Introduction

Jamie Zawinski:

Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.

It's so many regular expression forms are difficult to understand, such as perl, python, grep awk

Rob Pike's talk also point out some disadvantage about regular expressions, He said it more easy write it in go for pragrammer than use regular expression.

Regular expression in Math definition:

• a single charater is regular expression
• concat: if R1 ,R2 are regular expression, R1 concat R2 are also regular expression
• select: if R1 ,R2 are regular expression, R1 | R2 are also regular expression
• repeat : R1 repeat concat R1 ,the result is also regular expression This project rewrite regular-expression-in-hy in go . It just offer three type basic function, Concat_fn, Select_fn, Repeate_fn and return tuple like matched, readString, restString ,matched is show whether string matched the pattern, readString show that string has matched, rest part is restString.

Samples

var MatchSpace_fn Bool_string_string_fn = func(x string) (bool, string, string) {
	return Match_fn(x, func(in string) bool {
		return in == " "
	})
} // MatchSpace_fn

var MatchTab_fn = func(x string) (bool, string, string) {
	return Match_fn(x, func(in string) bool {
		return in == "\t"
	})
} // match_tab

var Match_alpha_fn = func(x string) (bool, string, string) {
	return Match_fn(x, func(in string) bool {
		return in >= "a" && in <= "z" || in >= "A" && in <= "Z"
	})
}
var Match_digit_fn = func(x string) (bool, string, string) {
	return Match_fn(x, func(in string) bool {
		return in >= "0" && in <= "9"
	})
}

var blank_fn Bool_string_string_fn = Repeat_fn(Select_fn(MatchSpace_fn, MatchTab_fn), 1, MaxInt)

// alhpabet apha_digit repeat 0~MAX
var identifer_fn Bool_string_string_fn = Concat_fn(
	Match_alpha_fn,
	Repeat_fn(Select_fn(
		Match_alpha_fn, Match_digit_fn), 0, MaxInt),
)

Useage:

flag, read, rest := identifer_fn("a12q123_")	if flag != true {
		t.Errorf("identifer failed")
} else {
	fmt.Println("match:", read)
	fmt.Println("rest:", rest)
}

LICENSE

MIT