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Show 21 tha t environment. The effort at Computervision resulted in a tool which worked well, but lack of speed and excessive rigidity caused its abandonment. graphical "techniques used so far. It presented the advanced It could enforce placement restrictions, expand and shrink the size or the SLA program and contained all the tools necessary ror generating composite layouts. The Computervision system remains, perhaps, the best simple graphical editor for SLA and PPL programs. The general failure of graphical SLA editors (with the possible exception of the PSI editor which is still under intensive development) led to the idea that one should approach the problem from a linguistic direction. ABLE (an Array-Based Linguistic Editor) was developed by Goates [20, 21, 22J at the University of Utah and is being pursued by Goates at Boeing and the University of Washington. While ABLE substantiated the validity of linguistic approaches to the problem of SLA layout, it was still only marginally removed from the capabilities of signal-aligning and sense inversion (changing O's to , 's and vice versa), as well as macro expansion (a capability that already existed on Computervision), but was still restricted in that it did not lend itself to true systems -design and produced no useful output. 2. SLA and PPL Compilers Certain problems were never attacked in any SLA editor (except perhaps the PSI editor). One such problem is the automatic placement |
