set nya as 0

Author: mengzhuo

Diff for: .gitignore

@@ -14,3 +14,4 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
+main.wasm

Diff for: README.md

@@ -55,7 +55,7 @@ sada
 
 * `da` True in boolean
 * `nye` False in boolean
-* `nya` null, nil
+* `nya` null, nil, 0
 * `unu` one, 1
 * `du` two, 2
 * `unudu` three, 3

Diff for: elementary.go

@@ -94,6 +94,9 @@ func truthExpr(t bool) *Expr {
 }
 
 func (c *Context) getNumber(expr *Expr) int {
+	if expr.isNya() {
+		return 0
+	}
 	if !expr.isNumber() {
 		errorf("expect number; got %v", expr)
 	}

Diff for: eval.go

@@ -344,6 +344,10 @@ func (e *Expr) isTrue() bool {
 	return e != nil && e.sada == tokDa
 }
 
+func (e *Expr) isNya() bool {
+	return e == nil || e.sada == tokNya
+}
+
 func (e *Expr) length() int {
 	if e == nil {
 		return 0