The following table shows how the standard operators are directly converted into routine calls.
Operator Routine ------------------------------------ expr1 + expr2 expr1.plus(expr2) expr1 - expr2 expr1.minus(expr2) expr1 * expr2 expr1.times(expr2) expr1 / expr2 expr1.div(expr2) expr1 ^ expr2 expr1.pow(expr2) expr1 % expr2 expr1.mod(expr2) expr1 < expr2 expr1.is_lt(expr2) expr1 = expr2 expr1.is_eq(expr2) - expr expr.negate ~ expr expr.not |
In addition to the unary and binary operators, there are additional operators that are defined in terms of a combination of the unary and binary operators
Operator Translation --------------------------------------- expr1 <= expr2 expr2.is_lt(expr1).not expr1 >= expr2 expr1.is_lt(expr2).not expr1 /= expr2 expr1.is_eq(expr2).not expr1 > expr2 expr2.is_lt(expr1) |
[1] Earlier versions of Sather 1.0 defined separate routines for each of these operators.
The form '[expression list]' is translated into a call on the routine aget. For instance,
a := [3,5]; -- Equivalent to a := aget(3,5); Used in the array class f := arr[2]; -- Equivalent to f := arr.aget(2); Used outside the array |
This is described in more detail later.
In addition to the above mentioned operators, it is possible to group expressions using plain parentheses, which have the highest precedence.
The precedence ordering shown below determines the grouping of the syntactic sugar forms. Symbols of the same precedence associate left to right and parentheses may be used for explicit grouping. Evaluation order obeys explicit parenthesis in all cases.
Strongest | . :: [] ()
| ^
| ~ unary -
| * / %
| + binary -
| < <= = /= >= >
Weakest | and or |
The >, >= and /= operators are not directly translated into their own routine. Rather, they are defined in terms of is_lt and is_eq.
Each of these transformations is applied after the component expressions have themselves been transformed.
'out' and 'inout' modes may not be used with the syntactic sugar expressions.
The '<=' and '>' expressions do not reverse the original left to right order of argument evaluation.
and' and or' are not listed as syntactic sugar for operations in BOOL'; this allows short-circuiting the evaluation of subexpression.
The aget and aset routines are meant to support array like indexed access and require at least one index argument.
Here's a formula written with syntactic sugar and the calls it is textually equivalent to. It doesn't matter what the types of the variables are; the sugar ignores types.
-- Written using syntactic sugar r := (x^2 + y^2).sqrt; -- Written without sugar r := (x.pow(2).plus(y.pow(2))).sqrt |