Combiner

Reverses the argument order of a combiner's combine method.

When to use

Use when you want the right-hand value to act as the accumulator, or need to reverse a non-commutative combiner such as string concatenation.

Details

Returns a new Combiner where combine(self, that) calls the original combiner as combine(that, self).

See

• make

Wraps a Combiner so that a separator value is inserted between every pair of combined elements.

When to use

Use when you need to inject a fixed separator between accumulated values, such as when building delimited strings, paths, or CSV-like output by repeated combination.

Details

intercalate(middle)(combiner).combine(self, that) is equivalent to combiner.combine(self, combiner.combine(middle, that)). This function is curried: first provide the separator, then the base combiner.

See

• make

Creates a Combiner that ignores both arguments and always returns the given constant value.

When to use

Use when you need a combiner that always returns a fixed value, including when a generic API requires a combiner but the result is predetermined.

Details

combine(self, that) returns the constant a and ignores both arguments.

See

• first
• last

Creates a Combiner that always returns the first (left) argument.

When to use

Use when you want "first write wins" semantics while merging values.

Details

combine(self, that) returns self and ignores that.

See

• last

Creates a Combiner that always returns the last (right) argument.

When to use

Use when you want "last write wins" semantics while merging values.

Details

combine(self, that) returns that and ignores self.

See

• first

Creates a Combiner from a binary function.

When to use

Use when you have a custom combining operation that is not covered by the built-in constructors (min, max, first, last, constant).

Details

The returned combiner's combine method delegates to the provided function. Any purity, associativity, or mutation behavior comes from that function.

See

• Combiner – the interface this creates

Creates a Combiner that returns the larger of two values according to the provided Order.

When to use

Use when you want to accumulate the maximum value across a collection or build a Reducer that tracks the running maximum.

Details

The combiner compares values using the given Order. When values are equal, it returns that (the second argument).

See

• min

Creates a Combiner that returns the smaller of two values according to the provided Order.

When to use

Use when you want to accumulate the minimum value across a collection or build a Reducer that tracks the running minimum.

Details

The combiner compares values using the given Order. When values are equal, it returns that (the second argument).

See

• max

Represents a strategy for combining two values of the same type A. A Combiner contains a single combine method that takes two values and returns a merged result. It does not include an identity/empty value; use Reducer when you need one.

When to use

Use when you need to describe how two values of the same type merge, pass a reusable combining strategy to library functions like Struct.makeCombiner or Option.makeCombinerFailFast, or define the combining step for a Reducer.

See

• make – create a Combiner from a function