Common Lisp dotimes result mystery
I got this
(dotimes (temp-one 10 temp-one))
from the Hyperspec examples on dotimes. Running this produces the answer 10. So the temp-one in the third parameter position is acting as a returned "result," but how did it get to 10 when dotimes starts at 0 and would only go to 9?
>(dotimes (temp-one 10 temp-one) (format t "~3d " temp-one))
0 1 2 3 4 5 6 7 8 9
10
What am I missing here about the third parameter?
loops common-lisp
asked Nov 21 '18 at 5:28
147pm147pm
582416
add a comment |
I got this
(dotimes (temp-one 10 temp-one))
from the Hyperspec examples on dotimes. Running this produces the answer 10. So the temp-one in the third parameter position is acting as a returned "result," but how did it get to 10 when dotimes starts at 0 and would only go to 9?
>(dotimes (temp-one 10 temp-one) (format t "~3d " temp-one))
0 1 2 3 4 5 6 7 8 9
10
What am I missing here about the third parameter?
loops common-lisp
asked Nov 21 '18 at 5:28
147pm147pm
582416
3
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50
add a comment |
I got this
(dotimes (temp-one 10 temp-one))
from the Hyperspec examples on dotimes. Running this produces the answer 10. So the temp-one in the third parameter position is acting as a returned "result," but how did it get to 10 when dotimes starts at 0 and would only go to 9?
>(dotimes (temp-one 10 temp-one) (format t "~3d " temp-one))
0 1 2 3 4 5 6 7 8 9
10
What am I missing here about the third parameter?
loops common-lisp
asked Nov 21 '18 at 5:28
147pm147pm
582416
I got this
(dotimes (temp-one 10 temp-one))
from the Hyperspec examples on dotimes. Running this produces the answer 10. So the temp-one in the third parameter position is acting as a returned "result," but how did it get to 10 when dotimes starts at 0 and would only go to 9?
>(dotimes (temp-one 10 temp-one) (format t "~3d " temp-one))
0 1 2 3 4 5 6 7 8 9
10
What am I missing here about the third parameter?
loops common-lisp
loops common-lisp
asked Nov 21 '18 at 5:28
147pm147pm
582416
asked Nov 21 '18 at 5:28
147pm147pm
582416
asked Nov 21 '18 at 5:28
147pm147pm
582416
asked Nov 21 '18 at 5:28
147pm147pm
582416
asked Nov 21 '18 at 5:28
147pm147pm
582416
582416
3
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50
add a comment |
3
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50
3
3
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50
add a comment |
2 Answers
2
active
oldest
votes
If you look at the dotimes Hyperspec entry it states it's a macro meaning you get to see "under the hood" by calling macroexpand:
(macroexpand '(dotimes (i 10 i)))
SBCL:
(BLOCK NIL
(LET ((I 0))
(DECLARE (TYPE UNSIGNED-BYTE I))
(TAGBODY
(GO #:G386)
#:G385
(TAGBODY)
(PSETQ I (1+ I))
#:G386
(UNLESS (>= I 10) (GO #:G385))
(RETURN-FROM NIL (PROGN I)))))
Allegro CL:
(do ((i 0 (1+ i)))
((>= i 10) i))
In both cases the iteration variable i is increased by one, and then the end test (>= i 10) is done. As jkiiski wrote:
"At the time result-form is processed, var is bound to the number of times the body was executed."
and the (return-from ..) form (SBCL) and i form (Allegro CL) are evaluated after the variable increase and test.
answered Nov 21 '18 at 8:44
zutzut
55624
Right after I posted this I realized it had to be something like the last iteration is sent toresult-formeven though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.
– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding usingtagbodywithgoand labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.
– zut
Nov 22 '18 at 22:03
add a comment |
Hyperspec says:
At the time result-form is processed, var is bound to the number of
times the body was executed.
So, in the third form, the result-form, the variable gets first bound to the number of times the body was executed first, and then the third form is evaluated.
That is why the value of the variable is 10 and not the current value 9.
This is also visible, if you do
(macroexpand-1 '(dotimes (temp-one 3 temp-one) (format t "~3d~%" temp-one)))
;; resulting in CLISP in:
;; (DO ((TEMP-ONE 0 (1+ TEMP-ONE))) ((>= TEMP-ONE 10) TEMP-ONE)
;; (FORMAT T "~3d~%" TEMP-ONE)) ;
;; T
So finally, (1+ TEMP-ONE) is returned by the DO loop, to which DOTIMES expands to - as pointed out by @zut.
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
add a comment |
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If you look at the dotimes Hyperspec entry it states it's a macro meaning you get to see "under the hood" by calling macroexpand:
(macroexpand '(dotimes (i 10 i)))
SBCL:
(BLOCK NIL
(LET ((I 0))
(DECLARE (TYPE UNSIGNED-BYTE I))
(TAGBODY
(GO #:G386)
#:G385
(TAGBODY)
(PSETQ I (1+ I))
#:G386
(UNLESS (>= I 10) (GO #:G385))
(RETURN-FROM NIL (PROGN I)))))
Allegro CL:
(do ((i 0 (1+ i)))
((>= i 10) i))
In both cases the iteration variable i is increased by one, and then the end test (>= i 10) is done. As jkiiski wrote:
"At the time result-form is processed, var is bound to the number of times the body was executed."
and the (return-from ..) form (SBCL) and i form (Allegro CL) are evaluated after the variable increase and test.
answered Nov 21 '18 at 8:44
zutzut
55624
Right after I posted this I realized it had to be something like the last iteration is sent toresult-formeven though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.
– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding usingtagbodywithgoand labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.
– zut
Nov 22 '18 at 22:03
add a comment |
If you look at the dotimes Hyperspec entry it states it's a macro meaning you get to see "under the hood" by calling macroexpand:
(macroexpand '(dotimes (i 10 i)))
SBCL:
(BLOCK NIL
(LET ((I 0))
(DECLARE (TYPE UNSIGNED-BYTE I))
(TAGBODY
(GO #:G386)
#:G385
(TAGBODY)
(PSETQ I (1+ I))
#:G386
(UNLESS (>= I 10) (GO #:G385))
(RETURN-FROM NIL (PROGN I)))))
Allegro CL:
(do ((i 0 (1+ i)))
((>= i 10) i))
In both cases the iteration variable i is increased by one, and then the end test (>= i 10) is done. As jkiiski wrote:
"At the time result-form is processed, var is bound to the number of times the body was executed."
and the (return-from ..) form (SBCL) and i form (Allegro CL) are evaluated after the variable increase and test.
answered Nov 21 '18 at 8:44
zutzut
55624
Right after I posted this I realized it had to be something like the last iteration is sent toresult-formeven though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.
– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding usingtagbodywithgoand labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.
– zut
Nov 22 '18 at 22:03
add a comment |
If you look at the dotimes Hyperspec entry it states it's a macro meaning you get to see "under the hood" by calling macroexpand:
(macroexpand '(dotimes (i 10 i)))
SBCL:
(BLOCK NIL
(LET ((I 0))
(DECLARE (TYPE UNSIGNED-BYTE I))
(TAGBODY
(GO #:G386)
#:G385
(TAGBODY)
(PSETQ I (1+ I))
#:G386
(UNLESS (>= I 10) (GO #:G385))
(RETURN-FROM NIL (PROGN I)))))
Allegro CL:
(do ((i 0 (1+ i)))
((>= i 10) i))
In both cases the iteration variable i is increased by one, and then the end test (>= i 10) is done. As jkiiski wrote:
"At the time result-form is processed, var is bound to the number of times the body was executed."
and the (return-from ..) form (SBCL) and i form (Allegro CL) are evaluated after the variable increase and test.
answered Nov 21 '18 at 8:44
zutzut
55624
If you look at the dotimes Hyperspec entry it states it's a macro meaning you get to see "under the hood" by calling macroexpand:
(macroexpand '(dotimes (i 10 i)))
SBCL:
(BLOCK NIL
(LET ((I 0))
(DECLARE (TYPE UNSIGNED-BYTE I))
(TAGBODY
(GO #:G386)
#:G385
(TAGBODY)
(PSETQ I (1+ I))
#:G386
(UNLESS (>= I 10) (GO #:G385))
(RETURN-FROM NIL (PROGN I)))))
Allegro CL:
(do ((i 0 (1+ i)))
((>= i 10) i))
In both cases the iteration variable i is increased by one, and then the end test (>= i 10) is done. As jkiiski wrote:
"At the time result-form is processed, var is bound to the number of times the body was executed."
and the (return-from ..) form (SBCL) and i form (Allegro CL) are evaluated after the variable increase and test.
answered Nov 21 '18 at 8:44
zutzut
55624
answered Nov 21 '18 at 8:44
zutzut
55624
answered Nov 21 '18 at 8:44
zutzut
55624
answered Nov 21 '18 at 8:44
zutzut
55624
55624
Right after I posted this I realized it had to be something like the last iteration is sent toresult-formeven though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.
– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding usingtagbodywithgoand labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.
– zut
Nov 22 '18 at 22:03
add a comment |
Right after I posted this I realized it had to be something like the last iteration is sent toresult-formeven though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.
– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding usingtagbodywithgoand labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.
– zut
Nov 22 '18 at 22:03
Right after I posted this I realized it had to be something like the last iteration is sent to
result-form even though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.– 147pm
Nov 21 '18 at 17:08
Right after I posted this I realized it had to be something like the last iteration is sent to
result-form even though it fails/terminates. BTW, what sort of Lisp is that in the SBCL expanded macro? I'm still just a beginner and haven't seen much yet.– 147pm
Nov 21 '18 at 17:08
The macroexpansion given by SBCL, the
(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding using tagbody with go and labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.– zut
Nov 22 '18 at 22:03
The macroexpansion given by SBCL, the
(BLOCK NIL ..), is also Common Lisp. It's in upper case as that is the standard. (My Allegro example was done in its "Modern" mode that keeps case and uses lowercase for the standard functions; it also comes with "ANSI" mode that behaves like SBCL). Coding using tagbody with go and labels feels like low-level assembly code, usually you would use higher-level abstractions, but nevertheless it's all part of Common Lisp.– zut
Nov 22 '18 at 22:03
add a comment |
Hyperspec says:
At the time result-form is processed, var is bound to the number of
times the body was executed.
So, in the third form, the result-form, the variable gets first bound to the number of times the body was executed first, and then the third form is evaluated.
That is why the value of the variable is 10 and not the current value 9.
This is also visible, if you do
(macroexpand-1 '(dotimes (temp-one 3 temp-one) (format t "~3d~%" temp-one)))
;; resulting in CLISP in:
;; (DO ((TEMP-ONE 0 (1+ TEMP-ONE))) ((>= TEMP-ONE 10) TEMP-ONE)
;; (FORMAT T "~3d~%" TEMP-ONE)) ;
;; T
So finally, (1+ TEMP-ONE) is returned by the DO loop, to which DOTIMES expands to - as pointed out by @zut.
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
add a comment |
Hyperspec says:
At the time result-form is processed, var is bound to the number of
times the body was executed.
So, in the third form, the result-form, the variable gets first bound to the number of times the body was executed first, and then the third form is evaluated.
That is why the value of the variable is 10 and not the current value 9.
This is also visible, if you do
(macroexpand-1 '(dotimes (temp-one 3 temp-one) (format t "~3d~%" temp-one)))
;; resulting in CLISP in:
;; (DO ((TEMP-ONE 0 (1+ TEMP-ONE))) ((>= TEMP-ONE 10) TEMP-ONE)
;; (FORMAT T "~3d~%" TEMP-ONE)) ;
;; T
So finally, (1+ TEMP-ONE) is returned by the DO loop, to which DOTIMES expands to - as pointed out by @zut.
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
add a comment |
Hyperspec says:
At the time result-form is processed, var is bound to the number of
times the body was executed.
So, in the third form, the result-form, the variable gets first bound to the number of times the body was executed first, and then the third form is evaluated.
That is why the value of the variable is 10 and not the current value 9.
This is also visible, if you do
(macroexpand-1 '(dotimes (temp-one 3 temp-one) (format t "~3d~%" temp-one)))
;; resulting in CLISP in:
;; (DO ((TEMP-ONE 0 (1+ TEMP-ONE))) ((>= TEMP-ONE 10) TEMP-ONE)
;; (FORMAT T "~3d~%" TEMP-ONE)) ;
;; T
So finally, (1+ TEMP-ONE) is returned by the DO loop, to which DOTIMES expands to - as pointed out by @zut.
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
Hyperspec says:
At the time result-form is processed, var is bound to the number of
times the body was executed.
So, in the third form, the result-form, the variable gets first bound to the number of times the body was executed first, and then the third form is evaluated.
That is why the value of the variable is 10 and not the current value 9.
This is also visible, if you do
(macroexpand-1 '(dotimes (temp-one 3 temp-one) (format t "~3d~%" temp-one)))
;; resulting in CLISP in:
;; (DO ((TEMP-ONE 0 (1+ TEMP-ONE))) ((>= TEMP-ONE 10) TEMP-ONE)
;; (FORMAT T "~3d~%" TEMP-ONE)) ;
;; T
So finally, (1+ TEMP-ONE) is returned by the DO loop, to which DOTIMES expands to - as pointed out by @zut.
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
answered Nov 21 '18 at 11:09
Gwang-Jin KimGwang-Jin Kim
2,396116
2,396116
add a comment |
add a comment |
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3
As the hyperspec says: "At the time result-form is processed, var is bound to the number of times the body was executed"
– jkiiski
Nov 21 '18 at 5:50