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## step_zero

Combinator

Like [step] but with 0 as the initial value.

       [...] [F] step_zero
    -------------------------
         0 [...] [F] step

### Definition

> 0 [roll>] [step]

### Discussion

[size] and [sum] can both be defined in terms of this specialization of
[step].

### Crosslinks

[step]

