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Search found 9 results on 1 pages for 'r6rs'.

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• Do you have to use display to output stuff using r6rs?

  - by incrediman

  Background: I am new to scheme, and am using DrScheme to write my programs. The following program outputs 12345 when I run the program as r5rs: 12345 However the following program outputs nothing (it's an r6rs program): #!r6rs (import (rnrs)) 12345 That being said, I can get it to output 12345 by doing this: #!r6rs (import (rnrs)) (display 1235) Is that something new with r6rs, where output only occurs when specifically specified using display? Or am I just doing something else wrong

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• How to throw and handle exceptions in R6RS Scheme

  - by Kyle Krull

  What is the standard way to throw and catch exceptions in R6RS Scheme? I'm looking for syntax that works in any version of Scheme (not just PLT) that implements R6RS. R6RS guard syntax looks like it might fit the bill, but can somebody show me an example of how to actually use it?

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• Why do all procedures have to be defined before the compiler sees them?

  - by incrediman

  For example, take a look at this code (from tspl4): (define proc1 (lambda (x y) (proc2 y x))) If I run this as my program in scheme... #!r6rs (import (rnrs)) (define proc1 (lambda (x y) (proc2 y x))) I get this error: expand: unbound identifier in module in: proc2 ...This code works fine though: #!r6rs (import (rnrs)) (define proc2 +) (define proc1 (lambda (x y) (proc2 y x))) (display (proc1 2 3)) ;output: 5

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• Can someone explain the concept of 'hygiene' to me (I'm a scheme programmer)?

  - by incrediman

  So... I'm new to scheme r6rs, and am learning macros. Can somebody explain to me what is meant by 'hygiene'? Thanks in advance.

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• What problems are solved with R6RS Scheme's make-variable-transformer?

  - by Michael Conner

  While looking at the syntax-case section in R6RS, I saw the keyword make-variable-transformer, described as an identifier macro. The example given is very minimal, and I am not groking why it is necessary, or what use-cases require it. Finding additional examples of its use is also proving difficult. Presumably it makes some form of syntax transformation possible, or more elegant?

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• Can't understand example using continuations

  - by Matt Fenwick

  I'm reading the r6rs Scheme report and am confused by the explanation of continuations (I find it to be too dense and lacking of examples for a beginner). What is this code doing and how does it evaluate to 4? Why does call/cc want an argument that's a function of one argument? How is call/cc's argument used? (+ 1 (call-with-current-continuation (lambda (escape) (+ 2 (escape 3))))) =? 4 This example is from section 1.11 - Continuations.

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• What Scheme Does Ghuloum Use?

  - by Don Wakefield

  I'm trying to work my way through Compilers: Backend to Frontend (and Back to Front Again) by Abdulaziz Ghuloum. It seems abbreviated from what one would expect in a full course/seminar, so I'm trying to fill in the pieces myself. For instance, I have tried to use his testing framework in the R5RS flavor of DrScheme, but it doesn't seem to like the macro stuff: src/ghuloum/tests/tests-driver.scm:6:4: read: illegal use of open square bracket I've read his intro paper on the course, An Incremental Approach to Compiler Construction, which gives a great overview of the techniques used, and mentions a couple of Schemes with features one might want to implement for 'extra credit', but he doesn't mention the Scheme he uses in the course. Update I'm still digging into the original question (investigating options such as Petit Scheme suggested by Eli below), but found an interesting link relating to Gholoum's work, so I am including it here. [Ikarus Scheme](http://en.wikipedia.org/wiki/Ikarus_(Scheme_implementation)) is the actual implementation of Ghuloum's ideas, and appears to have been part of his Ph.D. work. It's supposed to be one of the first implementations of R6RS. I'm trying to install Ikarus now, but the configure script doesn't want to recognize my system's install of libgmp.so, so my problems are still unresolved. Example The following example seems to work in PLT 2.4.2 running in DrEd using the Pretty Big (require lang/plt-pretty-big) (load "/Users/donaldwakefield/ghuloum/tests/tests-driver.scm") (load "/Users/donaldwakefield/ghuloum/tests/tests-1.1-req.scm") (define (emit-program x) (unless (integer? x) (error "---")) (emit " .text") (emit " .globl scheme_entry") (emit " .type scheme_entry, @function") (emit "scheme_entry:") (emit " movl $~s, %eax" x) (emit " ret") ) Attempting to replace the require directive with #lang scheme results in the error message foo.scm:7:3: expand: unbound identifier in module in: emit which appears to be due to a failure to load tests-driver.scm. Attempting to use #lang r6rs disables the REPL, which I'd really like to use, so I'm going to try to continue with Pretty Big. My thanks to Eli Barzilay for his patient help.

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• Scheme: Detecting duplicate elements in a list

  - by Kyle Krull

  Does R6RS or Chez Scheme v7.9.4 have a library function to check if a list contains duplicate elements? Alternatively, do either have any built in functionality for sets (which dis-allow duplicate elements)? So far, I've only been able to find an example here. The problem with that is that it doesn't appear to actually be part of the Chez Scheme library. Although I could write my own version of this, I'd much rather use a well known, tested, and maintained library function - especially given how basic an operation this is. So a simple "use these built-in functions" or a "no built-in library implements this" will suffice. Thanks!

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• Rewriting UNIX cal(1)

  - by dharmatech

  Hello, Today I was testing out SRFI 19 and wrote a simple version of the UNIX cal(1) command. Here's a version in R6RS Scheme which runs in Ikarus and Ypsilon. A few example runs. Schemers: How would you write it? Use your favorite implementation. Ruby and Python: I'm guessing that y'all have elegant date and time libraries. I'm sure you can put the Schemers to shame. ;-) Let's see what ya got. I'd also like to see Haskell and golfed versions. Is there a Stack Overflow tag for re-implementations of UNIX commands? :-) Ed

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