sicmutils.util.stream — net.littleredcomputer/sicmutils 0.13.0

This namespace contains various standard sequences, as well as utilities for working with strict and lazy sequences.

powers clj/s

(powers n)

(powers n x)

Returns an infinite sequence of x * n^i, starting with i == 0. x defaults to 1.

pprint clj/s

(pprint n xs)

Realizes and pretty-prints n elements from the supplied sequence xs.

scan clj/s

(scan f & {:keys [present init] :or {present identity}})

Returns a function that accepts a sequence xs, and performs a scan by:

• Aggregating each element of xs into
• the initial value init
• transforming each intermediate result by present (defaults to identity).

The returned sequence contains every intermediate result, after passing it through present (not init, though).

This is what distinguishes a scan from a 'fold'; a fold would return the final result. A fold isn't appropriate for aggregating infinite sequences, while a scan works great.

Arities:

• the three-arity version takes init value, f fold function and present.
• the two arity version drops init, and instead calls f with no arguments. The return value is the initial aggregator.
• The 1-arity version only takes the merge fn and defaults present to identity.

seq-limit clj/s

(seq-limit xs)

(seq-limit xs
           {:keys [minterms maxterms tolerance convergence-fn fail-fn]
            :or {minterms 2
                 tolerance (Math/sqrt v/machine-epsilon)
                 convergence-fn (close-enuf? tolerance)}})

Accepts a sequence, iterates through it and returns a dictionary of this form:

{:converged? <boolean> :terms-checked <int> :result <sequence element>}

:converged? is true if the sequence reached convergence by passing the tests described below, false otherwise.

:terms-checked will be equal to the number of items examined in the sequence.

:result holds the final item examined in the sequence.

Optional keyword args:

:convergence-fn user-supplied function of two successive elements in xs that stops iteration and signals convergence if it returns true.

:fail-fn user-supplied function of two successive elements in xs that stops iteration and signals NO convergence (failure!) if it returns true.

:minterms seq-limit won't return until at least this many terms from the sequence have been processed.

:maxterms seq-limit will return (with :converged? false) after processing this many elements without passing any other checks.

:tolerance A combination of relative and absolute tolerance. defaults to sqrt(machine epsilon).

zeno clj/s

(zeno n)

(zeno n x)

Returns an infinite sequence of x / n^i, starting with i == 0. x defaults to 1.