Assignment by Value

We use the "=" sign to imply the assignment by value. It makes a new copy of the object in memory and assigns it to the new variable.

Syntax

For variables:

<variable>[index]=<object>

For constant variables:

const <variable>=<object>

Examples

y=6 4 7
// output
[6,4,7]

x=y;
x;
// output
[6,4,7]
y[1]=0;
// output
[6,0,7]
x;
// output
[6,4,7]
// modifying y does does not affect x

const a=10;

Release an object: <variable>=NULL or use the undef command. Sometimes, to reduce the footprint of an application, we would like to release some variables from the system memory.

x=6 4 7;
x;
// output
[6,4,7]
x=NULL;
x;
// output
NULL


x=6 4 7;
undef(`x, VAR);
x;
// output
Syntax Error: [line #1] Cannot recognize the token x

DolphinDB also supports the following assignment operators: +=, -=, *=, /= and =.

x=0;
x+=5;
x;
// output
5
// equivalent to x=x+5

x=5;
x-=2;
x;
// output
3
// equivalent to x = x - 2

x=5
x*=5;
x;
// output
25
// equivalent to  x = x * 5

x=5;
x/=2;
x;
// output
2
// equivalent to  x = x / 5.

x=5;
x\=2;
x;
// output
2.5

x=1 2 3 4 5;
x[1 3]+=10;

x;
// output
[1,12,3,14,5]