50  		return "(num " + v.String() + ")"
    51  	case *big.Rat:
    52  		return "(num " + v.String() + ")"
    53  	case float64:
    54  		return "(num " + formatFloat64(v) + ")"
    55  	case Reprer:
    56  		return v.Repr(indent)
    57  	case File:
    58  		return fmt.Sprintf("<file{%s %d}>", parse.Quote(v.Name()), v.Fd())
    59  	case List:
    60  		b := NewListReprBuilder(indent)
    61  		for it := v.Iterator(); it.HasElem(); it.Next() {
    62  			b.WriteElem(Repr(it.Elem(), indent+1))
    63  		}
    64  		return b.String()
    65  	case Map:
    66  		builder := NewMapReprBuilder(indent)
    67  		for it := v.Iterator(); it.HasElem(); it.Next() {
    68  			k, v := it.Elem()
    69  			builder.WritePair(Repr(k, indent+1), indent+2, Repr(v, indent+2))
    70  		}
    71  		return builder.String()
    72  	case StructMap:
    73  		return reprStructMap(v, indent)
    74  	case PseudoStructMap:
    75  		return reprStructMap(v.Fields(), indent)
    76  	default:
    77  		return fmt.Sprintf("<unknown %v>", v)
    78  	}
    79  }
    80  
    81  func reprStructMap(v StructMap, indent int) string {
    82  	vValue := reflect.ValueOf(v)
    83  	vType := vValue.Type()
    84  	builder := NewMapReprBuilder(indent)
    85  	it := iterateStructMap(vType)
    86  	for it.Next() {
    87  		k, v := it.Get(vValue)
    88  		builder.WritePair(Repr(k, indent+1), indent+2, Repr(v, indent+2))
    89  	}
    90  	return builder.String()
    91  }