. . . . . . recurse: # else # return n*fact(n-1); sub $a0,$s1,1 # argument0 = n-1 # subroutine call # 1. No T registers to push # 2. Argument is in $a0 jal fact # 3. Jump and link to subroutine mul $v0,$v0,$s1 # n*fact(n-1) epilog: # epilog # 1. Return value is already in $v0 . . . . . . jr $ra #
Recursion has been implemented by using: (1) the normal machine operations of sequential execution, testing, and branching, and (2) the run-time stack.
This is (yet another) example of a new level of abstraction being build upon a foundation level. Have I mentioned that this is one of the most stunningly important ideas of Computer Science?
The programming language FORTRAN IV did not have support for recursion. Was it possible to write a recursive program in FORTRAN IV?