When using solve to <return> a single variable

hhtt

Senior Member
Turkish
Hi, Because I am a student, it is important to understand textbooks for me. So I want to ask you a question about the verb of return in this example sentence: "When using solve to return a single variable, the array syntax is not necessary." The source is the book Matlab Demystified. Can someone explain me please what does it mean by
"to return a single variable" and here "solve" is a command.

Best Regards.
 
  • entangledbank

    Senior Member
    English - South-East England
    A function returns a value. If sqr() calculates squares, and you put 8 in, the function call sqr(8) returns the value 64 - you give it the value 8, and it then gives you the value 64, which is called the return value. A function that solves an equation might need to return one value or more than one. So x - 2 = 0 has only one answer, but (x - 2)(x + 3) = 0 has two answers, and a cubic has three answers, and so on. So in general the solve() function needs to return an array of values: such as [2, -3] or [2, -3, -7]. But if it returns only one value (a single variable), it doesn't have to return the one-value array [2]. It can just return the one variable value 2. The value 2 is just a number, but the array [2] uses array syntax.
     

    hhtt

    Senior Member
    Turkish
    But here the usage is a little different. Can you explain it? "MATLAB will simply return the command prompt and won’t say anything else,but if you try to use these variables again without assigning them values it will be as if they had not been seen before." So what does it mean
    by return the command prompt.
     
    Last edited:

    Andygc

    Senior Member
    British English
    Are you sure you copied that correctly? Not "MATLAB will simply return to the command prompt ..." A mathematical function cannot return the command prompt, the prompt isn't a value.
     

    Myridon

    Senior Member
    English - US
    In command line mode, you are given a command prompt:
    >
    you type
    > sqr(8)
    and Matlab returns:
    64
    >
    It "returns" the result and puts up a new command prompt. In this case, you type some gibberish and it give you no answer but it does give you a command prompt.
    You type:
    > gibberish
    MATLAB returns:
    >
     

    hhtt

    Senior Member
    Turkish
    In command line mode, you are given a command prompt:
    >
    you type
    > sqr(8)
    and Matlab returns:
    64
    >
    It "returns" the result and puts up a new command prompt. In this case, you type some gibberish and it give you no answer but it does give you a command prompt.
    You type:
    > gibberish
    MATLAB returns:
    >
    Hi, Myridon. What do you mean by gibberish? If I write it(gibberish) to the command prompt Matlab do not recognize it. Can you expand that example please. And thank you
    for Matlab course.
     

    Andygc

    Senior Member
    British English
    Context would help. We don't know what comes before "MATLAB will simply return the command prompt and won’t say anything else,but if you try to use these variables again without assigning them values it will be as if they had not been seen before."
     

    Judica

    Senior Member
    AE (US), Spanish (LatAm)
    Hi, Myridon. What do you mean by gibberish? If I write it(gibberish) to the command prompt Matlab do not recognize it. Can you expand that example please. And thank you
    for Matlab course.
    "Gibberish" means anything that makes no sense. (see a dictionary)

    MATLAB takes mathematical values, if you put in "tank", a word, you will get a command prompt because there is no mathematical value for MATLAB to compute.

    Myridon's explanation is spot on.
     

    hhtt

    Senior Member
    Turkish
    Namely, If we write some gibberish things on matlab command prompt it returns them to command prompt. Is it true?
     

    Andygc

    Senior Member
    British English
    Myridon's explanation is spot on.
    As an explanation of what happens, but not of the phrase "return the command prompt". MATLAB may well return a null value following an input error (which won't, of course, display on the screen), but it can't return the prompt. It returns to the command prompt after every transaction, whatever value it returns, but that is a different meaning of 'return' from the original question about 'return a variable'. Remember this is supposed to be a discussion of the meaning and use of words, not of a computer program.
     

    Myridon

    Senior Member
    English - US
    You didn't give us enough context to really answer the question. I mean "whatever action that the book is talking about before the sentence you gave in post #3". I was just making an guess that it might be typing something that the program doesn't understand.
     
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