[NOTE: at  09/09/2020 the functionality became available & built-in for PineScript for several functions]

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[Original Article]

Probably, you have already met the problem, when you tried to use highest()  or lowest() functions in TradingView PineScript using the dynamic/calculated variable, i.e.:

length = close > open ? 2 : 3
my_value = highest(close, length )

So, you will get the error:

Cannot call `highest` with arguments (series, series); available overloads: highest(series, integer) => series; highest(integer) => series;
Cannot call `lowest` with arguments (series, series); available overloads: lowest(series, integer) => series; lowest(integer) => series;
Cannot call `rising` with arguments (series, series); available overloads: lowest(series, integer) => series; lowest(integer) => series;
Cannot call `falling` with arguments (series, series); available overloads: lowest(series, integer) => series; lowest(integer) => series;

As always (this is generic rule in most platforms), the platform developers just ignore users’ requests for years, even for simple things (So, don’t hope your request-topic, opened years ago, will be ever fixed in near future). Instead, you should find a custom solution. So, we had to create a custom solution for that, and finally did:

highest / lowest:

highest_(values, length) =>
	h_val = values[0]
	h_indx = 0
	if length >= 1
		for i = 0 to length-1
			if ( not na(values[i]) and values[i] > h_val  )
				h_indx := i
				h_val := values[i]
	h_val
	
lowest_(values, length) =>
	l_val = values[0]
	l_indx = 0
	if length >= 1
		for i = 0 to length-1
			if ( not na(values[i]) and values[i] < l_val )
				l_indx := i
				l_val := values[i]
	l_val

You can use now:

hVal = highest_(high, length)

 

falling / rising:

rising_(values, length) =>
	current_ = values[0]
	ok_ = false
	if length>0 and length<=bar_index
	    ok_ := true
		for i = 1 to length
			if ( not na(values[i]) and current_ <= values[i] )
				ok_ := false
				break
	ok_


falling_(values, length) =>
	current_ = values[0]
	ok_ = false
	if length>0 and length<=bar_index
	    ok_ := true
		for i = 1 to length
			if ( not na(values[i]) and current_ >= values[i] )
				ok_ := false
				break
	ok_

You can use:

myVar = rising_(close, length)