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History

TREE-META was instrumental in the development of NLS (oN-Line System) and was ported to many systems including the UNIVAC 1108, GE 645, SDS 940, ICL 1906A, PERQ, and UCSD p-System.²³

Example

This is a complete example of a TREE-META program extracted (and untested) from the more complete (declarations, conditionals, and blocks) example in Appendix 6 of the ICL 1900 TREE-META manual.⁴ That document also has a definition of TREE-META in TREE-META in Appendix 3. This program is not only a recognizer, but also outputs the assembly language for the input. It demonstrates one of the key features of TREE-META, which is tree pattern matching. It is used on both the LHS (GET and VAL for example) and the RHS (ADD and SUB).

% This is an ALGOL-style comment delimited by %

% ====================== INPUT PARSE RULES ======================= % .META PROG % A program defining driving rule is required.  % % This PROG rule is the driver of the complete program.  % PROG = $STMT ; % $ is the zero or more operator.  % % PROG (the program) is defined as zero or more STMT (statements). % STMT = .ID ':=' AEXP :STORE[2]*; % Parse an assignment statement from the source to the tree.  % % ':=' is a string constant, :STORE creates a STORE node,  % % [2] defines this as having two branches i.e. STORE[ID,AEXP].  % % * triggers a unparse of the tree, Starting with the last created % % tree i.e. the STORE[ID,AEXP] which is emitted as output and  % % removed from the tree.  % AEXP = FACTOR $('+' FACTOR :ADD[2] / '-' FACTOR :SUB[2]); % Here we have the recognizer for arithmetic '+' :ADD and '-' :SUB % % tree building. Again the [2] creates a 2-branch ADD or SUB tree. % % Unparsing is deferred until an entire statement has been parsed. % % ADD[FACTOR,FACTOR] or SUB[FACTOR,FACTOR]  % FACTOR = '-' PRIME :MINUSS[1] / PRIME ; PRIME = .ID / .NUM / '(' AEXP ')' ?3? ; % ?3? is a hint for error messages.  % % ===================== OUTPUT UNPARSE RULES ===================== % STORE[-,-] => GET[*2] 'STORE ' *1 ; % *1 is the left tree branch. *2 is the right  % % GET[*2] will generate code to load *2.  % % The 'STORE' string will be output  % % followed by left branch *1 a symbol  % % Whatever *2, it will be loaded by GET[*2].  % GET[.ID] => 'LOAD ' *1 / [.NUM] => ' LOADI ' *1 / [MINUSS[.NUM]] => 'LOADN ' *1:*1 / [-] => *1 ; % Here an .ID or a .NUM will simply be loaded. A MINUSS node  % % containing a .NUM will have this used, the notation *1:*1 means  % % the first branch (a .NUM) of the first branch (MINUSS).  % % Anything else will be passed on for node recognition  % % The unparse rules deconstruct a tree outputing code.  % ADD[-,-] => SIMP[*2] GET[*1] 'ADD' VAL[*2] / SIMP[*1] GET[*2] 'ADD' VAL[*1] / GET[*1] 'STORE T+' < OUT[A] ; A<-A+1 > / GET[*2] 'ADD T+' < A<-A-1 ; OUT[A] > ; % Chevrons < > indicate an arithmetic operation, for example to  % % generate an offset A relative to a base address T.  % SUB[-,-] => SIMP[*2] GET[*1] 'SUB' VAL[*2] / SIMP[*1] GET[*2] 'NEGATE' % 'ADD' VAL[*1] / GET[*2] 'STORE T+' < OUT[A] ; A<-A+1 > / GET[*1] 'SUB T+' < A<-A-1 ; OUT[A] > ; % A percent character in an unparse rule indicates a newline.  % SIMP[.ID] => .EMPTY / [.NUM] => .EMPTY / [MINUSS[.NUM]] => .EMPTY; VAL[.ID] => ' ' *1 / [.NUM] => 'I ' *1 / [MINUSS[.NUM]] => 'N ' *1:*1 ; MINUSS[-] => GET[*1] 'NEGATE' ; .END

See also

• NLS (computer system)
• META II

• C. Stephen Carr, David A. Luther, Sherian Erdmann, The TREE-META Compiler-Compiler System: A Meta Compiler System for the Univac 1108 and General Electric 645, University of Utah Technical Report RADC-TR-69-83.
• Englebart, D. C .; English, W. K.; Rulifson, J . F. (April 1968). Development of a Multidisplay, Time-shared Computer Facility and Computer-augmented Management-system Research (PDF). Menlo Park, California: Stanford Research Institute. Prepared for Rome Air Development Center, Griffiss Air Force Base, New York, New York. And alternate website. A report on Tree Meta's use in what they called Special-Purpose Languages (SPL), which are now called Domain Specific Languages (DSL), in the oN-Line System
• Donald I. Andrews, J. F. Rulifson (1967). Tree Meta (Working Draft): A Meta Compiler for the SDS 940, Stanford Research Institute, Menlo Park, CA. Engelbart Collection, Stanford University Archive, M 638, Box 16, Folder 3.
• Andrews, Lehtman, and WHP. "Tree Meta – a metacompiler for the Augmentation Research Center". Preliminary draft, 25 March 1971.
• Alan C. Kay The Reactive Engine Ph.D. thesis 1969 University of Utah. Notes that Henri Gouraud did the FLEX compiler in TREE-META on the SRI (Engelbart) SDS-940.
• Atlas Computer Laboratory quarterly report (21 November 1975), F. R. A. Hopgood documents work using TREE-META to create a compiler generating FR80 assembler output.
• Atlas Computer Laboratory quarterly report (12 October 1973), C. J. Pavelin documents (section 4.10) TREE-META being ported to the 1906A.
• TREE-META: a meta-compiler for the Interdata Model 4 by W. M. Newman. Queen Mary College, London. November 1972.

External links

• TREE-META on GitHub, coded in C, based on ICL 1900 version
• TREE-META compiler-compiler revival on GitHub
• Manual for ICL 1900 version of TREE-META by F R A Hopgood.
• Wiki for collecting information about TREE-META
• TREE META Draft Document December, 1967 at bitsavers.org
• TREE META Release Document April, 1968 at bitsavers.org
• Study for the Development of Human Intellect Augmentation Techniques, by D. C. Engelbart

References

1. Donald I. Andrews, J. F. Rulifson (1967). Tree Meta (Working Draft): A Meta Compiler for the SDS 940, Stanford Research Institute, Menlo Park, CA. Engelbart Collection, Stanford University Archive, M 638, Box 16, Folder 3. /wiki/Jeff_Rulifson ↩

2. Bowles, K. L., 1978. A (nearly) machine independent software system for micro and mini computers. SIGMINI Newsl., 4(1), 3–7. doi:10.1145/1041256.1041257 /wiki/Doi_(identifier) ↩

3. Bowles, K. L. (May 1978). "UCSD Pascal: A (nearly) machine independent software system for micro and mini computers". Byte. Vol. 3, no. 5. pp. 46, 170–173 – via Internet Archive.{{cite magazine}}: CS1 maint: date and year (link) https://archive.org/stream/byte-magazine-1978-05-rescan/1978_05_BYTE_03-05_Graphics_in_Depth#page/n47/mode/1up ↩

4. Hopgood, F. R. A. 1974, "TREE-META Manual", Atlas Computer Laboratory. ↩