Comment by bananaflag
3 months ago
I think the problem is that you don't get "syntax". What you think "syntax" is is actually semantics.
"Syntax" just means what strings are valid programs. For example, x=3 should be valid in C, while =+x shouldn't. Note that this doesn't say anything about what x=3 actually means in practice. The fact that there is a variable called x, and that it has a value at some point in time, and that after the execution of x=3 that value becomes 3 are all semantics.
> "Syntax" just means what strings are valid programs.
Strings are not objects in the syntactic domain, only terms are. And parsers operate on tokens, recognizing valid compositions of tokens (at least syntactically). Syntax concerns relations between tokens and thus their form and composition.
Semantics concerns the meanings of terms, where “meaning” is considered from various perspectives, like the denotational or operational (what the OP has in mind w.r.t. evaluation effectively concerns the denotational semantics). While computation is purely syntactic, denotational semantics is not circular, because the correspondence we assign (in our minds) to terms is with models that already possess a semantic content of their own.
There does exist a subtle middle ground between proper syntax and proper semantics, namely well-formedness. Well-formedness is technically a part of syntax rules (i.e. syntactic correctness) but not a part of formal grammars and other similar stuffs, making it harder to classify. For example, XML's opening tag and closing tag should be matched like <foo></foo>, but this syntactic rule is not described in the formal context-free grammar. It is possible to make a formal context-sensitive grammar that only accepts a well-formed syntax, but that would make the specification unnecessarily complex, hence the introduction of informal rules. Some still may argue that it is actually kind of semantics, however.
I think you misread what GP thinks syntax is. GP's definition
"whether the construct is allowed/part of the language (syntax)"
is the same as yours
""Syntax" just means what strings are valid programs"