• Operator Precedence
• Mathematical Operators
• Equality & Comparison Operators
• Logical Operators
• The Conditional Operator
• The Null-coalescing Operator
• The Error-coalescing Operator
• The Else-coalescing Operator
• Assignment Operators
• Overloading Operators

Operator Precedence

Operator precedence in the table below goes from high at the top to low at the bottom. Operators at the same level have the same precedence.

Note that conditional expressions using the ternary operator ? :| can't be nested. (Checkmate, Satan.)

Mathematical Operators

You can overload the mathematical operators to customize their behaviour for your own types.

Equality & Comparison Operators

The equality (==, !=) and comparison (>, >=, <, <=) operators each take two operands and evaluate to a boolean.

• Numbers are equal if their values are numerically equal.
• Strings are equal if they have the same content.
• Tuples are equal if they have the same length and their elements are equal.
• Sets are equal if they are set-equivalent, i.e. if they contain the same items in any order.
• By default, all other objects are equal only if they are the same object.

You can overload the equality and comparison operators to customize their behaviour for your own types.

Logical Operators

The logical operators are || (OR), && (AND), and ! (NOT). They evaluate the truthiness of their operands.

In Pyro, the values false, null, and err are falsey; all other values are truthy.

The logical operators || and && are short-circuiting.

The value of the logical-OR expression a || b is the value of the first operand if that operand is truthy, otherwise the value of the second operand.

This means you can use the || operator to swap in a default value in place of a falsey expression, e.g.

var value = maybe_falsey() || "default";

Note that you can chain multiple || expressions, e.g.

var value = maybe_falsey() || get_fallback() || "default";

The value of the logical-AND expression a && b is the value of the first operand if that operand is falsey, otherwise the value of the second operand.

This means you can use the && operator to conditionally chain a sequence of expressions, e.g.

func1() && func2();

func2() will only be called if func1() returns a truthy value.

Note that you can chain multiple && expressions, e.g.

func1() && func2() && func3();

func2() will only be called if func1() returns a truthy value; func3() will only be called if func2() returns a truthy value.

The Conditional Operator

The conditional or ternary operator takes three operands. It looks like this:

var value = condition ? expr1 :| expr2;

The value of the conditional expression is expr1 if condition evaluates as truthy, otherwise expr2.

The Null-coalescing Operator

The null-coalescing operator ?? lets you swap in a default value in place of a null:

var value = maybe_null() ?? "default";

The value of the expression a ?? b is the value of the first operand if that operand is not null, otherwise the value of the second operand.

You can chain multiple ?? expressions, e.g.

var value = maybe_null() ?? get_fallback() ?? "default";

The Error-coalescing Operator

The error-coalescing operator !! lets you swap in a default value in place of an error:

var value = maybe_error() !! "default";

The value of the expression a !! b is the value of the first operand if that operand is not an err, otherwise the value of the second operand.

You can chain multiple !! expressions, e.g.

var value = maybe_error() ?? get_fallback() ?? "default";

The Else-coalescing Operator

The else-coalescing operator else lets you swap in a default value in place of a broadly-defined falsey-ish value:

var value = get_value() else "default";

The value of the expression a else b is the value of the first operand if that value is not one of (false, null, err, 0, 0.0, or ""), otherwise the value of the second operand.

You can chain multiple else expressions, e.g.

var value = get_value() else get_fallback() else "default";

Assignment Operators

An assignment expression, a = b, returns the value assigned, e.g.

var foo;
var bar = (foo = 5);
assert bar == 5;

Assignment using a compound assignment operator, e.g.

foo += bar;

is equivalent to the longform expression:

foo = foo + bar;

Compound assignment operators cannot be overloaded independently of their base operators — i.e. overloading + automatically overloads +=;

Overloading Operators

The following operators can be overloaded by user-defined types:

• ()
• []
• ==
• <
• <=
• >
• >=
• + (binary/unary)
• - (binary/unary)
• *
• **
• /
• //
• %
• &
• |
• ^
• ~
• <<
• >>

You can overload these operators using the $-prefixed methods listed here.