To "assign" a variable means to symbolically associate a specific piece of information with a name. Any operations that are applied to this "name" (or variable) must hold true for any possible values. The assignment operator is the equals sign which SHOULD NEVER be used for equality, which is the double equals sign.
The '=' symbol is the assignment operator. Warning, while the assignment operator looks like the traditional mathematical equals sign, this is NOT the case. The equals operator is '=='
variable_name = expression; // Expression could be a number: variable_name = 5; // or a math expression: variable_name = 10 + 5 / 3 - 7; // or a funciton call : variable_name = sin( 5 );
To evaluate an assignment statement:
We've already seen many examples of assignment. Assignment means: "storing a value (of a particular type) under a variable name". Think of each assignment as copying the value of the righthand side of the expression into a "bucket" associated with the left hand side name!
Read this as, the variable called "name" is "assigned" the value computed by the expression to the right of the assignment operator ('=');
jims_age = 51; % first time we say that we have declared the variable jims_age = 21; % second time. we are changing the value that is associated with the variable daves_age = jims_age; % evaluate jims_age, get 21, then assign 21 to daves_age jims_age = 19; % what is daves_age?
Now that you have seen some variables being assigned, tell me what the following code means?
% PATTERN MATCHING lkjasdlfjlskdfjlksjdflkj = jlkajdsf + lkjsdflkjsdf; % what does this mean?
The answer to above questions: the assignment means that lkjasdlfjlskdfjlksjdflkj is a variable (a really badly named one), but a variable none-the-less. jlkajdsf and lkjsdflkjsdf must also be variables. The sum of the two numbers held in jlkajdsf and lkjsdflkjsdf is stored in the variable lkjasdlfjlskdfjlksjdflkj.
realmin % the smallest possible positive number greater than 0 pi % the value of pi eps % the smallest "GAP" between two numbers that the computer % can recognize (anything smaller and the computer % thinks the numbers are the same). inf % Infinity (biggest number) NaN % Not a Number (something wrong has happened; 0 divided by 0)
For more info, use the "help" command: (e.g., help realmin);
wage_per_hour = 25.40; % dollars per hour wage_per_hour = 12.00; % dollars per hour changed (for rest of program has new value) hours_worked_per_day = 8.0; % eight hour work day hours_worked_per_week = hours_worked_per_week * 5; % five days per week weekly_wage = hours_worked_per_week * wage_per_hour; yearly_wage = ???; % assume 52 work weeks in a year fprintf("I made %f dollars this year\n", yearly_wage);
The assignment pattern creates a new variable, if this is the first time we have seen the "name", or, updates the variable to a new value!
Read the following code in English as: First, compute the value of the thing to the right of the assignment operator (the =). then store the computed value under the given name, destroying anything that was there before.
Or more concisely: assign the variable "name" the value computed by "right_hand_expression"
name = right_hand_expression; % this DEFINES or updates a variable. % The right_hand_expression could be many things:. % Another Variable . % A Math Expression. % A Function Call.