Swapping Variables by pattern matching?
Assume you have 2 Integer Variables a and b
How would you swap them only if a > b by using a match expression?
If a <= b do not swap the ints.
In an imperative language:
if (a > b){
int temp=a;
a=b;
b=temp;
}
Doing the same in ocaml seems surprisingly hard.
I tried
let swap a b =
match a,b with
| a,b when a > b -> b,a
| a,b when a <= b -> a,b
I am trying to do this because in the following function call, I want to make sure that x is the bigger of the two variables.
functional-programming ocaml
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
add a comment |
Assume you have 2 Integer Variables a and b
How would you swap them only if a > b by using a match expression?
If a <= b do not swap the ints.
In an imperative language:
if (a > b){
int temp=a;
a=b;
b=temp;
}
Doing the same in ocaml seems surprisingly hard.
I tried
let swap a b =
match a,b with
| a,b when a > b -> b,a
| a,b when a <= b -> a,b
I am trying to do this because in the following function call, I want to make sure that x is the bigger of the two variables.
functional-programming ocaml
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
add a comment |
Assume you have 2 Integer Variables a and b
How would you swap them only if a > b by using a match expression?
If a <= b do not swap the ints.
In an imperative language:
if (a > b){
int temp=a;
a=b;
b=temp;
}
Doing the same in ocaml seems surprisingly hard.
I tried
let swap a b =
match a,b with
| a,b when a > b -> b,a
| a,b when a <= b -> a,b
I am trying to do this because in the following function call, I want to make sure that x is the bigger of the two variables.
functional-programming ocaml
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
Assume you have 2 Integer Variables a and b
How would you swap them only if a > b by using a match expression?
If a <= b do not swap the ints.
In an imperative language:
if (a > b){
int temp=a;
a=b;
b=temp;
}
Doing the same in ocaml seems surprisingly hard.
I tried
let swap a b =
match a,b with
| a,b when a > b -> b,a
| a,b when a <= b -> a,b
I am trying to do this because in the following function call, I want to make sure that x is the bigger of the two variables.
functional-programming ocaml
functional-programming ocaml
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
edited Nov 22 '18 at 13:04
chubbseN
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
asked Nov 22 '18 at 12:57
chubbseNchubbseN
184
184
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
Without state, you cannot "swap" the values of the variables since the variables are immutable. Your best bet is to use a tuple and introduce new variables in the scope. Example:
let diff a b =
let (min, max) = if a <= b then (a, b) else (b, a)
in max - min
You can of course use the same identifiers and shadow the original variables:
let diff a b =
let (a, b) = if a <= b then (a, b) else (b, a)
in b - a
It doesn't really help with readability though.
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
add a comment |
One easy way :
let swap a b =
if (a>b) then (b,a)
else (a,b)
But this is not equivalent to the C code, your C code is swapping the value of the variable - this is how imperative language are doing.
In Ocaml, there is no side-effect (except if you use reference to some int). This swap function will return a tuple whose members are always ordered (the first member will be always smaller than the second order).
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
add a comment |
Just for reference, if you'd like to swap the values in two refs, it would look like the following:
let swap a_ref b_ref =
let a, b = !a_ref, !b_ref in
a_ref := b;
b_ref := a
;;
which has the type val swap : 'a ref -> 'a ref -> unit.
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
Without state, you cannot "swap" the values of the variables since the variables are immutable. Your best bet is to use a tuple and introduce new variables in the scope. Example:
let diff a b =
let (min, max) = if a <= b then (a, b) else (b, a)
in max - min
You can of course use the same identifiers and shadow the original variables:
let diff a b =
let (a, b) = if a <= b then (a, b) else (b, a)
in b - a
It doesn't really help with readability though.
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
add a comment |
Without state, you cannot "swap" the values of the variables since the variables are immutable. Your best bet is to use a tuple and introduce new variables in the scope. Example:
let diff a b =
let (min, max) = if a <= b then (a, b) else (b, a)
in max - min
You can of course use the same identifiers and shadow the original variables:
let diff a b =
let (a, b) = if a <= b then (a, b) else (b, a)
in b - a
It doesn't really help with readability though.
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
add a comment |
Without state, you cannot "swap" the values of the variables since the variables are immutable. Your best bet is to use a tuple and introduce new variables in the scope. Example:
let diff a b =
let (min, max) = if a <= b then (a, b) else (b, a)
in max - min
You can of course use the same identifiers and shadow the original variables:
let diff a b =
let (a, b) = if a <= b then (a, b) else (b, a)
in b - a
It doesn't really help with readability though.
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
Without state, you cannot "swap" the values of the variables since the variables are immutable. Your best bet is to use a tuple and introduce new variables in the scope. Example:
let diff a b =
let (min, max) = if a <= b then (a, b) else (b, a)
in max - min
You can of course use the same identifiers and shadow the original variables:
let diff a b =
let (a, b) = if a <= b then (a, b) else (b, a)
in b - a
It doesn't really help with readability though.
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
answered Nov 22 '18 at 13:17
BergiBergi
366k58546872
366k58546872
add a comment |
add a comment |
One easy way :
let swap a b =
if (a>b) then (b,a)
else (a,b)
But this is not equivalent to the C code, your C code is swapping the value of the variable - this is how imperative language are doing.
In Ocaml, there is no side-effect (except if you use reference to some int). This swap function will return a tuple whose members are always ordered (the first member will be always smaller than the second order).
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
add a comment |
One easy way :
let swap a b =
if (a>b) then (b,a)
else (a,b)
But this is not equivalent to the C code, your C code is swapping the value of the variable - this is how imperative language are doing.
In Ocaml, there is no side-effect (except if you use reference to some int). This swap function will return a tuple whose members are always ordered (the first member will be always smaller than the second order).
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
add a comment |
One easy way :
let swap a b =
if (a>b) then (b,a)
else (a,b)
But this is not equivalent to the C code, your C code is swapping the value of the variable - this is how imperative language are doing.
In Ocaml, there is no side-effect (except if you use reference to some int). This swap function will return a tuple whose members are always ordered (the first member will be always smaller than the second order).
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
One easy way :
let swap a b =
if (a>b) then (b,a)
else (a,b)
But this is not equivalent to the C code, your C code is swapping the value of the variable - this is how imperative language are doing.
In Ocaml, there is no side-effect (except if you use reference to some int). This swap function will return a tuple whose members are always ordered (the first member will be always smaller than the second order).
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
answered Nov 22 '18 at 13:04
Pierre G.Pierre G.
3,3281721
3,3281721
add a comment |
add a comment |
Just for reference, if you'd like to swap the values in two refs, it would look like the following:
let swap a_ref b_ref =
let a, b = !a_ref, !b_ref in
a_ref := b;
b_ref := a
;;
which has the type val swap : 'a ref -> 'a ref -> unit.
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
add a comment |
Just for reference, if you'd like to swap the values in two refs, it would look like the following:
let swap a_ref b_ref =
let a, b = !a_ref, !b_ref in
a_ref := b;
b_ref := a
;;
which has the type val swap : 'a ref -> 'a ref -> unit.
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
add a comment |
Just for reference, if you'd like to swap the values in two refs, it would look like the following:
let swap a_ref b_ref =
let a, b = !a_ref, !b_ref in
a_ref := b;
b_ref := a
;;
which has the type val swap : 'a ref -> 'a ref -> unit.
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
Just for reference, if you'd like to swap the values in two refs, it would look like the following:
let swap a_ref b_ref =
let a, b = !a_ref, !b_ref in
a_ref := b;
b_ref := a
;;
which has the type val swap : 'a ref -> 'a ref -> unit.
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
answered Dec 1 '18 at 17:47
mc10mc10
8,44942851
8,44942851
add a comment |
add a comment |
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