reduce( function, initial, list, context )
Calls a rule or function for each item in a list, passing the result of each call to the next one, and returns the value of the last computation.
Keyword  Type  Description 


Rule or Function Reference 
Rule or expression function. 

Any Type 
The accumulator's initial value. 

Any Type 
Array of elements that the function iterates through. 

Any Type Array 
Variable number of parameters passed directly into each function evaluation. 
Any Type
Use fn!functionName
to reference an expression function and rule!ruleName
to reference a rule.
The initial accumulator value is given by initial.
To use rules or functions that take more than two arguments, use the merge() function. For example, given a rule g(x, y, z)
, reduce(rule!g, i, merge({a, b, c}, {d, e, f}))
returns g(g(g(i, a, d), b, e), c, f)
.
Null lists return a null list without executing the function.
Returns a scalar value if the function called returns a scalar, and returns a list if the function called returns a list.
Best used when the computation of each operation needs to use the result from the previous operation such as when the result of each operation is an array that should be appended to each other in order. The result from the previous operation is then passed to the subsequent operation as the parameter initial.
a!forEach()
cannot be used within rules used in this function.
Given a function h(x, y)
, reduce(fn!h,initial, {a, b, c}, v)
returns h(h(h(initial, a, v), b, v), c, v)
.
reduce(fn!sum, 0, {1, 2, 3})
returns 6