Click - Programming language

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Click is an open source programming language created in 1999.

#329on PLDB

25Years Old

39Repos

Download source code:

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

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The Click modular router: fast modular packet processing and analysis

Tags: programming language
Click is developed on GitHub and has 733 stars
There are at least 39 Click repos on GitHub
Early development of Click happened in MIT
Click is written in C++, C, Perl, Bourne shell, Make, Java, M4, Diff, YAML, Tex, Markdown, Dockerfile, Vim script, XSLT, Yacc, DTD, XML
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;

Language features

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