Compiler/Verifying syntax: Difference between revisions

However, before applying the parser, we first need to ensure that the expressions don't include any characters (including non-ASCII) or usages thereof which Go would otherwise permit. Note that it's not necessary to specifically check for '"++'" and '"--'" as these are statements in Go and can't appear in expressions anyway.

In particular, after substitutions, '"= not'", "+ not" etc. would be allowed by the Go parser so we need to exclude itthem. Curiously, the Go parser allows something like '"2 < 3 < 4'" even though it doesn't compile. We need therefore to exclude that also (see Talk page).

<langsyntaxhighlight lang="go">package main

re1 = regexp.MustCompile(`[^_a-zA-Z0-9\+\-\*/=<\(\) \s]`)

re3 = regexp.MustCompile(`=[ =<+*/-]\s*not`)

re4 = regexp.MustCompile(`(=|<)[ ]\s*[^(=< ]+[ ]\s*([=|<+*/-])`)

return fmt.Errorf("expectedoperator EOF,%q foundis %qnon-associative", []rune(matches[21])[0])

}

}</langsyntaxhighlight>

"false" -> expected EOF, foundoperator '<' is non-associative

<langsyntaxhighlight lang="julia">function substituteinnerparentheses(s, subs)

# Julia allows expressions like 2 + + + 3, or like true = not false, but these are not allowed here

occursin(r"(^(and|^or|^[\=\<\+\-\*\/]))|((and|or|[\=\<\+\-\*\/])$)", s) ||

"235 76 + 1",

</langsyntaxhighlight>{{out}}

sub error { die s/\G/{{\U@_}}/r }

/\G (?!(?:and|or|not)\b) (?:\d+|[a-zA-Z]\w*)/gcgcx or

$level <= 2 && /\Gor\b/gc ? expr(23) :

$level <= 3 && /\Gand\b/gc ? expr(4) :

$level <= 4 && /\G[=<]/gc ? expr(4.5) :

$level == 4.5 && /\G(?=[=<])/gc ? error "operator is non-associative operator" :

$level <= 5 && /\G[+-]/gc ? expr(6) :

$level <= 6 && /\G[*\/]/gc ? expr(7) :

" true ${_}true\n" : "$@false\n", "\n $@";

l or _m</lang>

procedure // check validity of a primary()

or tt=INTEGER nextToken

next_token} else if (_token == Token.lpar) {

next_token if (!checkExpr) return false

or_expr if (_token != Token.rpar) {

tok = {ERROR,") expected"} return false

} else {

next_token() nextToken

end if return true

else }

tok} =else {ERROR,sprintok("invalid [%v]")}

whilecheckExpr6 true do{

primaryif (!checkPrimary) return false

next_token() nextToken

whilecheckExpr5 true do{

mul_exprif (!checkExpr6) return false

next_token() nextToken

sum_exprif (!checkExpr5) return false

next_token() nextToken

whilecheckExpr3 true do{

cmp_exprif (!checkExpr4) return false

ifwhile (_token tok!={IDENT,"= Token.and"}) then exit end if{

next_token() nextToken

whilecheckExpr2 true do{

and_exprif (!checkExpr3) return false

ifwhile (_token tok!={IDENT,"= Token.or"}) then exit end if{

next_token() nextToken

"if and(result 3&& _pos < 2",_len) {

_error = "notExtra characters at 7end <of 2statement.",

"4 * (32 - 16) + 9result = 73",false

"235 76 + 1",}

"areturn + b = not c and false",result

"l or _mwombat"},