3.6 Pict-Staging Helper

The slideshow/step library provides syntax for breaking a complex slide into steps that are more complex than can be handled with 'next and 'alts in a slide sequence.

(with-steps (id ...) body ...)

Evaluates the bodys once for each id, skipping an id if its name ends with ~ and condense? is true. The results of the last body for each iteration are collected into a list, which is the result of the with-steps form.

Within the bodys, several keywords are bound non-hygienically (using the first body’s lexical context):

(only? id) — returns #t during the id step (i.e., during the evaluation of the bodys for id), #f otherwise.
(vonly id) — returns the identity function during the id step, ghost otherwise.
(only id then-expr) returns the result of then-expr during the id step, values otherwise.
(only id then-expr else-expr) returns the result of then-expr during the id step, the result of else-expr otherwise.
(before? id) — returns #t before the id step, #f starting for the id and afterward.
(vbefore id), (before id then-expr), or (before id then-expr else-expr) — analogous to vonly and only.
(after? id) — returns #t after the id step, #f through the id step.
(vafter id), (after id then-expr), or (after id then-expr else-expr) — analogous to vonly and only.
(between? a-id b-id) — returns #t starting from the a-id step through the b-id step, #f otherwise.
(vbetween a-id b-id), (between a-id b-id then-expr), or (between a-id b-id then-expr else-expr) — analogous to vonly and only.
(between-excel? a-id b-id) — returns #t starting from the a-id step through steps before the b-id step, #f for the b-id step and afterward.
(vbetween-excl a-id b-id), (between-excl a-id b-id then-expr), or (between-excl a-id b-id then-expr else-expr) — analogous to vonly and only.

(with-steps~ (id ...) body ...)

Like with-steps, but when condense? is true, then expr is evaluated only for the last id (independent of whether the name fo the last id name ends in ~).

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1	Creating Slide Presentations
2	Making Pictures
3	Making Slides
4	Typesetting Racket Code
5	Animations
	Bibliography
	Index

3.1	Primary Slide Functions
3.2	Slide Registration
3.3	Viewer Control
3.4	Constants and Layout Variables
3.5	Configuration
3.6	Pict-Staging Helper
3.7	Slides to Picts