How to identify a reserved word in a text file lexical analyzer

[Joemar P. Gava]

For identifying a digit isdigit()
For identifying a letter isalpha()

Now the problem is how do I identify if the input is a reserved word? It just read the word as a letter coz of the isalpha() function. Any idea? Thanks. I'll post some codes if needed.

[jimblumberg]

Read the word then compare that word with your list of reserved words?


Jim

[Joemar P. Gava]

Read the word then compare that word with your list of reserved words?


Jim

Where do I list the reserved words? Would an array will do? Coz when comparing it in a if statement of course it will not be accepted because it is a reserved word.

for an instance in a for loop:

if (lexeme[i] == "for")
{
     statements....
}

in error will occur...

[laserlight]

Where do I list the reserved words? Would an array will do?

Yes, an array might work.

Coz when comparing it in a if statement of course it will not be accepted because it is a reserved word.

That does not make sense. When you ask "how to identify a reserved word in a text file lexical analyzer", the term "reserved word" has to do which whatever the lexical analyser will be analysing. This has nothing to do with the reserved words of C, unless you happen to be writing a lexical analyser for C.

for an instance in a for loop:

if (lexeme[i] == "for")
{
     statements....
}

in error will occur...

Rubbish. Have you actually tried to compile your code? There is a mistake, but it is not an error that will prevent you from compiling the code. The mistake is that you used operator == to compare two strings, but this will result in pointer comparison, whereas you should be using strcmp or something similiar to compare the strings.

Perhaps you are thinking that because for is a reserved identifier in C, there will be a problem. Nope, there is no problem because "for" is a string literal, not an identifier, so the fact that for is a reserved identifier is not relevant.