Iterator in Icon

In Icon programming language, iterator is very powerful. As a result, Programming Language Pragmatics dedicates a sub section to explain it. The following shows the complete running code corresponding to the code snippets in the book.

procedure main()
 write("=================================================")
 every i := 1 to 10 by 2 do {
  write(i)
 }
 write("=================================================")
 every i := 1 + upto(' ', "a ss ss") do {
  write(i)
 }
 write("=================================================")
 i := 1
 every write(i + upto(' ', "a ss ss"))
 write("=================================================")
 if 2 < 3 then {
  write("2 < 3")
 }
 write("=================================================")
 if (i := find("abc", "abcabcabc")) > 6 then {
  write(i)
 }
 write("=================================================")
 if (i := find("x", "xaax")) = find("x", "bxxx") then {
  write(i)
 } 
end

The following code explains the description at the end of the sub section. It is If the expression following suspend contains an invocation of a generator, then the subroutine will suspend repeatedly, once for each generated value.

# suspend is followed by a value
procedure FollowedByValue()
 i := 1
 while i <= 3 do {
  suspend i
        i +:= 1
 }
end

# suspend is followed by a generator expression
procedure FollowedByGenExpr()
 suspend(1|2|3)
end

# suspend is followed by a generator function invocation
procedure FollowedByGenFuncInvocation()
 suspend FollowedByValue() 
end

procedure main()
 write("=================================================")
 every write(FollowedByValue())
 write("=================================================")
 every write(FollowedByGenExpr())
 write("=================================================")
 every write(FollowedByGenFuncInvocation())
end