Newbie: Setting definitions in pollen.rkt

[Jen Hutton]

I'm new to Pollen/Racket and I'm working on converting a small book project to an e-book as practice. The book is text and image, so I've been playing around with the pict and 2htdp libraries to draw the images for each page. 

The drawings are based on a shared library of simple geometric shapes, so I thought I could define all of the components and color palette in pollen.rkt and then call the ones I need in my html.pm pages (it's a long list for the entire book). I keep hitting a contract violation when I run the pages, and not sure why—tbh, contracts and how to troubleshoot them is a little out of my wheelhouse right now. 

Any help is appreciated—thanks.

pollen,rkt:

#lang racket/base

(require (prefix-in htdp: 2htdp/image)

         lang/posn

         pict

         racket/class pict)

; primary shape

(define rect (filled-rectangle 152 178))

(define bar-x (filled-rectangle 154 8))

(define bar-y (filled-rectangle 8 180))

; secondary shapes 

(define half-moon (clip-ascent (filled-ellipse 75 75)))

(define patch (filled-rectangle 73 83))

; spacers

(define gutter 15)

(define deg 0.2)

; the color palette

(define orange (list 255 102 51))

(define purple (list 38 13 38))

(define green (list 10 41 26))

(provide pict-as-png)

(define (pict-as-png pict)

  (let ([png-name (format "~a.png" (gensym))])

    (send (pict->bitmap pict) save-file png-name 'png)

    `(img ((src ,png-name)))))

page1.html.pm:

#lang pollen

◊(pict-as-png

  (hbl-append ◊|gutter|

    (shear (colorize ◊|rect| ◊|orange|) 0 ◊|deg|)

    (shear (colorize ◊|rect| ◊|orange|) 0 -0.2))

)

pict->bitmap: contract violation
  expected: pict-convertible?
  given: '(hbl-append 15 (shear (colorize #<procedure:pollen-tag:filled-rectangle> "orange") 0 0.2) (shear (colorize #<procedure:pollen-tag:filled-rectangle> "orange") 0 -0.2))
...

  contract from: <pkgs>/pict-lib/pict/main.rkt

[Evžen Wybitul]

It seems hbl-append isn’t recognized as a function, so it defaults to a pollen tag (quoted TXEXP). I’d recommend you to explicitly require the module which exports the hbl-append function in the .pm file, or explicit lying provide the function in pollen.rkt. I can’t test it myself right now, but that should help.

[Jen Hutton]

Thanks. That fixed it, as well as adding (provide (all-defined-out)) to pollen.rkt. I seemed to have left that out too.

[Matthew Butterick]

> On 07 26 19, at 3:03 PM, Jen Hutton <jenh...@gmail.com> wrote:
>
> Thanks. That fixed it, as well as adding (provide (all-defined-out)) to pollen.rkt. I seemed to have left that out too.

BTW though you can `require` any module within a Pollen source file, for instance:

#lang pollen
(require certain/module)
···

You can also propagate it via "pollen.rkt" with `all-from-out`, for instance:

#lang racket
(require certain/module)
(provide (all-from-out certain/module))
···


This has the same effect, because anything exported from "pollen.rkt" is implicitly available in a Pollen source file that relies on it.

[Matthew Butterick]

Whoops that first example was missing a lozenge, should’ve been like so:

#lang pollen

◊(require certain/module)
···

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[Jen Hutton]

That works too! I'll go with that so my source files stay cleaner. Thanks.

On Friday, July 26, 2019 at 9:30:15 PM UTC-7, Matthew Butterick wrote:

Whoops that first example was missing a lozenge, should’ve been like so:

#lang pollen

◊(require certain/module)
···

On Jul 26, 2019, at 7:57 PM, Matthew Butterick <m...@mbtype.com> wrote:

On 07 26 19, at 3:03 PM, Jen Hutton <jenh...@gmail.com> wrote:

Thanks. That fixed it, as well as adding (provide (all-defined-out)) to pollen.rkt. I seemed to have left that out too.

BTW though you can `require` any module within a Pollen source file, for instance:

#lang pollen
(require certain/module)
···

You can also propagate it via "pollen.rkt" with `all-from-out`, for instance:

#lang racket
(require certain/module)
(provide (all-from-out certain/module))
···


This has the same effect, because anything exported from "pollen.rkt" is implicitly available in a Pollen source file that relies on it.


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