This branch adds a ternary conditional expression to Go, equivalent to the ternary a ? b : c expression found in the C programming language.
The syntax for Go is:
a then b else c
I originally wanted the expression to be of the form if a then b else c in a naturally readable way but adding the if prefix caused many shift/reduce conflicts in the go.y yacc grammar source causing conflicts with the if statement. I did not want to spend time trying to resolve these conflicts so I dropped the if requirement and that solved all the conflicts.
Unfortunately, then is now a reserved keyword. Ideally I want it to be a non-reserved keyword. There was one conflict in the Go standard library in runtime/mgc.go which was using then as a variable name. Renaming the variable solved the conflict of course, but it would be better form to not reserve the word then, thus allowing it to be used as a variable name, provided that doesn't introduce any grammar conflicts. I think Go does not have any non-reserved keywords in the grammar so adding that ability to the lexer is probably more complex in terms of effort than I'm willing to invest.
Trivial functions like min and max can now become one-liners without requiring a full if/else statement and two body blocks:
func max(a, b int) int { return a > b then a else b }
More complex expressions can be used of course, so long as the then expression type exactly matches the else expression type.
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