Expr is a very simple integer expression calculator. Its grammar is as follows:
identifier := [A-Za-z_] [A-Za-z_0-9]*
variable := identifier
decimal_literal := [0-9]+
hex_literal := '0x' [0-9A-Fa-f]+
binary_literal := '0b' [0-1]+
octal_literal := '0o' [0-7]+
literal := decimal_literal | hex_literal | binary_literal | octal_literal
binary_op := '+' | '-' | '*' | '/' | '%' |
'<<' | '>>' |
'==' | '!=' | '<' | '>' | '<=' | '>=' |
'&&' | '||' |
'&' | '|' | '^'
unary_op := '!' | '~'
brackets := '(' atom ')'
unary := unary_op atom
function_call := itentifier brackets
atom := brackets | unary | literal | function_call
expr := atom ( binary_op atom )*
Very standard with two exceptions:
- There is no unary + or -.
- Function calls always take exactly 1 argument.
The only supported types are bool and u64. There is no type coersion.
All arithmetic operations are checked and cause an error on over/underflow. Shift overflows (e.g. 1 << 100) are allowed and result in 0.
Operator meaning and precedence is the same as in Rust, with the exception of ~ which is used for bitwise not (Rust uses ! for both logical and bitwise not).
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