### 3.3.2 Assigning values to variables

You can assign a value to a variable with the := operator. For example, to give the variable a the value of 4, enter:

a:=4

Alternatively, use the => operator; when you use this operator, the value comes before the variable:

4=>a

The function sto (or Store) can also be used; again, the value comes before the variable (the value is stored into the variable):

sto(4,a)

After any one of these commands, whenever you use the variable a in an expression, it will be replaced by 4.

use sequences or lists to make multiple assignments at the same time. For example,

(a,b,c):=(1,2,3)

will assign a the value 1, b the value 2 and c the value 3. Note that this can be used to swap the values of two variables; with a and b as above, the command

(a,b):=(b,a)

will set a equal to b’s original value, namely 2, and will set b equal to a’s original value, namely 1.

Another way to assign values to variables, useful in Maple mode, is with the assign command. If you enter

assign(a,3)

or

assign(a=3)

then a will have the value 3. You can assign multiple values at once; if you enter

assign([a=1,b=2])

then a will have the value 1 and b will have the value 2. This command can be useful in Maple mode, where solutions of equations are returned as equations. For example, if you enter (in Maple mode):

sol:=solve([x+y=1,y=2],[x,y])

(see Section 9.3.6), you will get

[x=−1,y=2] |  |  |  |  |  |  |  |  |  |

If you then enter

assign(sol)

the variable x will have value -1 and y will have the value 2. This same effect can be achieved in standard Xcas mode, where

sol:=solve([x+y=1,y=2],[x,y])

will return

| ⎡ ⎣ | ⎡ ⎣ | −1,2 | ⎤ ⎦ | ⎤ ⎦

In this case, the command

[x,y]:=sol[0]

will assign x the value -1 and y the value 2.