How to eliminate leading zeros in a number?

Question

Hi I want to know how to eliminate leading zero's in a number using macros. for example if i give XX.XX then this means that any number can occupy X which will be sent by the application dynamically. if the application sends 1234 then the number i will showing is 12.34 where as if the application sends 12 then i should show 0.12 here i should eliminate the leading zero. similarly if i get 1 then the value should be 0.01. That means i should eliminate all the leading zero's before decimal point except the units decimal point. Which should be done using macro. if the macro is defined i should eliminate zero's if not i should not eliminate. If the value doesn't contain any decimal point like XXXX or XX or XXX or X what ever then i should eliminate all the leading zero's what ever the number may be. Note: i need pure C coding.

Vulpes · Answer

Well you can't do anything dynamically (i.e. at runtime) with macros as all they can do is replace text within the source code (albeit in some complex ways) at compile time. Why don't you use a C library function such as sprintf to format numbers?

Sean Stewart · Answer

http://www.robvanderwoude.com/battech_leadingzero.php

Sam Hobbs · Answer

What is the pupose of posting that code? Does it show the solution or do you have a question about it? If you have a question then what is the question about the code?

Karthik Agarwal · Answer

void hmi_gfx_mgr_decode_bit_format(UINT16 bit_format void * bit_format_ref HMI_CHAR concat_string[] void * text_data_vp) { UINT16 Size; UINT16 final_size = 0; UINT16 len; UINT8 replace_char = 0; UINT32 *temp; UINT32 *temp3; UINT16 radix = 0; HMI_CHAR static_string[MAX_TEXT_LENGTH] = {0}; HMI_CHAR DNV[9] = {0}; UINT8 *stat = (UINT8 *)bit_format_ref; UINT8 *dynamic_string = (UINT8 *)text_data_vp; UINT16 array_index = HMI_STRLEN(concat_string); if(bit_format == 0x02) { temp3 = (UINT32 *)&bit_format_ref; Size = *temp3 & 0x0F; final_size = Size; temp = (UINT32 *)&text_data_vp; for(len = 0; len { if(array_index { replace_char = (HMI_CHAR) ((*temp % 10) + 48); *temp = *temp/10; DNV[radix++] = replace_char; } else { break; } } Size = *temp3 & 0xF0; Size = Size >> 4; final_size = final_size + Size; temp = (UINT32 *)&text_data_vp; if(Size > 0) { if(array_index { DNV[radix++] = '.'; final_size++; } for(len = 0; len { if(array_index { replace_char = (HMI_CHAR) ((*temp % 10) + 48); *temp = *temp/10; #ifdef LEADING_ZEROS_REQUIRED DNV[radix++] = replace_char; #else if(len > 0) { if(replace_char != '0') { DNV[radix++] = replace_char; } } else if(len == 0) { DNV[radix++] = replace_char; } #endif } else { break; } } } for(len = final_size; len >= 0; len--) { concat_string[array_index++] = DNV[len]; if(len == 0) break; } }

Karthik Agarwal · Answer

To be precise i mean to say that before starting the application itself i will get to know whether i require leading zero's or not. So now if i require leading zero's i will define the macro if not i won't define based on this condition i want some code to implement this logic. What i meant about the dynamic data is i will be getting dynamic data from application side to the code which i wrote where i should be able to eliminate leading zero's based on the macro which i will be define based on my requirement. Of course i am finally putting them in the character array as i require that in the text format. To avoid your confusion please see the next post what i have already done.

Sam Hobbs · Answer

Let us put it this way. Do you need more than one version of your program (more than one exe file) each that works differently based on the macro's parameters or do you need one version of your program that works differently based on something that occurs during execution? The C and C++ compilers have something called the preprocessor. The preprocessor processes the #include statements the #define (macro) statements and all the statements that begin with a #. The preprocessor replaces those statements with other code. After all the preprocessor statements are gone then the compiler processes the source code. So all the source code beginning with # that the main compiler sees (after the preprocessor) including the macros are gone. The macros do not exist in the source code that the main compiler sees. It is impossible to use a macro during execution. So please read again what Vulpes said. Whatever it is that you are trying to say Application will send a number and if the macro is defined sound inconsistent with the way that macros work. Also note that leading zeros apply only to a number after conversion to text. The binary representation of a number will always have the same number of leading zeros. That is not entirely true if we consider 32-bit and 64-bit to be different but I hope you understand the point I am trying to make. The point I am making is that Vulpes suggests a C library function such as sprintf to format numbers because leading zeros is relevant to formatting numbers. The sprintf function and functions such as it use a format string and you can use one of multiple format strings depending on some condition.

Vulpes · Answer

For once I don't think I have misinterpreted what you meant. The point is that once the preprocessor has done its job the macro has gone and so can't be used to determine what action to take at runtime.

Karthik Agarwal · Answer

No Vulpes it looks like you mistook what i meant. Application will send a number to me at run time so then if the macro is defined i should not eliminate leading zero's and if not defined i should keep the zero's as it is.