added

vendor/github.com/glycerine/zygomys/zygo/strutils.go

@@ -0,0 +1,63 @@
+package zygo
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+func ConcatStr(str *SexpStr, rest []Sexp) (*SexpStr, error) {
+	res := &SexpStr{S: str.S}
+	for i, x := range rest {
+		switch t := x.(type) {
+		case *SexpStr:
+			res.S += t.S
+		case *SexpChar:
+			res.S += string(t.Val)
+		default:
+			return &SexpStr{}, fmt.Errorf("ConcatStr error: %d-th argument (0-based) is "+
+				"not a string (was %T)", i, t)
+		}
+	}
+
+	return res, nil
+}
+
+func AppendStr(str *SexpStr, expr Sexp) (*SexpStr, error) {
+	var chr *SexpChar
+	switch t := expr.(type) {
+	case *SexpChar:
+		chr = t
+	case *SexpStr:
+		return &SexpStr{S: str.S + t.S}, nil
+	default:
+		return &SexpStr{}, errors.New("second argument is not a char")
+	}
+
+	return &SexpStr{S: str.S + string(chr.Val)}, nil
+}
+
+func StringUtilFunction(env *Zlisp, name string, args []Sexp) (Sexp, error) {
+	if len(args) != 1 {
+		return SexpNull, WrongNargs
+	}
+	var s string
+	switch str := args[0].(type) {
+	case *SexpStr:
+		s = str.S
+	default:
+		return SexpNull, fmt.Errorf("string required, got %T", s)
+	}
+
+	switch name {
+	case "chomp":
+		n := len(s)
+		if n > 0 && s[n-1] == '\n' {
+			return &SexpStr{S: s[:n-1]}, nil
+		}
+		return &SexpStr{S: s}, nil
+	case "trim":
+		return &SexpStr{S: strings.TrimSpace(s)}, nil
+	}
+	return SexpNull, fmt.Errorf("unrecognized command '%s'", name)
+}