Values, variables, and expressions

Goblin is dynamically typed: variables do not declare a type, and values carry their types at runtime. Use var to bind a name to a value.

var project = "Goblin Book"
var published = false

Assign to the name to update it later.

var score = 10
score = score + 5
print(score) # 15

print separates multiple arguments with spaces and ends the line; it writes to stdout. Use eprint for the same formatting on stderr. A comment starts with # and runs to the end of its line.

Operators

The ordinary arithmetic operators are +, -, *, /, and %. The % operator returns the remainder and has the same precedence as multiplication and division. Use parentheses to make grouping explicit.

print(1 + 2 * 3)       # 7
print((1 + 2) * 3)     # 9
print("go" + "blin")  # goblin
print("ha" * 3)        # hahaha
print(10 % 3)          # 1

Comparison operators are ==, !=, <, <=, >, and >=; each produces a boolean. Equality is total across types: values of unrelated types are simply unequal, so x == nil is always a safe test, and lists and dictionaries compare element by element. Ordering comparisons (<, <=, >, >=) raise TypeError when the operands cannot be ordered. Comparisons do not chain: a < b < c is a syntax error rather than the surprising (a < b) < c, so write a < b && b < c, or parenthesize explicitly when you really mean to compare a boolean result. Logical operators are !, &&, and ||. && and || short-circuit, so their right-hand side is evaluated only when needed, and they produce the operand that decided the result rather than a boolean: a || b is a when a is truthy and b otherwise, a && b is a when a is falsy and b otherwise. That makes || the way to write "use this, or a default". Wrap the expression in Bool() when you need a plain true/false. ! always produces a boolean.

var allowed = age >= 18 && !banned
var nickname = supplied || "anonymous"

&& binds tighter than ||, as in most languages: ready || retry && connected evaluates as ready || (retry && connected), and true || false && false produces true.

Conditions use truthiness. false, nil, numeric zero, and empty strings or collections are false. Continue with Built-in types for the values that Goblin provides.