Assignment Operations: Difference between revisions
m (moved Assignment Operators to Assignment Operations) |
(edit) |
||
| Line 3: | Line 3: | ||
They are similar in how they work with a slight difference. | They are similar in how they work with a slight difference. | ||
Both of them are [[Binary operations]], which means they take two arguments - one on the left, and another one on the right. | Both of them are [[Binary operations]], which means they take two arguments - one on the left side of the operator, and another one on the right. | ||
[[Numeric]] and [[String]] [[Variable|variables]] both may be used with regular and forced assignment operations. | [[Numeric]] and [[String]] [[Variable|variables]] both may be used with regular and forced assignment operations. | ||
| Line 16: | Line 16: | ||
00010 let 5 = x ! incorrect | 00010 let 5 = x ! incorrect | ||
===Forced Assignment=== | ===Forced Assignment=== | ||
The example below forced-assigns the value of 5 to x and then compares the value of x (which is now 5) to the value of 2: | |||
00010 if (x:=5) > 2 then print "The forced-assigned value is larger than 2" | 00010 if (x:=5) > 2 then print "The forced-assigned value is larger than 2" | ||
Revision as of 08:33, 11 January 2012
There are two assignment operations in BR: the equal sign =, which denotes regular assignment, and the colon-equal sign :=, which denotes forced assignment,
They are similar in how they work with a slight difference.
Both of them are Binary operations, which means they take two arguments - one on the left side of the operator, and another one on the right.
Numeric and String variables both may be used with regular and forced assignment operations.
Regular Assignment
The equal sign = simply makes the variable on the left side of it equal to the value on the right side of it. The example below assigns the value of 5 to the variable x:
00010 let x = 5 ! correct
Note that you cannot do the reverse. The example below will result in an error.
00010 let 5 = x ! incorrect
Forced Assignment
The example below forced-assigns the value of 5 to x and then compares the value of x (which is now 5) to the value of 2:
00010 if (x:=5) > 2 then print "The forced-assigned value is larger than 2"
Note that when this assignment operation is used in any expression (for example: in the condition of an IF THEN statement), parentheses must be used to clarify the order of execution Otherwise, unexpected results may occur.
IMPORTANT NOTE: when the equal sign is used in an If statement, it is NOT used for assignment. Instead, it is used for comparison. Consider the example below:
00010 let x = 1 ! assignment takes place 00020 let y = 1000 ! assignment takes place 00030 if x = y then print "1 is equal to 1000" ! assignment DOES NOT takes place
In the above example, assignment DOES NOT takes place, instead the IF statement evaluates to FALSE and the print statement DOES NOT execute.
IMPORTANT NOTE: when the equal sign is used in an If statement, it is equivalent to using two equal signs ==. So the above example is identical in effect to the one below:
00010 let x = 1 ! assignment takes place 00020 let y = 1000 ! assignment takes place 00030 if x == y then print "1 is equal to 1000" ! assignment DOES NOT takes place
For clarity, it may be better to use == for comparison.
IMPORTANT NOTE: when the forced assignment operation := is used in an If statement, it is used for forced assignment, not for comparison. Consider the example below:
00010 let x = 1 00020 if x:=2 then print "forced assignment as a condition of an if statement always evaluates to true"