langur

operators, precedence, and associativity

Langur uses the following, in order of descending precedence.

See the numbers page for math operator descriptions.

the forward operator

The -> operator (forward operator) forwards a value to a function or a regex. This may be used within a switch to match a value against a regex.

is/is not operators

The is and is not operators are used with a type as the right operand, such as string or list. See the type page for details.

in/not in and of/not of operators

The in operator tests whether a value exists within a composed value. The of operator tests whether a hypothetical index value is valid for a composed value.

These should not be confused with for in/for of loops, which are automated loops.

append operator

The append operator works between 2 strings, 2 lists, or 2 hashes.

It can also be used between a string and integer or between 2 integers (code points), generating a string.

Using append between hashes will silently overwrite if keys in the right hash match keys in the left hash. If you use the more() function instead to add to a hash, it will not overwrite, but throw an exception for matching keys.

Appending null to anything acts as a no-op (evaluates to left operand) instead of throwing an exception. Note that this is not how the more() function treats null.

Boolean multiplication

Values of types which have a zero value (number, string, list, hash, and duration) may be multiplied with a Boolean to receive the original value (if true) or the zero value (if false).

"string" * (value > 10) # yields "string" if expression true and zero-length string if false

combination operators

Infix logical and mathematical operators, and the append operator, can be used as combination operators with assignment. For example, writing x += 1 is the same as writing x = x + 1.

It is as though the right-hand is wrapped in parentheses, so that x *= a + b is the equivalent of x = x * (a + b), not x = x * a + b (which would be different because of operator precedence).

null-propagating operators

Normal operators treat null as an ordinary value (don't favor propagating null). Testing null == null returns true and null == false returns false.

Operators ending with ? are null-propagating (or "database") operators. For these, if either side is null, the result is null. Testing null ==? anything returns null.

short-circuiting operators

The and, or, nand and nor operators are short-circuiting.

Null-propagating operators are short-circuiting in a different manner (only if the left value is null). This includes all infix operators that end with ?, such as and?, nor?, ==?, xor?, etc.

composite comparisons

Items of the same type (lists, hashes, or ranges) may be directly compared for equality or inequality.