Chapter 1. Values and types

This chapter describes the value types that are available in a Yewslip program.

Yewslip is a dynamically typed language. Variables do not have defined types, rather, each value has an associated type. Values of different types may be used together in expressions; operators have specific rules of handling these cases.


The nil value represents an absence of value. Most operations with a nil value yield a nil result. The nil result is also returned from a function that failed. When used in arithmetic expressions, nil is equivalent to 0.

Yewslip> print nil

Yewslip> print 1 - nil

Yewslip> print "text" + nil

Yewslip> print 0 / 0  /* this is undefined */