匹配正则表达式时排除某些字符

Question

/[a-zA-Z]*/

The above matches all characters from az, but I would like to exclude when there is 'if' in the string.

Tried [^if] but couldn't accomplish what I was hoping for.

[EDIT] I have a formula evaluator which returns some value:

value = "if(a < b,a,b+1)"
formula = value.gsub(/[a-zA-Z]*/,'1')
verify = Calc.evaluate(formula)

I am trying to assign 1 to a and b inside the string and check if the formula is valid and evaluated.

Expected Output: "if(1 < 1,1,1+1)"

Answer 1

You can try this:

/((?!if )[a-zA-Z])*/

string = "abc"
string.match(/((?!if )[a-zA-Z])*/) 
# MatchData "abc"
string = "if abc" 
# MatchData ""

Answer 2

要得到想要的，可以使用gsub如下所示：

"if(a < b,a,b+1)".gsub(/[a-zA-Z]+/){|m| m == 'if' ? m : '1' }

Answer 3

I am trying to assign 1 to a and b inside the string...

Well, if you're trying to do that, then why are you messing with anything but a or b ?

str = 'if(a < b,a,b+1)'
str.gsub(/\b[ab]\b/, '1') # => "if(1 < 1,1,1+1)"

\\b is a word-boundary marker, so \\b[ab]\\b means a or b has to be an individual character.