using CP;
 
 dvar interval input size 2;
 dvar interval output size 2;
 
 stateFunction s;
 
 subject to
 {
   alwaysEqual(s,input,1);
   alwaysEqual(s,output,1);
 
   startOf(input)==1;
   startOf(output)==8;
 }

execute
{ 

  writeln(s);
 
} 

gives

stepwise{ -1 -> 1; 1 -> 3; -1 -> 8; 1 -> 10; -1 }

But you can use a new interval which contains both intervals and then you do not get the -1 state in the middle

using CP;
 
 dvar interval input size 2;
 dvar interval output size 2;
 
 dvar interval inputoutput;
 
 stateFunction s;
 
 subject to
 {
   alwaysEqual(s,inputoutput,1);
   startAtStart(inputoutput,input);
   endAtEnd(inputoutput,output);
   
   
 
   startOf(input)==1;
   startOf(output)==8;
 }

execute
{ 

  writeln(s);
 
} 
 

which gives

stepwise{ -1 -> 1; 1 -> 10; -1 }

 using CP;  dvar interval input size 2; dvar interval output size 2;  stateFunction s;  subject to {   alwaysEqual(s,input,1);   alwaysEqual(s,output,1);    startOf(input)==1;   startOf(output)==8; }execute{   writeln(s); } 

gives

stepwise{ -1 -> 1; 1 -> 3; -1 -> 8; 1 -> 10; -1 }

But you can use a new interval which contains both intervals and then you do not get the -1 state in the middle

using CP;  dvar interval input size 2; dvar interval output size 2;  dvar interval inputoutput;  stateFunction s;  subject to {   alwaysEqual(s,inputoutput,1);   startAtStart(inputoutput,input);   endAtEnd(inputoutput,output);          startOf(input)==1;   startOf(output)==8; }execute{   writeln(s); }  

which gives

stepwise{ -1 -> 1; 1 -> 10; -1 }