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 # eva
 
-> a basic calculator REPL (WIP)
+a read-eval-print-loop, similar to `bc(1)`
+
+### installation
+
+```shell
+$ git clone https://github.com/nerdypepper/eva.git
+$ cargo run
+```
+
+### usage
+
+```shell
+$ eva
+```
+
+type out an expression and hit enter, repeat.
+
+```shell
+1 + sin(30)
+ans: 1.5
+
+floor(sqrt(3^2 + 5^2))
+ans: 5
+
+5sin(45) + cos(0  # eva will try to autobalance braces
+ans: 3.4999999999999996
+```
+
+### operators
+
+ - binary operators: `+ - * / ^`
+ - unary operators: `+ -`
+
+### functions
+
+all trignometric functions expect input in degrees.  
+conversion to radians is to be done manually (` x * 3.14 / 180`)
+
+```
+sin  
+cos  
+tan  
+csc     # cosec is for pesants
+sec  
+cot  
+sinh 
+cosh 
+tanh 
+ln      # log to the base e
+log     # log to the base 10
+sqrt    # x ^ 0.5
+ceil 
+floor
+```
+
+examples:  
+```
+sqrt(sin(30)) # parenstheses are mandatory for functions
+
+log100        # no
+log(100)      # yes
+```
+
+### quality of life features
+
+auto insertion of `*` operator
+```
+12sin(90)  # 12 * sin(90)
+ans: 12
+
+(5 + 6)(6 + 7)  # (5 + 6) * (6 + 7)
+ans: 143
+
+11(12)  # 11 * (12)
+ans: 132
+```
+
+auto balancing of parentheses
+```
+ceil(sqrt(3^2 + 5^2
+ans: 6
+```
 
 ### todo
 
  - add detailed error handler
  - multiple arg functions
- - unary operators (minus, factorial)
- - lineeditor with syntax highlighting
+ - ~~unary operators (minus, factorial)~~
+ - lineditor with syntax highlighting
+ - ~~add more functions~~