---++ Syntax
"if" Strategy "then" Strategy "else" Strategy "end" -> Strategy
---++ Description
t
If =s1= succeeds then strategy =s2= is applied. If =s1= fails, then =s3= is applied.
The result of condition is ignored. If the condition succeeds, then the result is
t
If the condition fails, then the result is
t
---++ Formatting
The if then else construct is usally formatted in the following way:
if s1 then
s2
else
s3
end
---++ Implementation
The if-then-else construct is sugar for a guarded left-choice. The
strategy
if s1 then s2 else s3 end
translates into
where(s1) < s2 + s3