panic: ["a", "b"].sum()

[odino]

panic: interface conversion: object.Object is *object.String, not *object.Integer

goroutine 1 [running]:
abs/evaluator.getFns.func13(0xc4200ec340, 0x1, 0x1, 0x0, 0x0)
	/go/src/abs/evaluator/functions.go:292 +0x1f1
abs/evaluator.applyMethod(0x575940, 0xc42011e1c0, 0xc42013225b, 0x3, 0x0, 0x0, 0x0, 0x1b0000000b, 0x1c0000000e)
	/go/src/abs/evaluator/evaluator.go:605 +0x1d6
abs/evaluator.Eval(0x5757c0, 0xc4200ea240, 0xc420010550, 0x5757c0, 0xc4200ea240)
	/go/src/abs/evaluator/evaluator.go:126 +0xf18
abs/evaluator.Eval(0x575540, 0xc4200f00f0, 0xc420010550, 0x575540, 0xc4200f00f0)
	/go/src/abs/evaluator/evaluator.go:36 +0x101f
abs/evaluator.evalProgram(0xc42011e120, 0xc420010550, 0xc42005fa60, 0x410629)
	/go/src/abs/evaluator/evaluator.go:160 +0xb3
abs/evaluator.Eval(0x575840, 0xc42011e120, 0xc420010550, 0x0, 0x0)
	/go/src/abs/evaluator/evaluator.go:30 +0x2bd
abs/repl.Run(0xc420132250, 0x10, 0x101)
	/go/src/abs/repl/repl.go:107 +0xdc
abs/repl.executor(0xc420132250, 0x10)
	/go/src/abs/repl/repl.go:90 +0x7c
github.com/c-bata/go-prompt.(*Prompt).Run(0xc4200c8000)
	/go/src/github.com/c-bata/go-prompt/prompt.go:73 +0x7b5
abs/repl.Start(0x575120, 0xc42000e010, 0x575140, 0xc42000e018)
	/go/src/abs/repl/repl.go:60 +0xec
main.main()
	/go/src/abs/main.go:25 +0x11f
exit status 2
Makefile:11: recipe for target 'repl' failed
make: *** [repl] Error 1