SHRDLU

A port of Terry Winograd's 1970 SHRDLU natural language / blocks world program, targeting CLISP (Common Lisp). Originally written in Maclisp for a PDP-10; this version was ported at the University of Missouri-Rolla (UMR) around 2000 and carries the internal version tag UMR-1.0.

Requirements

• CLISP 2.49 or later (ARM64 macOS: brew install clisp)

Running

From the repo root:

clisp LOADER

CLISP loads all source files, initializes the blocks world, and prints READY. Type English sentences one per line.

READY
WHAT BLOCKS ARE ON THE TABLE?
THE BLUE ONE ,THE GREEN CUBE ,THE LARGE RED ONE ,THE LARGE GREEN ONE
WHICH SUPPORTS THE RED PYRAMID ,AND THE RED CUBE .

READY
PICK UP A BIG RED BLOCK.
~MOVING HAND TO (100 340 500)~
~GRASPING BLOCK B7~
~MOVING HAND TO (600 1100 200)~
~LETTING GO~
OK .

READY
FIND A BLOCK WHICH IS TALLER THAN THE ONE YOU ARE HOLDING AND PUT IT INTO THE BOX.
~CHOOSING BLOCK B10~
...
OK .

The ~MOVING HAND TO ...~ lines are the physical simulator narrating the robot arm. There is no graphical display — text mode only.

Notes

• Use "A RED BLOCK" (indefinite), not "THE RED BLOCK" (definite) when multiple candidates exist. Definite reference to an ambiguous object gets "I DON'T KNOW WHICH ONE YOU MEAN."
• Don't type OK as input — SHRDLU doesn't recognize it. It expects natural language sentences.
• Redefinition warnings during startup (redefining function LIS2FY ...) are harmless.

Further reading

• Winograd's original 1972 paper
• Kent Pitman's MacLisp manual — reference for Maclisp→Common Lisp compatibility issues
• Miles Davis's UMR Project notes
• SHRDLU resurrection (copy)