A system for providing a computer configured to read an immutable value for a variable; read the value of the variable at a specific timestamp, thereby providing an ability to create looping constructs; set a current or next value of a loop variable as a function of previous or current loop variables; read a set of all values that a variable will assume; push or scatter the values into collections; reduce the collections into a single value; display graphical node representations to indicate computed values next to corresponding source code lines in an editor, and edge representations to indicate dependencies between values; visualize data output by a given node; permit the user to reorder source code lines by dragging nodes; cache or memoize computed values, and reuse cached or memoized values to implement reactive programming, minimizing recomputation in response to changes to program or data.