sqrt() function help

This is a discussion on sqrt() function help within the C Programming forums, part of the General Programming Boards category; hey, i'm curious as to how you would go about passing a variable to the sqrt() function to get the ...

  1. #1
    Shibby willc0de4food's Avatar
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    sqrt() function help

    hey, i'm curious as to how you would go about passing a variable to the sqrt() function to get the square root of it. i've found that you can directly input a number to it, but when i try something like:
    Code:
    square_root = sqrt(user_number);
    i get:
    [tim@shibby documents]$ gcc -o SqRt sqrt.c
    /tmp/ccuCIkhZ.o(.text+0x82): In function `main':
    : undefined reference to `sqrt'
    collect2: ld returned 1 exit status

    so how can i do this? is there a better way? thanks
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    Quote Originally Posted by willc0de4food
    hey, i'm curious as to how you would go about passing a variable to the sqrt() function to get the square root of it. i've found that you can directly input a number to it, but when i try something like:
    Code:
    square_root = sqrt(user_number);
    i get:
    [tim@shibby documents]$ gcc -o SqRt sqrt.c
    /tmp/ccuCIkhZ.o(.text+0x82): In function `main':
    : undefined reference to `sqrt'
    collect2: ld returned 1 exit status

    so how can i do this? is there a better way? thanks

    Oki as I dont have your full code I will try to figure out what is wrong. Are you incluiding the #<math.h> header?

  3. #3
    Slave MadCow257's Avatar
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    Without the full code I can't know, but I belive that error would most likely come from the lack of the math.h header.
    Add
    #include <math.h>
    to the top of your code if you don't have it already

  4. #4
    Obsessed with C chrismiceli's Avatar
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    You have to link with the math library.
    gcc -o blah blah.c -lm
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  5. #5
    Shibby willc0de4food's Avatar
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    yea, i included the math.h header and i also tried including the tgmath.h header b/c i was unsure about which one to include and neither worked.

    but chrismiceli adding -lm worked thanks. but can you tell me what that does?
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  6. #6
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    Quote Originally Posted by willc0de4food
    yea, i included the math.h header and i also tried including the tgmath.h header b/c i was unsure about which one to include and neither worked.

    but chrismiceli adding -lm worked thanks. but can you tell me what that does?
    It is linking the library, take a look here -> http://developer.apple.com/documenta...libtool_3.html
    maybe no the best site for the topic but surely explains what you need.

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