Add documentation (#47)

* Add documentation

* Fix docstrings

Author: devmotion

README.md

@@ -29,7 +29,7 @@ Irrational{:twoπ}
 
 Note: to input the τ character, type `\tau` then press <kbd>Tab</kbd>.
 
-The tau variants of `sinpi`, `cospi`, and `mod2pi` are also defined:
+The tau variants of `sinpi`, `cospi`, `sincospi`, `cispi`, and `mod2pi` are also defined:
 
 ```julia
 julia> sintau(1//4)
@@ -38,11 +38,17 @@ julia> sintau(1//4)
 julia> costau(1//2)
 -1.0
 
+julia> sincostau(1//2)
+(0.0, -1.0)
+
+julia> cistau(1//2)
+-1.0 + 0.0im
+
 julia> modtau(9*pi/4)
 0.7853981633974481
 ```
 
-Alternatively, one can use the Unicode aliases `sinτ`, `cosτ`, and `modτ`.
+Alternatively, one can use the Unicode aliases `sinτ`, `cosτ`, `sincosτ`, `cisτ`, and `modτ`.
 
 ## The tau != 2pi inequality
 

src/Tau.jl

@@ -45,9 +45,54 @@ function cisτ(x::Integer)
     return complex(one(y), zero(y))
 end
 
+# Aliases
 const sintau = sinτ
 const costau = cosτ
 const sincostau = sincosτ
 const cistau = cisτ
 
+# Documentation
+
+"""
+    sinτ(x)
+    sintau(x)
+
+Compute ``\\sin(\\tau x)`` more accurately than `sin(tau*x)`, especially for large `x`.
+
+See also: `costau`, `sincostau`.
+"""
+function sinτ end
+
+"""
+    cosτ(x)
+    costau(x)
+
+Compute ``\\cos(\\tau x)`` more accurately than `cos(tau*x)`, especially for large `x`.
+
+See also: `sintau`, `sincostau`.
+"""
+function cosτ end
+
+"""
+    sincosτ(x)
+    costau(x)
+
+Simultaneously compute `sintau(x)` and `costau(x)` (the sine and cosine of `tau*x`,
+where `x` is in radians), returning a tuple `(sine, cosine)`.
+
+See also: `sintau`, `costau`.
+"""
+function sincosτ end
+
+
+"""
+    cisτ(x)
+    cistau(x)
+
+Compute ``\\exp(\\tau i x)`` more accurately than `cis(tau*x)`, especially for large `x`.
+
+See also: `cis`, `sincostau`.
+"""
+function cisτ end
+
 end