2.6 Pict-Staging Helper

► |  | Slideshow: Figure and Presentation Tools

1 | Creating Slide Presentations
2 | Making Slides
3 | Typesetting Racket Code in Slideshow
4 | Animations
5 | Legacy Libraries
| Bibliography
| Index

▼ | 2 | Making Slides

2.1 | Primary Slide Functions
2.2 | Slide Registration
2.3 | Viewer Control
2.4 | Constants and Layout Variables
2.5 | Configuration
2.6 | Pict-Staging Helper
2.7 | Text Formatting Helpers
2.8 | Slides to Picts

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with-steps
with-steps~

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#### 2.6`` Pict-Staging Helper

(require slideshow/step) | package: slideshow-lib

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.

> syntax (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.

> syntax (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 of the last id name ends in ~).
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