This simple calculator works on floating point numbers written with an optional exponent part (e). It supports basic operators: +, -, *, /, ^ (power), % (modulo), unary -. Sub-expression can be computed using parenthesis.
Mathematical constants pi and e are defined, as well as special values nan and inf, and a number of basic functions (abs, pow, sqrt, exp, log with optional base, sin, cos, tan).
The result of computing an expression can be assigned to a variable using >. A variable name starts with a letter, and is composed of letters, digit, and undescore _. Any name can be used as long as it is not the name of a predefined constant or function.
digit = ('0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9')
letter = ('a'..'z'|'A'..'Z'|'_')
number ::= digit+ ('.' digit+)? ('e' ('+'|'-')? digit+)?
name ::= letter+ (digit|letter)*
identifier ::= name ('(' (expr (',' expr)*)? ')')?
primary ::= number|identifier|('(' expr ')')
factor ::= primary ('^' primary)?
term ::= factor (('*'|'/'|'%') factor)*
expr ::= ('+'|'-')? term (('+'|'-') term)*
statement ::= expr ('>' name)