Are you using C++?

Because in

pidupdate=3D'"STRING_PREAMBLE"'+ID+','+posVal;console.log('pid
update:'+pidupdate)

The plus signs are not valid in C to concatenate strings, also, if posVal
is a variable then even without the plus signs it would not work.

In C you could write:

#define STRING_PREAMBLE @
#define STRINGIFY_(c) #c
#define STRINGIFY(c) STRINGIFY_(c)

Then:

char *pidupdate=3DSTRINGIFY(STRING_PREAMBLE) ID "," posVal;

I just noticed you are using single quotes for some elements of the
expression. I'm pretty sure you must be using C++.

C++ is not C. They have important differences.

Cheers,
Isaac



Em dom, 29 de set de 2019 05:03, Justin Richards <justin.richards@gmail.com=
>
escreveu:

> Using macros to make some code more readable and maintainable I always se=
em
> to hit snags.
>
> Struggling to define the question, I have used examples below to try and
> illustrate my query.
>
> I wanted to convert this
>
> if (payload[0] =3D=3D '@')
> {
>  ...
> }
>
> to
> #define STRING_PREAMBLE '@'
>
> if (payload[0] =3D=3D STRING_PREAMBLE)
> {
>  ...
> }
>
> The compiler complains with "expected ')' before '@'
>
> So i tried variations on the theme
> #define STRING_PREAMBLE @
> #define STRING_PREAMBLE "'@'"
> #define STRING_PREAMBLE "@"
>
> The later two variations compiles but the following comparison  fails
>    if (payload[0] =3D=3D 'STRING_PREAMBLE')
>
> The macro is used elsewhere in the code as part of a string of embedded
> HTML that embeds javascript and behaves as required
> "var
>
> pidupdate=3D'"STRING_PREAMBLE"'+ID+','+posVal;console.log('pidupdate:'+pi=
dupdate);"
>
> this was previously coded as
>
> "var pidupdate=3D'@'+ID+','+posVal;console.log('pidupdate:'+pidupdate);"
>
> Any hints or suggestions on how i should phrase my search.
>
> Justin
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