Click

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Click is an open source programming language created in 1999.

Source code:

git clone https://github.com/kohler/click

#216on PLDB

25Years Old

39Repos

The Click modular router: fast modular packet processing and analysis

Click website
Click is developed on GitHub and has 667 stars
Click docs
There are at least 39 Click repos on GitHub
Click first developed in Massachusetts Institute of Technology
file extensions for Click include click
The Google BigQuery Public Dataset GitHub snapshot shows 115 users using Click in 127 repos on GitHub
GitHub supports syntax highlighting for Click

Example from Linguist:

rates :: AvailableRates
elementclass sr2 {
  $sr2_ip, $sr2_nm, $wireless_mac, $gateway, $probes|


arp :: ARPTable();
lt :: LinkTable(IP $sr2_ip);


gw :: SR2GatewaySelector(ETHTYPE 0x062c,
		      IP $sr2_ip,
		      ETH $wireless_mac,
		      LT lt,
		      ARP arp,
		      PERIOD 15,
		      GW $gateway);


gw -> SR2SetChecksum -> [0] output;

set_gw :: SR2SetGateway(SEL gw);


es :: SR2ETTStat(ETHTYPE 0x0641, 
	      ETH $wireless_mac, 
	      IP $sr2_ip, 
	      PERIOD 30000,
	      TAU 300000,
	      ARP arp,
	      PROBES $probes,
	      ETT metric,
	      RT rates);


metric :: SR2ETTMetric(LT lt);


forwarder :: SR2Forwarder(ETHTYPE 0x0643, 
			      IP $sr2_ip, 
			      ETH $wireless_mac, 
			      ARP arp, 
			      LT lt);


querier :: SR2Querier(ETH $wireless_mac, 
		     SR forwarder,
		     LT lt, 
		     ROUTE_DAMPENING true,
		     TIME_BEFORE_SWITCH 5,
		     DEBUG true);


query_forwarder :: SR2MetricFlood(ETHTYPE 0x0644,
			       IP $sr2_ip, 
			       ETH $wireless_mac, 
			       LT lt, 
			       ARP arp,
			       DEBUG false);

query_responder :: SR2QueryResponder(ETHTYPE 0x0645,
				    IP $sr2_ip, 
				    ETH $wireless_mac, 
				    LT lt, 
				    ARP arp,
				    DEBUG true);


query_responder -> SR2SetChecksum -> [0] output;
query_forwarder -> SR2SetChecksum -> SR2Print(forwarding) -> [0] output;
query_forwarder [1] -> query_responder;

data_ck :: SR2SetChecksum() 

input [1] 
-> host_cl :: IPClassifier(dst net $sr2_ip mask $sr2_nm,
				-)
-> querier
-> data_ck;


host_cl [1] -> [0] set_gw [0] -> querier;

forwarder[0] 
  -> dt ::DecIPTTL
  -> data_ck
  -> [2] output;


dt[1] 
-> Print(ttl-error) 
-> ICMPError($sr2_ip, timeexceeded, 0) 
-> querier;


// queries
querier [1] -> [1] query_forwarder;
es -> SetTimestamp() -> [1] output;


forwarder[1] //ip packets to me
  -> SR2StripHeader()
  -> CheckIPHeader()
  -> from_gw_cl :: IPClassifier(src net $sr2_ip mask $sr2_nm,
				-)
  -> [3] output;

from_gw_cl [1] -> [1] set_gw [1] -> [3] output;

 input [0]
   -> ncl :: Classifier(
			12/0643 , //sr2_forwarder
			12/0644 , //sr2
			12/0645 , //replies
			12/0641 , //sr2_es
			12/062c , //sr2_gw
			);
 
 
 ncl[0] -> SR2CheckHeader() -> [0] forwarder;
 ncl[1] -> SR2CheckHeader() -> PrintSR(query) -> query_forwarder
 ncl[2] -> SR2CheckHeader() -> query_responder;
 ncl[3] -> es;
 ncl[4] -> SR2CheckHeader() -> gw;
 
}



Idle -> s :: sr2(2.0.0.1, 255.0.0.0, 00:00:00:00:00:01, false, "12 60 12 1500") -> Discard;
Idle -> [1] s;
s[1] -> Discard;
s[2] -> Discard;
s[3] -> Discard;

Feature	Supported	Token	Example
Booleans	✓	true false
Comments	✓		// A comment
Line Comments	✓	//	// A comment
Semantic Indentation	X

Click - Programming language

Language features