I'm looking for a way to import a .jpg file into R5RS. I would like to use it as background for a game that I'm making.
Thanks!
Many Scheme implementations have support for image files. The R5RS standard, as written, does not. I suggest using Racket, where you can use, e.g.,
(require 2htdp/image)
(bitmap/file "/path/to/foo.jpg")
In fact, there are many parts of building a game that are not going to fit well under the R5RS umbrella. I'm afraid you're almost certainly going to have to pick an implementation, and use features that lie outside of the standard.
I use the graphics/graphics library.
Put it in your file by using this (in racket):
(require graphics/graphics)
This is the usage:
((draw-pixmap viewport) file p [color]) → void?
viewport : viewport?
file : path-string?
p : posn?
color : (or/c (integer-in 0 299)
string?
rgb?)
You can find more help in the Racket documentation
Related
I was trying to follow how to do scheme and sicp from Which lang packet is proper for SICP in Dr.Racket?
but when I run code in the accepted answer
#lang sicp
(paint-highres (below (beside diagonal-shading
(rotate90 diagonal-shading))
(beside (rotate270 diagonal-shading)
(rotate180 diagonal-shading))))
I get error
paint-hires: unbound identifier in: paint-hires
I have installed the sicp package.
Anyone know what the problem is?
The paint-hires function is a left-over form the original MIT Scheme implementation. Back then it the "high resolution" was too slow to use, while experimenting - so paint-hires was used to get a "final" image.
When the original MIT Scheme implementation of the SICP Picture Language was ported to PLT Scheme paint-hires was kept.
Recently (within a year or two) the SICP Picture Language was reimplemented on modern Racket. This gives you the ability to use the Picture language with a resolution of your choice, colors! (the original MIT Scheme was used on monochrome displays) and more.
Make a copy of: "main.rkt" and einstein2.jpg" and save them in the same folder.
Open "main.rkt" in DrRacket and run it.
Look at the bottom for examples.
Add your own program at the bottom of "main.rkt".
Look through the files for how to use colors etc.
Both files are here:
https://github.com/sicp-lang/sicp/tree/master/sicp-pict
#sorawee-porncharoenwase thank you for the docs link. #soegaard thanks for the context for the recent changes to DrRacket.
What finally worked for me was this
#lang sicp
(#%require sicp-pict)
(paint (below (beside diagonal-shading
(rotate90 diagonal-shading))
(beside (rotate270 diagonal-shading)
(rotate180 diagonal-shading))))
I think the docs incorrectly say to use paint-hires.
I'm trying to use the racket CLI to run a file but I need a specific language (pretty-big) features to be available and I'm struggling with that.
As far as I know, if I run $ racket <file_name> then it requires the file as a module. In order to do that, I need to add #lang <some_lang> at the top of my file, but I just can't find any equiv to #lang pretty-big. Any idea how to ask for pretty-big this way?
The other option, is to run the code in load-mode (from the racket CLI manual) but on this case I'm getting no results back which obviously isn't good.
Any suggestions?
I know the solution to this will be super easy, just can't find it.
A search of the Racket docs for "pretty big" turned up this result, which says that the module lang/plt-pretty-big corresponds to DrRacket's "Pretty Big" legacy language.
Unfortunately, putting
#lang lang/plt-pretty-big
at the top of your file won't work, because that module doesn't specify a reader. But you can tell it to use the usual S-expression reader by using the s-exp "meta-language" as follows:
#lang s-exp lang/plt-pretty-big
If you want Racket to print out the results of top-level expressions in your file, it looks like the lang/plt-pretty-big language still won't do it, and I don't think there's an easy fix. Consider porting the program to #lang racket, which has that behavior. Or add println around the things you want printed.
I'm trying to implement some of SICP graphic programs in Racket, but there are 2 problems:
When I need to use 'let' I can't use beginner language.
When I try to change language, or open new file while using "advanced" language, I get this error:
module: identifier already imported from a different source
error when I try to load image module by (require 2htdp/image).
What's going on? Also, are there better ways to train with images in Scheme?
It's not clear why you want to use 2htdp/image in the first place. A much more useful package to use would be Neil Van Dyke's SICP Support page, it provides a language with support for the book and includes the graphical language. That should be enough to solve both of your problems.
As Óscar mentions, you are better off with using #lang planet neil/sicp, However, if you want to import somethng that exports identical symbols you can prefix them:
(require (prefix-in hi: 2htdp/image))
Then all exported from that have prefix hi:, eg. (hi:circle 30 "outline" "red"). The colon isn't anything special. The prefix could have been xxx and it would be xxxcircle.
Also, you can only import the symbols you want:
; you only want circle and eclipse
(require (only-in 2htdp/image circle ellipse))
Or you can import everything except some symbols:
; everything except circle and ellipse
(require (except-in 2htdp/image circle))
And there is no reason not using racket or racket/base as language when you know this.
Anyone know what is included in the racket/base language. I am looking to compare the racket/base namespace definitions with the R7RS draft to get a first hand idea of how divergent Racket is from Scheme.
The difference is going to be huge, just like any other practical Scheme implementation. To give you a rough idea, I see more than 1300 identifiers from racket/base, and racket goes up to over 2000. Also, note that comparing the names is not going to be the whole story -- there are additional differences, like the fact that Racket uses immutable pairs by default, and like the fact that you get guaranteed left-to-right evaluation order.
A quick way to get the lists yourself for the former would be to make sure that XREPL is installed (have your ~/.racketrc file contain (require xrepl)), then start Racket with racket/base as the REPL language, and use the ,ap (apropos) command with no arguments so it shows you all of the bound names:
$ racket -I racket/base
Welcome to Racket v5.2.1.
-> ,ap
To read about the names, you can use the ,doc command, or just use the search box in the docs.
According to The Racket Reference:
Unless otherwise noted, the bindings defined in this manual are exported by the racket/base and racket languages.
Unfortunately that is not terribly helpful since it is a large reference manual. But, since you are comparing R7RS to Racket, it may be useful to just browse through the whole reference to get an idea of what is available.
I've got a bunch of "legacy" Guile Scheme code that I want to get running in the Racket Scheme IDE. There appear to be enough differences to make this a non-trivial exercise. (My level of Scheme knowledge is the level to complete the The Little Schemer).
My question is:
What are the differences between Guile Scheme and Standard Scheme (in the Racket IDE)?
In light of these differences, in general, what are the steps I'll need to take to convert some Guile Scheme Code to standard Scheme?
Additional: (happy with divergence between Racket Scheme and R5RS/R6RS) - what I want is to get 'something' to run in the Racket IDE - rather than the Racket language.
If by "Standard Scheme (in the Racket IDE)," you mean the Racket language, i.e., what you get when you prefix your code with #lang racket, then the top four differences to look out for are:
a different module system
a different macro system (depending on how old your code is)
immutable cons-cells (unless you import mutable ones)
no one-armed ifs in Racket (use when)
To port code from Guile to Racket, find out which files are "at the bottom" of your dependencies, i.e., find the files that do not depend on other files.
Open such a file in Racket, add the line #lang racket at the top, and try to run it.
You will most likely encounter some "unbound identifier" errors.
If you are lucky, the function is present in Racket, but not included in the "racket" language. Search for the name in the Racket documentation, and if you find it, then use (require ...) to import the name into your program.
Then run the program again to find the next error.
Some function are named differently in Guile and Racket, so look up the name in the Guile documentation and see what it does. Then open the Racket documentation on the same subject, and see what it is called in Racket.
In some cases you may have to make bigger changes. If you can't find some piece of functionality in the Racket documentation, then try asking the mailing list. It could be that it simply has a different name, or that somebody implemented it and put it on PLaneT (thus it will no appear in the documentation until you have installed the package).
Example of importing srfi/1 into the R5RS language.
#lang r5rs
(#%require srfi/1)
(xcons 1 2)
Differences from R4RS code to modern Scheme?
One thing to look out for is that in R4RS the empty list '() counted as false, not it is interpreted as true.
See this question for more things to look out for:
Running SICP Pattern Matching Rule Based Substitution Code
See also this list of changes from the R5RS standard:
List of changes from R4RS to R5RS