# String function Problems **URL:** \ **Category:** Open AT\ **Created:** [July 17, 2009, 11:53pm UTC](https://forum.sierrawireless.com/t/string-function-problems/3456 "2009-07-17T23:53:35Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![MLCarter](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@MLCarter](https://forum.sierrawireless.com/u/MLCarter)\ **Post date:** [July 17, 2009, 11:53pm UTC](https://forum.sierrawireless.com/t/string-function-problems/3456/1 "2009-07-17T23:53:35Z")
Hello, I’m getting there with my C++ but just having problems cutting characters of an array. ```auto static ascii gpsbuff [DATA_MAX];//global //local u8 i,j,field,startp,len; ascii temp15[15]; temp15==strncpy(&gpsbuff[startp],temp15,len); temp15==strcat(temp15,"\r\n"); adl_atSendResponse ( ADL_AT_UNS, temp15 ); ``` output should be; 0 00 99.9 I get 9 9 9 9 I have to say I’m not clear on where to use the variable and where to use a pointer in these functions Help Please ---
**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\ **Post date:** [July 18, 2009, 7:48am UTC](https://forum.sierrawireless.com/t/string-function-problems/3456/2 "2009-07-18T07:48:26Z")
> [@MLCarter](#): > > I’m getting there with my C++ Actually, what you’ve shown is all just good ol’ C - it hasn’t strayed into any C++ territory (yet)… > [@](#): > > I have to say I’m not clear on where to use the variable and where to use a pointer For that, you need a ‘C’ textbook! You could start with [publications.gbdirect.co.uk/c\_book/](http://publications.gbdirect.co.uk/c_book/) Note that a pointer is a variable - the value of a pointer variable is the address of something and, because it’s a variable, you can change that value at run time; ie, you can assign a new value to it. The name of an array acts, in many ways, like a pointer - because it gives the address of the 1st element of the array - but the key difference is that you cannot assign a value to it. Its value is fixed at build time. Also note that “==” is not the assignment operator in ‘C’ ! The “==” double-equals is a comparison operator that checks if its two operands are equal! Thus this code contains two mistakes: ```auto temp15==strncpy(&gpsbuff[startp],temp15,len); // This is not an assignment, and would be illegal as an assignment! ``` 1. You are trying to assign to an array name - which is not allowed; 2. You are using the equality comparison operator (==) instead of the assignment operator (=) ---
**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\ **Post date:** [July 18, 2009, 7:53am UTC](https://forum.sierrawireless.com/t/string-function-problems/3456/3 "2009-07-18T07:53:29Z")
```auto temp15 == strncpy( &gpsbuff[startp], temp15, len ); ``` Once you’ve corrected the errors noted above, I think you also need to check carefully that you have the parameters to strncpy in the correct order for your required result… BTW: a little whitespace goes a long way in making code more readable… ---
**Author:** ![MLCarter](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@MLCarter](https://forum.sierrawireless.com/u/MLCarter)\ **Post date:** [July 18, 2009, 11:00pm UTC](https://forum.sierrawireless.com/t/string-function-problems/3456/4 "2009-07-18T23:00:40Z")
Thanks for the help. yes 😊 on the == I’m still struggling with basics, can’t find things in the documentation. Please for definations what is a s32? I asummed it was a 32bit single but it looks like 32 bit integer?? for single/double precision numbers it should be float number; double number; Also how do you TRACE output a floating point numbers? It seems that the standard %f is not available, %d should give 1 decimal place? number=9.98; TRACE((1,“number %d”,number)); gives Number 1076098498 One more how do convert string to float? e.g temp15=“9.98” ---
**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\ **Post date:** [July 18, 2009, 11:35pm UTC](https://forum.sierrawireless.com/t/string-function-problems/3456/5 "2009-07-18T23:35:51Z")
> [@MLCarter](#): > > I’m still struggling with basics It isn’t the place of the Wavecom documentation to teach you the ‘C’ language - it is assumed that you are already a competent ‘C’ programmer. > [@](#): > > what is a s32? I asummed it was a 32bit single but it looks like 32 bit integer?? Yes, it is a signed 32-bit integer And u32 is an unsigned 32-bit integer. Similarly for u16/s16 and u8/s8 But you’re right - they are not documented 😠 I guess they used to be documented in the so-called “Basic (sic) Development Guide” - now discontinued - and Wavecom forgot to put them into the ADL User Guide when the Basic guide was discontinued… 😒 See: [viewtopic.php?f=3&t=3692&p=14287#p14284](http://www.wavecom.com/modules/movie/scenes/forums/viewtopic.php?f=3&t=3692&p=14287#p14284) But you can see the definitions in wm\_types.h > [@](#): > > Also how do you TRACE output a floating point numbers? It seems that the standard %f is not available The problem with %f is documented - and a workaround is given. > [@](#): > > %d should give 1 decimal place? No - %d gives an integer (‘C’ textbook again)