The amb -< operator is not defined
I see this in the lecture slide
> (+ 10 (-< 1 2 3))
11
> (next)
12
> (next)
13
> (next)
'done
But when I tried it my own in DrRacket, it came up with an error
> (+ 10 (-< 1 2 3))
. . -<: undefined;
cannot reference an identifier before its definition
>
The slide didn't indicate any requirement. I also google "racket -<: undefined", but seems google can't find any result relate to the symbol -<. How can I fix it?
racket
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
add a comment |
I see this in the lecture slide
> (+ 10 (-< 1 2 3))
11
> (next)
12
> (next)
13
> (next)
'done
But when I tried it my own in DrRacket, it came up with an error
> (+ 10 (-< 1 2 3))
. . -<: undefined;
cannot reference an identifier before its definition
>
The slide didn't indicate any requirement. I also google "racket -<: undefined", but seems google can't find any result relate to the symbol -<. How can I fix it?
racket
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
3
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29
add a comment |
I see this in the lecture slide
> (+ 10 (-< 1 2 3))
11
> (next)
12
> (next)
13
> (next)
'done
But when I tried it my own in DrRacket, it came up with an error
> (+ 10 (-< 1 2 3))
. . -<: undefined;
cannot reference an identifier before its definition
>
The slide didn't indicate any requirement. I also google "racket -<: undefined", but seems google can't find any result relate to the symbol -<. How can I fix it?
racket
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
I see this in the lecture slide
> (+ 10 (-< 1 2 3))
11
> (next)
12
> (next)
13
> (next)
'done
But when I tried it my own in DrRacket, it came up with an error
> (+ 10 (-< 1 2 3))
. . -<: undefined;
cannot reference an identifier before its definition
>
The slide didn't indicate any requirement. I also google "racket -<: undefined", but seems google can't find any result relate to the symbol -<. How can I fix it?
racket
racket
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
asked Nov 14 '18 at 0:42
user8314628user8314628
579210
579210
3
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29
add a comment |
3
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29
3
3
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29
add a comment |
1 Answer
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Based on the link to the slides that you posted, it appears that the -< form is defined as a macro (using syntax-rules) on slide 19/48. After you add that macro definition to your program, you should be able to use the -< form.
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
add a comment |
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Based on the link to the slides that you posted, it appears that the -< form is defined as a macro (using syntax-rules) on slide 19/48. After you add that macro definition to your program, you should be able to use the -< form.
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
add a comment |
Based on the link to the slides that you posted, it appears that the -< form is defined as a macro (using syntax-rules) on slide 19/48. After you add that macro definition to your program, you should be able to use the -< form.
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
add a comment |
Based on the link to the slides that you posted, it appears that the -< form is defined as a macro (using syntax-rules) on slide 19/48. After you add that macro definition to your program, you should be able to use the -< form.
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
Based on the link to the slides that you posted, it appears that the -< form is defined as a macro (using syntax-rules) on slide 19/48. After you add that macro definition to your program, you should be able to use the -< form.
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
answered Nov 24 '18 at 19:44
John ClementsJohn Clements
13.9k32336
13.9k32336
add a comment |
add a comment |
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3
I think you're going to have to tell us whose lecture :). It looks like the amb operator that your instructor is using creates a re-entrant generator using continuations, but to tell you more, you'll have to give us more details. Put differently: it isn't hard to implement something like what you've described, but AFAICT, it's not part of a standard built-in library.
– John Clements
Nov 14 '18 at 2:58
Sorry, I didn't see ur comment. Here is the lecture slide. mcs.utm.utoronto.ca/~324/lec/lec07/slides07.pdf
– user8314628
Nov 20 '18 at 6:29