When did the syntax for reading metadata change from C # ^ to ^?

Question

Currently (Clojure v1.6) you can give a hint type in two ways:

^floats xs 

 #^floats xs 

According to Clojure ^ floats vs # ^ floats? , the latter is obsolete syntax, and the former is the current preferred form.

When did this change happen?

Answer 1

A Brief History of Macro ^

• In Clojure v1.0, the ^ character is a "meta-reader macro." In other words, ^x was short for (meta x) . #^ used to associate metadata with an object. (See Macro Characters Documentation November 2009. )

• At some point, someone probably realized that the presence of special cases for #^ and ^ related to metadata was puzzling. They decided to abandon ^ in order to eventually replace #^ with ^ . In Clojure v1.1, the reader macro ^ officially deprecated . (See Macro Characters Documentation January 2010. )

• Here's a fix on April 26, 2010 on Github , which replaces the behavior of the old ^ with the behavior of #^ . (This is when #^ and ^ became synonymous.)

• In the release of Clojure v1.2 #^ deprecated in favor of ^ . (See Macro Characters Documentation August 2010. )

• They removed the last few instances of #^ from clojure.core back in 2013, sometime before the release of Clojure v1.6.