********** source program **********
fn main () -> Int {
var Int: x = 0;
return x;

}
********** type checking **********
--- step exp Int --->
--- step exp Int --->
--- step exp Int --->

********** type checking complete **********
fn main () -> Int {
var Int: x = 0;
return x;
}
********** starting execution **********
********** initializing globals **********
--- step exp () --->
********** calling main function **********
{
stack: top{main()<-1>}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp main() --->
{
stack: top{main<-1> :: main()<0>}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp main --->
{
stack: top{fun<main><-1> :: main()<0>}
heap: fun<main>, 
env: main: fun<main>, 
}
--- handle value fun<main> with main()<1>(fun<main>,) --->
{
stack: top{()<-1> :: main()<1>(fun<main>,)}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp () --->
{
stack: top{()<-1> :: main()<1>(fun<main>,)}
heap: fun<main>, 
env: main: fun<main>, 
}
--- handle value () with main()<2>(fun<main>,(),) --->
pattern_match((), ())
{
stack: main{var Int: x = 0; ... <-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step stmt var Int: x = 0; ...  --->
{
stack: main{var Int: x = 0;<-1> :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step stmt var Int: x = 0; --->
{
stack: main{0<-1> :: var Int: x = 0;<0> :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp 0 --->
{
stack: main{0<-1> :: var Int: x = 0;<0> :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- handle value 0 with var Int: x = 0;<1>(0,) --->
{
stack: main{Int: x<-1> :: var Int: x = 0;<1>(0,) :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp Int: x --->
{
stack: main{Int<-1> :: Int: x<0> :: var Int: x = 0;<1>(0,) :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- step exp Int --->
{
stack: main{Int<-1> :: Int: x<0> :: var Int: x = 0;<1>(0,) :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- handle value Int with Int: x<1>(Int,) --->
{
stack: main{Int: x<-1> :: var Int: x = 0;<1>(0,) :: return x;<-1>} :: top{}
heap: fun<main>, 
env: main: fun<main>, 
}
--- handle value Int: x with var Int: x = 0;<2>(0,Int: x,) --->
pattern_match(Int: x, 0)
{
stack: main{return x;<-1>} :: top{}
heap: fun<main>, 0, 
env: x: 0, main: fun<main>, 
}
--- step stmt return x; --->
{
stack: main{x<-1> :: return x;<0>} :: top{}
heap: fun<main>, 0, 
env: x: 0, main: fun<main>, 
}
--- step exp x --->
{
stack: main{0<-1> :: return x;<0>} :: top{}
heap: fun<main>, 0, 
env: x: 0, main: fun<main>, 
}
--- handle value 0 with return x;<1>(0,) --->
{
stack: top{0<-1>}
heap: fun<main>, !!0, 
env: main: fun<main>, 
}
result: 0